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Field Crops Research

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Progressive integrative crop managements increase grain yield, nitrogen useefficiency and irrigation water productivity in rice

Hao Zhang, Chao Yu, Xiangsheng Kong, Danping Hou, Junfei Gu, Lijun Liu, Zhiqin Wang,Jianchang Yang⁎

Jiangsu Key Laboratory of Crop Genetics and Physiology, Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou, China

A R T I C L E I N F O

Keywords:Rice (Oryza sativa L.)Integrative crop managementNitrogen use efficiencyIrrigation water productivityGrain yield

A B S T R A C T

It is a major challenge to achieve the goal of increasing grain yield, nitrogen use efficiency (NUE) and irrigationwater productivity (IWP) in cereals. This study investigated if progressive integrative crop management tech-nology in rice (Oryza sativa L.) could improve agronomic and physiological performances, and consequently,increase grain yield, NUE and IWP. A japonica rice cultivar and an indica-japonica hybrid rice cultivar weregrown in the field, with five crop managements including an unfertilized 0 N treatment (0 N), local farmer’spractice (LFP), integrative crop management (ICM) 1–3 ((ICM1, ICM2, and ICM3)). The results showed that,when compared to LFP, the ICM could not only increase grain yield, NUE and IWP, but also improve agronomicand physiological performances. Both ICM1 and ICM2 increased economic benefit. The progressive effect on theyield, NUE, IWP, and agronomic and physiological performance was obvious with the progressive introductionof single cultivation technology. The ICM increased sink size (total number of spikelets), percentage of pro-ductive tillers, leaf area index and duration, crop growth rate, non-structural carbohydrate accumulation andremobilization, leaf photosynthetic rate, root dry weight and length, root oxidation activity, root bleeding, andzeatin and zeatin riboside content in roots and leaves. The results suggest that the integrative and optimized cropmanagement could achieve the dual goal of increasing grain yield and resource use efficiency through improvingagronomic and physiological performances, especially increases in sink size and shoot and root growth, leadingto higher grain yield, NUE, and IWP.

1. Introduction

Rice (Oryza sativa L.) is one of the most important staple cerealcrops in the world, and more than half of the world’s population de-pends on rice for food calories and protein, especially in developingcountries (Godfray et al., 2010; Khush, 2001). It is estimated that by theyear 2025, it will be necessary to increase rice production by ap-proximately 60% over current levels, corresponding to annual increasesin yield of at least 1.2% per year (Normile, 2008). In the last half-century, world rice production has dramatically increased, primarily asthe result of genetic improvement: increasing harvest index by use ofthe semi-dwarf gene and utilization of heterosis by producing hybrids(Peng et al., 1999; Zhang, 2007, 2011). Rice grain yield in China hasbeen over 6 ton per hectare in recent years which is 65% higher thanthat of the world average (FAOSTAT, 2012). However, in the past 10years, rice yield increase eventually slowed in China as well as in othercountries. The average increase in yield dropped below 1% annually(Katsura et al., 2007; Normile, 2008). Great effort should be made to

maximize grain yield with improved resource use efficiency.Nitrogen (N) is one of the main factors determining crop yield and

has made great contribution to the increase in rice yield in the last halfcentury (Ju et al., 2015; Peng et al., 2010; Yoshiaki et al., 2011; Zhanget al., 2012a,b; Chen et al., 2014). However, oversupply of synthetic Nfertilizer has become widespread in China. The Chinese nationalaverage N application rate in rice is 180 kg N ha−1, which is 75%higher than the global average. It is reported that the agronomic N useefficiency of farmers’ practice was 6.4 kg kg−1 and 5−10 kg kg−1 inZhejiang and Jiangsu Provinces, respectively (Wang et al., 2001; Penget al., 2006, 2010). In the Taihu lake region, the N rate reached360 kg N ha−1, and the use of N fertilizer is inefficient (Ju et al., 2015;Miao et al., 2010; Zhao et al., 2012). The low nitrogen use efficiency(NUE) has not only decreased the stability of the rice grain yield, butalso raised concerns about environmental sustainability, and theseoutcomes lead to water eutrophication (Guo et al., 2010; Chen et al.,2015; Azusa et al., 2016). Increasing grain yield and NUE in ricewithout increasing N application is a major challenge.

http://dx.doi.org/10.1016/j.fcr.2017.09.034Received 8 June 2017; Received in revised form 25 September 2017; Accepted 28 September 2017

⁎ Corresponding author.E-mail address: jcyang@yzu.edu.cn (J. Yang).

Field Crops Research 215 (2018) 1–11

0378-4290/ © 2017 Elsevier B.V. All rights reserved.

MARK

Rice is also the greatest consumer of water among all crops andconsumes approximately 80% of the total irrigated fresh water re-sources in Asia (Tuong et al., 2005). Declining quality of water anddeclining availability of water resources are threatening the sustain-ability of the irrigated rice-based production system (Rijsberman,2006). Exploring approaches to produce more rice with high irrigationwater productivity (IWP) is essential for food security and sustainingenvironmental health. A number of irrigation water saving technologieshave been developed to reduce irrigation input, increase IWP, andmaintain or increase production for rice-based systems, such as anaerobic rice system (Bouman et al., 2005; Lampayan et al., 2010), asystem of rice intensification (Zhao et al., 2009), non-flooded mulchingcultivation (Tao et al., 2006; Zhang et al., 2009a,b,c), and alternatewetting and drying (AWD) irrigation (Bouman and Tuong, 2001; Belderet al., 2007; Zhang et al., 2012a,b). Among these technologies, AWDhas been mostly applied in Asian countries such as China, Bangladesh,India, and Vietnam (Kukal et al., 2005; Tuong et al., 2005; Bouman,2007). It has been reported that, when compared with continuouslysubmerged conditions, AWD can maintain or even increase grain yield(Tuong et al., 2005; Lampayan et al., 2015). On the other hand, thereare reports that AWD often reduces, rather than increases, grain yieldwhen compared with continuously submerged conditions (Tabbal et al.,2002; Belder et al., 2004). Obviously, it remains a major challenge toreduce irrigation water input without compromising yield and to op-timize water management in rice production.

High yield and high NUE and IWP are urgent requirement in currentagricultural production, especially in developing countries. Can ahigher yield and higher NUE and IWP be achieved through integratingand optimizing cultivation techniques in rice production? Althoughthere were studies on the integrating and optimizing crop cultivationmanagements, these mainly focused on yield and agronomic perfor-mance of rice between integrative crop management and currentfarmers’ practices (Tilman et al., 2002; Martin and Malcolm, 2010; Suiet al., 2013; Xue et al., 2013; Chen et al., 2014; Wang et al., 2016).Little is known about the progressive effect of progressive integrativecrop managements on agronomic and physiological performance inrice. The purposes of this study were to (i) compare agronomic per-formance under progressive integrative crop managements, includingtiller number, leaf area index (LAI), non-structural carbohydrate (NSC)remobilization, leaf area duration (LAD), crop growth rate (CGR), androot dry weight and length, (ii) investigate the yield performance, NUEand IWP, and (iii) understand the physiological mechanism of theprogressive effect under integrative crop managements by measuringleaf photosynthetic rate, root oxidation activity (ROA), root bleeding,and zeatin (Z) + zeatin riboside (ZR) content.

2. Materials and methods

2.1. Plant materials and cultivation

Field experiment was conducted at research farm of YangzhouUniversity, Jiangsu Province, China (32°30′N, 119°25′E) during the ricegrowing season (May to October) of 2015, and repeated in 2016. Thesoil was a sandy loam (Typic fluvaquents, Etisols, U.S. classification)with 23.2 g kg−1 organic matter, 95.2 mg kg−1 alkali hydrolysable N,22.5 mg kg−1 Olsen-P, and 82.6 mg kg−1 exchangeable K. The soilmoisture content was 0.192 g g−1 at field capacity, and bulk density ofthe soil was 1.30 g cm−3. The average air temperature, sunshine hours,and precipitation during the rice growing season across the two yearsmeasured at a weather station close to the experimental site are shownin Fig. 1.

A japonica rice (Oryza sativa L.) cultivar Wuyunjing 24 (W24) and anindica-japonica hybrid rice cultivar Yongyou 2640 (Y2640), which werecurrently used in local production, were grown in the field. Across thetwo years, seedlings were raised in the seedbed with sowing date on 12May and transplanted on 12 June at different management practices of

different planting densities, N rates, tillage depth, and irrigation man-agements (Table 1). Weeds, insects, and diseases were controlled byeither chemical or manual methods to avoid yield loss. The headingdate (50% plants) for W24 was on 23–25 August and for Y2640 on 5–12August across the two years. Plants were harvested on 18–20 October.

2.2. Treatments

The experiment was laid out in a randomized complete block designwith three replications. Plot dimensions were 5 by 6 m and plots wereseparated by an alley of 1 m wide with plastic film inserted into the soilto a depth of 0.50 m to form a barrier. Phosphorus (30 kg ha−1 as singlesuperphosphate) and potassium (40 kg ha−1 as KCl) were applied andincorporated before transplanting as basal fertilizer. Rice seedlingswere transplanted with two seedlings per hill. Five treatments, in-cluding an unfertilized 0 N treatment (0 N), local farmer’s practice(LFP), integrative crop management 1 (ICM1), integrative crop man-agement 2 (ICM2), and integrative crop management 3 (ICM3), wereshown in Table 1.

In the 0 N plots, no nitrogen was applied. Rice seedlings weretransplanted at a hill spacing of 16 × 25 cm. The tillage depth was10 cm and the irrigation management was continuously flooded (CF).Except drainage at the mid-season, the continuously flooded regimemaintained a continuous flood with 2–3 cm water depth until one weekbefore the final harvest (Table 1).

Fig. 1. Precipitation (A), sunshine hours (B), and temperature (C) during the growingseason of rice in 2015 (solid lines) and 2016 (dotted lines) at the experiment site ofYangzhou, Southeast China. Data are means of per 10 days from the transplanting of rice.

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In the LFP, the crop management was conducted usually in YangtzeRiver Basin area, and 300 kg N ha−1 was applied with ratio of 5:2:2:1 atpre-transplanting, mid tillering, panicle initiation, and spikelet differ-entiation stage, respectively. Plant density, tillage depth and irrigationmanagement were the same as those in the 0 N plots (Table 1).

In the ICM1, 270 kg N ha−1 was applied with ratio of 4:2:2:2 at pre-transplanting, mid tillering, panicle initiation, and spikelet differ-entiation stage, respectively. Rice seedlings were transplanted at a hillspacing of 12.8 × 25 cm. Inorganic N application stage, tillage depthand irrigation management were the same as those in the LFP (Table 1).

ICM2 was based on the ICM1. Irrigation management of alternatewetting and moderate soil drying (AWMD) was introduced. In theAWMD regime, fields were not irrigated until soil water potentialreached −15 kilopascal (kPa) (soil moisture content 0.170 g g−1) at15–20 cm depth. Soil water potential of −15 kPa in the AWMD regimewas chosen because our earlier work (Yang et al., 2007; Zhang et al.,2009a,b,c) showed that a mild soil-drying regime (soil water potential−15 kPa at 15–20 cm depth) during the growing season did not reducegrain yield when compared to the CF regime. Soil water potential wasmonitored at 15–20 cm soil depth with a tensionmeter consisting of asensor of 5 cm length. Four tensionmeters were installed in each plot ofAWMD regimes, and readings were recorded at 1200 h each day. Whensoil water potential reached the threshold, a flood with 2.0–2.5 cmwater depth was applied to the plots. The amount of irrigation waterwas monitored with a flow meter (LXSG-50 Flow meter, ShanghaiWater Meter Manufacturing Factory, Shanghai, China) installed in theirrigation pipelines. Both irrigation and drainage systems were builtbetween blocks. Each plot was irrigated or drained independently. In-organic N application rate and stage, plant density and tillage depthwere the same as those in the ICM1 (Table 1).

In ICM3, rapeseed cake was applied in addition to inorganic ferti-lizer as in ICM2. The rapeseed cake fertilizer was a byproduct of ra-peseed after pressing oil. The content of N, phosphorus, potassium, andorganic matter are 5.00%, 1.05%, 1.20%, and 81.60% respectively.Inorganic N application rate and stage, plant density, irrigation man-agement and tillage depth were the same as those in the ICM2(Table 1).

2.3. Sampling and measurements

Twenty plants in each plot were tagged for observation of tillernumber. The observation was made at transplanting, mid tillering,panicle initiation, heading time (50% of plant headed), and maturity.The percentage of productive tillers was defined as the number of pa-nicles developed from tillers as a percentage of the number of tillersobserved at the panicle initiation stage.

To ensure representativeness of the sampling, the number of stemsin 100 hills were counted at each plot, and then plants of 12 hills withthe mean stem number were sampled for measurements of root andshoot biomass, leaf area, root length, root oxidation activity (ROA), andZ + ZR contents in roots and leaves at mid tillering, panicle initiation,heading time, and maturity. To maintain canopy conditions, the vacantspaces left after sampling for measurements of root and shoot biomasseswere immediately replaced with hills taken from the borders, and thesereplanted hills were not subjected to any further sampling.

For each root sampling, a cube of soil (20 cm× 20 cm× 20 cm)around each individual hill was dug up using a sampling core. The rootswere carefully rinsed with hydropneumatic elutriation device(Gillison’s Variety Fabrications, Benzonia, MI) and detached from theirnodal bases. Such a cube contains approximately 95% of total rootbiomass (Kukal and Aggarwal, 2003; Yang et al., 2008). About 10 groots from each sample were frozen in liquid N for 1 min and thenstored at −80 °C for hormonal assay. Portions of each root sample wereused for measurements of root length and ROA. The rest of the rootswere dried in an oven at 70 °C to constant weight and weighed. Tomeasure root length, roots were arranged and floated on shallow waterin a glass tray (30 cm× 30 cm) and then scanned using a scanner(Epson Expression 1680 Scanner, Seiko Epson Corp., Tokyo, Japan) andanalyzed using WinRHIZO Root Analyzer System (Regent InstrumentsInc., Quebec, Canada). The ROA was determined by measuring oxida-tion of alpha-naphthylamine (α-NA) according to the methods ofRamasamy et al. (1997), and was expressed as μg α-NA per gram dryweight (DW) per hour (μg α-NA g−1 DW h−1).

Before root sampling, aboveground plant tissues were sampled andseparated into leaves, stems (culms +sheaths), panicles (at headingtime and maturity), and dead shoot parts. The dry weight of each

Table 1Crop management for different treatments.

Treatment a N application Plant density (cm × cm) Irrigation management b Organic fertilizer c (kg ha−1)

Growth stage N rate (kg N ha−1)

0 N All stages 0 16 × 25 CF –LFP Before transplanting 150 16 × 25 CF –

Mid tillering 60Panicle initiation 60Spikelet differentiation 30Total 300

ICM1 Before transplanting 108 12.8 × 25 CF –Mid tillering 54Panicle initiation 54Spikelet differentiation 54Total 270

ICM2 Before transplanting 108 12.8 × 25 AWMD –Mid tillering 54Panicle initiation 54Spikelet differentiation 54Total 270

ICM3 Before transplanting 108 12.8 × 25 AWMD 2250Mid tillering 54Panicle initiation 54Spikelet differentiation 54Total 270

a 0 N, LFP, ICM1, ICM2 and ICM3 represent no N application, local farmer’s practice, integrative crop management 1, integrative crop management 2, and integrative crop man-agement 3, respectively.b CF and AWMD represent continuous flooding and drainage at mid-tillering, and alternate wetting and moderate soil drying irrigation.c Organic fertilizer usedhere is rapeseed cake fertilizer (a byproduct of rapeseed after pressing oil).

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component was determined after drying at 70 °C for 72 h. The NSCcontent in the stem at heading and maturity was measured according tothe method described by Yoshida et al. (1976). After leaves were re-moved from the stem, leaf area was immediately measured with an areameter (LI-3000C, Li-Cor, Lincoln, NE). Leaf area duration (LAD) andcrop growth rate (CGR) were calculated using the following formulas:

= + −− L L t tLAD (m m d) 1

2( )( )2 2

1 2 2 1 (1)

=−

−

− −W W

t tCGR (gm d )2 1 2 1

2 1 (2)

Where L1 and L2 are the first and second measurements of leaf areaindex (m2 m−2), respectively, W1 and W2 are the first and secondmeasurements of shoot biomass (g m−2), respectively, and t1 and t2represent the first and second times of measurement (d), respectively.

Photosynthetic rate was measured at mid tillering, panicle initia-tion, heading time, and maturity. The photosynthetic rate of leaves wasmeasured with a gas exchange analyzer (Li-Cor 6400 portable photo-synthesis measurement system, Li-Cor). The measurement was madefrom 0900 to 1100 h, when photosynthetic active radiation above thecanopy was 1300–1500 μmol m−2 s−1. Eight leaves were used for eachtreatment.

The root bleeding sap was collected from plants at mid tillering,panicle initiation, heading time, and maturity. Five plants chosen ineach treatment were cut 10 cm above the soil level at 1800 h.Absorbent cotton was placed on the top of each decapitated stem andcovered with a polyethylene sheet. To avoid night dews and directsunlight, the stems with absorbent cotton were covered with a paperbag. At 0600 h of the following morning the absorbent cotton with rootbleeding sap was collected and the root bleeding rate was estimatedfrom the increase in cotton weight (Hirasawa et al., 1983).

The method of extraction of cytokinins (Z and ZR) were describedby Pan et al. (2010), with [2H5]-Z, [2H5]-ZR, [2H6]-iP and [2H6]-iPR asinternal standard. Cytokinins were detected by multiple reactionmonitoring (MRM) liquid chromatography-tandem mass spectrometry(LC–MS/MS) (TSQ Vantage, Thermo Fisher Scientific, Waltham, MA,USA) according to the protocols (Pan et al., 2010; Müller and Munné-Bosch, 2011) and was quantified using a calibration curve with knownamounts of standard and based on the ratio of the summed area of theMRM transitions for cytokinins to those for their internal standards.Data acquisition and analysis were performed using Xcalibur DataSystem (Thermo Fisher Scientific, Waltham, MA, USA).

Aboveground plants were separated into straw, filled and unfilledgrains, and rachis. Dry weights of each component were determined byoven drying at 72 °C to constant weight and weighing. Tissue N contentwas determined by micro-Kjeldahl digestion, distillation, and titration

to calculate aboveground N uptake (Yoshida et al., 1976). The methodsfor calculating NUE were according to Ju et al. (2015). IWP were cal-culated using the following formula: IWP (kg grain m−3) = grain yield/the amount of irrigation water.

2.4. Final harvesting

All plants were harvested on 14–16 October. Grain yield was de-termined from all plants from a 5 m2 area (except border plants) in eachplot and adjusted to a moisture content of 0.14 g H2O g−1 fresh weight.Aboveground biomass and yield components, i.e. number of paniclesper square meter, percentage of filled grains and grain weight, weredetermined from 50 plants (excluding the border ones) sampled ran-domly from each plot. The percentage of filled grains was defined as thefilled grains (specific gravity≥ 1.06 g cm−3) as a percentage of totalnumber of spikelets. The number of spikelets per panicle was calculatedfrom the grain yield, grain weight (14% moisture content), and per-centage of filled grains, i.e. number of spikelets per panicle = grainyield per square meter/(number of panicles per square meter × 1000-grain weight × percentage of filled grains).

2.5. Statistical analysis

Analysis of variance was performed using SAS/STAT statisticalanalysis package (version 6.12, SAS Institute, Cary, NC, USA). The plotswere generated using SigmaPlot 10.0 software. Data from each sam-pling date were analyzed separately. Means were tested by least sig-nificant difference at P = 0.05 (LSD0.05). There was no significant dif-ference between years and in the interaction between the year and thetreatment. Therefore the data were presented as the average across thetwo study years.

3. Results

3.1. Tiller number and leaf area index (LAI)

The number of tillers varied with crop managements and mea-surement times (Table 2). Compared to LFP, ICM1 (progressive in-troduction of reduced nitrogen and increased density) increased thenumber of tillers by 2.9%, 10.6% and 10.5% for W24 and 3.2%, 9.1%and 5.6% for Y2640, respectively, at panicle initiation, heading timeand maturity stage. Compared to ICM1, the ICM2 (progressive in-troduction of AWMD) increased the number of tillers by 3.2% and 1.5%for W24 and 4.4% and 6.5% for Y2640 at heading time and maturitystages, respectively. Compared to ICM2, the ICM3 (progressive in-troduction of organic fertilizer as basal fertilizer) increased the numberof tillers by 6.8%, 7.1%, 1.1% and 5.5% for W24 and 2.6%, 6.8%, 1.1%

Table 2Number of tillers and the percentage of productive tillers of the rice cultivars W24 and Y2640 under various treatments.

Cultivar Treatmenta Number of tillers and main stems per m2 Productive tillers (%)b

Mid tillering Panicle initiation Heading stage Maturity stage

W24 0 N 60.1 c c 185 d 171 d 153 d 82.7 aLFP 108 a 324 c 242 c 237 c 73.3 cICM1 104 b 333 b 267 b 262 b 78.6 bICM2 103 b 326 c 276 a 266 b 81.9 abICM3 110 a 349 a 279 a 281 a 80.6 ab

Y2640 0 N 78.2 c 151 c 130 d 121 d 80.5 aLFP 143 a 235 b 166 c 160 c 67.8 dICM1 136 b 243 ab 181 b 169 b 69.6 dICM2 134 b 235 b 189 a 180 a 76.6 bICM3 138 b 251 a 191 a 184 a 73.6 c

a 0 N, LFP, ICM1, ICM2 and ICM3 represent no N application, local farmer’s practice, integrative crop management 1, integrative crop management 2, and integrative crop man-agement 3, respectively.b The number of panicles developed from tillers (tillers at maturity) / the number of tillers at the jointing stage.c Different letters indicate statistical significance atthe P = 0.05 level within the same column and the same cultivar.

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and 2.5% for Y2640, respectively (Table 2). The percentage of pro-ductive tillers was increased by 7.2% for W24 and 2.7% for Y2640under ICM1 than under LFP, and by 4.2% for W24 and 10.0% for Y2640under ICM2 than under ICM1. However, the percentage of productivetillers was decreased by 1.6% for W24 and 3.9% for Y2640 under ICM3than under ICM2 (Table 2).

The LAI was increased from mid tillering, and peaked at headingtime, then declined. The LAI was increased by 4.8%, 19.2%, 20.0% and86.7% for W24 and 3.8%, 13.7%, 14.0% and 93.4% for Y2640 underICM1 than under LFP, by 4.6%, 18.2%, 6.2% and 5.2% for W24 and4.6%, 17.3%, 5.4% and 5.1% for Y2640 under ICM2 than under ICM1,and by 24.0%, 21.5%, 15.8% and 16.5% for W24 and 19.8%, 15.0%,6.7% and 11.7% for Y2640 under ICM3 than under ICM2, respectively,at mid tillering, panicle initiation, heading time and maturity stages.However, the effective LAI rate was decreased by 2.2% for W24 and0.9% for Y2640 under ICM3 than under ICM2 (Table 3).

3.2. Leaf area duration (LAD) and crop growth rate (CGR)

LAD was gradually increased with growth stage (Fig. 2). LADshowed no significant difference from transplanting to mid tilleringamong the five crop managements. Compared to LFP, ICM1 increasedor significantly increased LAD by 22.6%, 15.6% and 9.0% for W24 and22.0%, 11.3% and 6.1% for Y2640 from mid tillering to panicle in-itiation, from panicle initiation to heading time, and from heading timeto maturity, respectively. Compared to ICM1, ICM2 increased or sig-nificantly increased LAD by 7.3%, 3.8% and 2.6% for W24 and 7.7%,5.5% and 4.1% for Y2640, respectively. Compared to ICM2, ICM3 in-creased or significantly increased LAD by 14.4%, 9.7% and 10.0% forW24 and 15.5%, 8.4% and 6.0% for Y2640, respectively (Fig. 2).

CGR showed increases from transplanting to mid tillering, from midtillering to panicle initiation and from panicle initiation to headingtime, and peaked from panicle initiation to heading time, and declinedthereafter (Fig. 3). CGR showed no significant difference among thefour crop managements (LFP, ICM1, ICM2, and ICM3) from trans-planting to mid tillering. CGR was increased by 26.7%, 13.3% and 5.1%for W24 and 14.0%, 9.7% and 11.8% for Y2640 under ICM1 than underLFP, by 4.4%, 8.0% and 4.6% for W24 and 3.5%, 7.3% and 12.1% forY2640 under ICM2 than under ICM1, and by 11.5%, 3.7% and 7.0% forW24 and 5.7%, 5.3% and 12.6% for Y2640 under ICM3 than underICM2, respectively, from mid tillering to panicle initiation, from panicleinitiation to heading time, and from heading time to maturity. CGR forY2640 was higher than for W24 at each growth stage (Fig. 3).

3.3. Root dry weight and length

Seasonal dynamics of root biomass was presented in Fig. 4A and B.The root dry weight for Y2640 was higher than W24 throughout thegrowth season in both years. Compared to LFP, the ICM1 increased orsignificantly increased root dry weight by 34.7%, 5.0%, 3.0% and 0.3%for W24 and 37.1%, 10.2%, 9.8% and 2.9% for Y2640 at mid tillering,panicle initiation, heading time and maturity, respectively. Comparedto ICM1, the ICM2 increased or significantly increased root dry weightby 2.7%, 1.4%, 2.0% and 7.6% for W24 and 4.2%, 0.1%, 1.8% and2.9% for Y2640, respectively. Compared to ICM2, the ICM3 increasedor significantly increased root dry weight by 7.9%, 6.2%, 10.5% and10.6% for W24 and 8.6%, 9.8%, 5.7% and 0.6% for Y2640, respectively(Fig. 4A and B).

Similar to root dry weight, the root length was increased or sig-nificantly increased with the progressive introduction of single

Table 3Leaf area index (LAI) of the rice cultivars W24 and Y2640 at different growth stages under various treatments.

Cultivar Treatmenta Mid tillering Panicle initiation Heading time Maturity

Total Effective leaf area

(LAI) b (%)

W24 0 N 0.57 ec 1.53 e 2.51 e 2.34 e 93.4 a 0.94 dLFP 0.84 d 3.42 d 5.61 d 4.80 d 85.7 d 1.54 cICM1 0.88 c 4.08 c 6.73 c 5.97 c 88.8 c 2.88 bICM2 0.92 b 4.82 b 7.14 b 6.73 b 94.3 a 3.03 bICM3 1.14 a 5.85 a 8.27 a 7.62 a 92.2 b 3.53 a

Y2640 0 N 0.60 c 1.26 e 2.16 e 2.05 e 94.9 a 0.89 dLFP 1.05 b 3.41 d 5.49 d 4.81 d 87.5 c 1.44 cICM1 1.09 b 3.87 c 6.26 c 5.66 c 90.4 b 2.78 bICM2 1.14 b 4.54 b 6.60 b 6.22 b 94.2 a 2.92 bICM3 1.36 a 5.22 a 7.04 a 6.58 a 93.4 a 3.26 a

a 0 N, LFP, ICM1, ICM2 and ICM3 represent no N application, local farmer’s practice, integrative crop management 1, integrative crop management 2, and integrative crop man-agement 3, respectively.

b Effective LAI was defined as the LAI of productive tillers and main stems, and the percentage of effective LAI was defined as the effective LAI as a percentage of total LAI.c Different letters indicate statistical significance at the P = 0.05 level within the same column and the same cultivar.

Fig. 2. Leaf area duration of the rice cultivars W24 (A) andY2640 (B) under various treatments. 0 N, LFP, ICM1, ICM2and ICM3 represent no N application, local farmer’s practice,integrative crop management 1, integrative crop manage-ment 2, and integrative crop management 3, respectively. TR-MT, MT-PI, PI-HT and HT-MA represent the growth stagesfrom transplanting to mid-tillering, from mid-tillering to pa-nicle initiation, from panicle initiation to heading time, andfrom heading time to maturity, respectively. Vertical barsrepresent ± standard error of the mean (n = 6) where theseexceed the size of the symbol.

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cultivation technology from mid tillering to maturity (Fig. 4C and D).

3.4. Leaf photosynthetic rate, root oxidation activity (ROA) and bleeding,and contents of zeatin (Z) and zeatin riboside (ZR) in roots and in leaves

Leaf photosynthetic rate was increased from mid tillering to headingtime, and peaked at heading time, and declined thereafter (Fig. 5).Compared to LFP, the ICM1 increased or significantly increased leafphotosynthetic rate by 7.3%, 12.1%, 3.2% and 11.2% for W24 and8.5%, 7.7%, 2.2% and 4.7% for Y2640 at mid tillering, panicle initia-tion, heading time and maturity, respectively. Compared to ICM1, theICM2 increased or significantly increased leaf photosynthetic rate by8.0%, 1.9%, 3.7% and 1.7% for W24 and 5.6%, 3.4%, 2.5% and 4.0%for Y2640, respectively. Compared to ICM2, the ICM3 increased orsignificantly increased leaf photosynthetic rate by 2.8%, 3.6%, 5.4%and 13.0% for W24 and 6.5%, 5.4%, 3.6% and 6.4% for Y2640, re-spectively (Fig. 5).

Very similar results were observed for ROA and root bleedingthroughout the growth season (Fig. 6). The root activities were in-creased or significantly increased with the progressive introduction ofsingle cultivation technology from mid tillering to maturity. The ROAand root bleeding for Y2640 were higher than that for W24 at eachgrowth stage (Fig. 6).

Z + ZR contents in roots, in per unit root DW basis, differed sig-nificantly with managements and measurement times. The Z + ZRcontents in roots for Y2640 were higher than that for W24 at each

growth phase (Fig. 7A and B). Z + ZR contents in roots were increasedby 6.0%, 4.6%, 13.7% and 15.8% for W24 and 3.6%, 7.2%, 12.0% and14.5% for Y2640 under ICM1 than that under LFP at mid tillering,panicle initiation, heading time and maturity, respectively. Z + ZRcontents in roots were increased by 14.3%, 15.0%, 13.2% and 40.1%for W24 and 5.6%, 8.4%, 10.2% and 18.0% for Y2640 under ICM2 thanthat under ICM1, respectively. Z + ZR contents in roots were increasedby 1.9%, 6.4%, 12.2% and 6.6% for W24 and 7.4%, 8.1%, 10.2% and7.3% for Y2640 under ICM3 than that under ICM2, respectively(Fig. 7A and B). A similar changing pattern was observed for Z + ZRcontents in leaves (Fig. 7C and D). The Z + ZR contents in roots wasmuch high than that in leaves.

3.5. NSC remobilization

The NSC accumulation in the stem at heading and maturity weresignificantly increased with the progressive introduction of single cul-tivation technology (Table 4). The NSC remobilization was increased by13.6% for W24 and 11.9% for Y2640 under ICM1 than under LFP, andby 15.7% for W24 and 10.6% for Y2640 under ICM2 than under ICM1.However, the NSC remobilization was decreased by 20.9% for W24 and18.0% for Y2640 under ICM3 than under ICM2 (Table 4). Similar re-sults were observed for contribution of NSC to the grain. The NSCcontribution to grain was increased by 15.3% for W24 and 3.3% forY2640 under ICM1 than under LFP, and by 34.5% for W24 and 49.7%for Y2640 under ICM2 than under ICM1. However, the NSC

Fig. 3. Crop growth rate of the rice cultivars W24 (A) andY2640 (B) under various treatments. 0 N, LFP, ICM1, ICM2and ICM3 represent no N application, local farmer’s practice,integrative crop management 1, integrative crop manage-ment 2, and integrative crop management 3, respectively. TR-MT, MT-PI, PI-HT and HT-MA represent the growth stagesfrom transplanting to mid-tillering, from mid-tillering to pa-nicle initiation, from panicle initiation to heading time, andfrom heading time to maturity, respectively. Vertical barsrepresent ± standard error of the mean (n = 6) where theseexceed the size of the symbol.

Fig. 4. Root dry weight (A and B) and root length (C and D)of the rice cultivars W24 (A and C) and Y2640 (B and D)under various treatments. 0 N, LFP, ICM1, ICM2 and ICM3represent no N application, local farmer’s practice, in-tegrative crop management 1, integrative crop management2, and integrative crop management 3, respectively. MT, PI,HT and MA represent mid tillering, panicle initiation,heading time and maturity, respectively. Vertical bars re-present ± standard error of the mean (n = 6) where theseexceed the size of the symbol.

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contribution to grain was decreased by 5.1% for W24 and 10.6% forY2640 under ICM3 than under ICM2 (Table 4).

3.6. Grain yield, NUE, IWP and economic benefit analysis

Table 5 shows the yield and yield components of the two varieties.The grain yield was significantly increased with the progressive in-troduction of single cultivation technology (Table 5). Compared to LFP,ICM1 significantly increased grain yield by 9.0% for W24 and 11.3%forY2640. Compared to ICM1, ICM2 significantly increased grain yield by12.8% for W24 and 12.1%for Y2640. Compared to ICM2, ICM3 sig-nificantly increased grain yield by 3.7% for W24 and 6.0%for Y2640. Ahigher grain yield under the three integrative crop managements wasmainly due to a larger sink size (total number of spikelets per m2) as aresult of a larger panicle (more spikelets per panicle). The total numberof spikelets was gradually increased or significantly increased with theprogressive introduction of single cultivation technology. Increases inthe percentage of filled grains and in grain weight also contributed to ahigher grain yield under ICM2 or ICM2 (Table 5).

Similar to grain yield, the nitrogen uptake and NUE were sig-nificantly increased with the progressive introduction of single culti-vation technology (Table 6). Internal nitrogen use efficiency (IEN),agronomic nitrogen use efficiency (AEN), physiological nitrogen useefficiency (PEN), nitrogen partial factor productivity (PFPN), and ap-parent recovery efficiency of nitrogen fertilizer (REN) were increased by3.7%, 43.2%, 16.8%, 21.1% and 22.3% for W24 and 4.8%, 60.0%,

28.2%, 24.0% and 24.9% for Y2640 under ICM1 than under LFP, by10.8%, 34.6%, 30.3%, 13.0% and 3.2% for W24 and 10.6%, 36.7%,32.9%, 13.1% and 2.5% for Y2640 under ICM2 than under ICM1, andby −3.4%, 8.2%, −4.2%, 3.5% and 13.3% for W24 and −6.3%,14.7%, −7.8%, 4.9% and 24.6% for Y2640 under ICM3 than underICM2, respectively (Table 6).

Compared to CF, the AWMD decreased irrigation water input by16.5% for W24 and 15.4%for Y2640 (Fig. 8A). Compared to LFP, ICM1increased IWP (grain yield/the amount of irrigation water) by 9.0% forW24 and 11.3%for Y2640. Compared to ICM1, ICM2 increased IWP by35.2% for W24 and 32.4%for Y2640. Compared to ICM2, ICM3 in-creased IWP by 3.7% for W24 and 6.0%for Y2640 (Fig. 8B).

Table 7 shows the economic benefit analysis of the rice cultivarsunder various treatments (Table 7). The economic benefit was in-creased by 17.3% for W24 and 19.8% for Y2640 under ICM1 than underLFP, by 24.8% for W24 and 25.9% for Y2640 under ICM2 than underICM1, and by 41.7% for W24 and 38.0% for Y2640 under ICM3 thanunder ICM2. Higher production value of Y2640 balanced the cost ofexpensive hybrid seeds (Table 7). There was no significant difference inthe economic benefit under the same treatment between W24 andY2640. Higher cost of organic fertilizer under ICM3 resulted in lowereconomic benefit (Table 7).

4. Discussion

Although the effect of integrated soil-crop system management,

Fig. 5. Leaf photosynthetic rate of the rice cultivars W24 (A)and Y2640 (B) under various treatments. 0 N, LFP, ICM1,ICM2 and ICM3 represent no N application, local farmer’spractice, integrative crop management 1, integrative cropmanagement 2, and integrative crop management 3, respec-tively. MT, PI, HT and MA represent mid tillering, panicleinitiation, heading time and maturity, respectively. Verticalbars represent ± standard error of the mean (n = 20) wherethese exceed the size of the symbol.

Fig. 6. Root oxidation activity (Aand B) and root bleeding (Cand D) of the rice cultivars W24 (A and C) and Y2640 (B andD) under various treatments. 0 N, LFP, ICM1, ICM2 and ICM3represent no N application, local farmer’s practice, in-tegrative crop management 1, integrative crop management2, and integrative crop management 3, respectively. MT, PI,HT and MA represent mid tillering, panicle initiation,heading time and maturity, respectively. Vertical bars re-present ± standard error of the mean (n = 6) where theseexceed the size of the symbol.

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improved crop management, or optimizing nutrition management onrice yield, agronomic performance, NUE or IWP has been studied pre-viously (Yao et al., 2012; Zhang et al., 2012a,b; Xue et al., 2013; Suiet al., 2013; Chen et al., 2014), little information is known about theeffect of progressive integrative crop managements on agronomic andphysiological performance in rice. Our results showed that, whencompared to LFP, the integrative crop managements (ICM1, ICM2 andICM3) could not only increase grain yield, NUE and IWP, but also en-hance agronomic and physiological performances, including greaternumber of tillers at panicle initiation, heading time and maturity stage,and percentage of productive tillers (Table 2), greater LAI throughoutthe growth season and the percentage of effective leaf area at heading(Table 3), greater LAD and CGR from mid tillering to maturity (Fig. 2and 3), larger root dry weight and length (Fig. 4), greater leaf photo-synthetic rate, ROA, root bleeding, and contents of Z+ ZR in roots andin leaves (Figs. 5–7), greater NSC accumulation in the stem at headingand maturity and contribution of NSC to grain (Table 4). These

agronomic and physiological performances were gradually increasedwith the progressive introduce of single cultivation technology.

There is a proposal that an increase in plant density may generallyresult in denser canopy, which is more susceptible to lodging and da-mage from diseases and insects (Venkateswarlu and Visperas, 1987;Mohapatra and Sahu, 1991; Fageria, 2007). However, low plant densitycould cause a small population and low radiation use efficiency, andlead to low grain yield, which is a common problem under the localfarmer’s practice in current rice production in China (Chen et al., 2014;Ju et al., 2015). In our study, the plant density under integrative cropmanagements (ICM1, ICM2 and ICM3) was 31.25 hills m−2, 20%higher than under LFP. LAI at heading time was within a reasonablerange of 6.25–8.31, and the situation of lodging was not observed. Theplant was healthy and without any damage caused by plant diseases,insect pests and weeds under ICM when the control technology of dis-eases, pests and weeds was the same as under LFP. The results suggestthat adoption of the integrative and optimized crop management (keytechnologies including reduced nitrogen and increased density, AWMD,organic fertilizer application) is effective to increase grain yield andresource-use efficiency through improving main agronomic and phy-siological performances that are associated with higher grain yield,NUE and IWP.

Increase yield sink capacity (panicles by spikelets per unit area) isthe premise to realize higher yield (Ma et al., 2004; Xu et al., 2005;Zhang et al., 2013). In general knowledge, large panicle with morespikelets is negatively correlated with percentage of filled grains(Venkateswarlu and Visperas, 1987; Mohapatra and Sahu, 1991;Fageria, 2007). However, in this study, we observed that when com-pared to LFP, ICM2 and ICM3 could not only increase yield sink ca-pacity, but also enhance the percentage of filled grains. Simultaneousincrease in yield sink capacity and percentage of filled grains may beattributed to the improvement in agronomic and physiological perfor-mances, such as a greater percentage of productive tillers, root biomassand length, LAI, LAD, CGR, shoot activity (leaf photosynthetic rate andZ + ZR in leaves) and root activity (ROA, root bleeding and Z + ZR inroots), and more NSC accumulation in stems and remobilization of NSCto the grain during the grain-filling stage under ICM2 and ICM3 (Tables2–4; Fig. 2–7). It is noteworthy that yield increase under ICM3 was only3.7-6.0% compared to ICM2, and much less than the increase from LFPto ICM1 or from ICM1 to ICM2, indicating that the reduction in

Fig. 7. Zeatin (Z) + zeatin riboside (ZR) contents in roots (Aand B) and in leaves (C and D) of the rice cultivars W24 (Aand C) and Y2640 (B and D) under various treatments. 0 N,LFP, ICM1, ICM2 and ICM3 represent no N application, localfarmer’s practice, integrative crop management 1, integrativecrop management 2, and integrative crop management 3,respectively. MT, PI, HT and MA represent mid tillering, pa-nicle initiation, heading time and maturity, respectively.Vertical bars represent ± standard error of the mean (n = 6)where these exceed the size of the symbol.

Table 4Non-structural carbohydrate (NSC) in stems and NSC remobilization during grain fillingof the rice cultivars W24 and Y2640 under various treatments.

Cultivar Treatmenta NSC atheading(t ha−1)

NSC atmaturity(t ha−1)

RemobilizedNSC reserveb

(%)

NSCcontribution tograinc (%)

W24 0 N 1.43 e d 0.62 d 56.9 a 13.2 bLFP 2.07 d 1.28 c 38.5 d 8.80 dICM1 2.30 c 1.30 c 43.8 c 10.2 cICM2 2.99 b 1.48 b 50.6 b 13.7 aICM3 3.81 a 2.29 a 40.0 d 13.0 b

Y2640 0 N 1.59 e 0.63 d 60.7 a 13.5 aLFP 2.34 d 1.45 c 37.9 d 9.20 cICM1 2.40 c 1.38 c 42.4 c 9.51 cICM2 3.62 b 1.92 b 46.9 b 14.2 aICM3 4.20 a 2.59 a 38.5 d 12.7 b

a 0 N, LFP, ICM1, ICM2 and ICM3 represent no N application, local farmer’s practice,integrative crop management 1, integrative crop management 2, and integrative cropmanagement 3, respectively.

b (NSC in stems at heading-NSC in stems at maturity)/NSC in stems at heading × 100.c (NSC in stems at heading-NSC in stems at maturity)/total grain weight × 100.d Different letters indicate statistical significance at the P = 0.05 level within the same

column and the same cultivar.

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nitrogen rate, increase in plant density and adoption of AWMD couldgreatly improve grain yield. However, yield increase is smaller with theprogressive introduce of organic fertilizer application on the basis ofabove three crop management practices.

Approximate 90% of grain yield in rice comes from the photo-synthesis, and about 60–80% of grain yield comes from the product ofphotosynthesis after heading (Zhang et al., 2010a,b; Gu et al., 2012).Therefore, the product of photosynthesis after heading will play animportant role in high or super high yield of rice. The present resultsshowed that when compared with LFP, ICM increased or significantlyincreased leaf photosynthetic rate before and after heading with theprogressive introduce of single cultivation technology. Moreover, ICMalso increased LAI, effective LAI and LAD, suggesting that the increasein grain yield from not only greater leaf photosynthetic rate but alsomore rational composition of canopy structure.

The remobilization of carbon reserves accumulated in stems duringthe vegetative growth period can contribute to the sink strength incereals (Horie et al., 2005; Fu et al., 2011). It is reported that grain-filling rate is closely associated with sink strength (Liang et al., 2001;Yang et al., 2003; Tommaso et al., 2016). The sink strength includedsink size and sink activity. Sink size is a physical restraint, and sink

activity is the physiological constraint upon a sink organ’s assimilateimport (Ho, 1988). It has been proposed that crop growth rate during atwo-week period before heading in rice is closely associated with pre-anthesis non-structural carbohydrate (NSC) reserves in the stem, en-dosperm development, and grain filling of rice (Horie et al., 2005), Thepresent results showed that the amount of NSC accumulation in thestem at heading time and maturity stage was greatly increased with the

Table 5Grain yield, yield components and harvest index of the rice cultivars W24 and Y2640under various treatments.

Cultivar Treatmenta Grainyield(t ha−1)

Paniclesper m2

Spikeletsper panicle

Filledgrains(%)

Grainweight(mg)

W24 0 N 6.18 e b 153 d 174 b 85.4 a 27.1 bLFP 9.03 d 237 c 174 b 80.6 d 27.2 bICM1 9.85 c 262 b 175 b 79.2 e 27.2 bICM2 11.1 b 266 b 182 a 83.8 b 27.4 aICM3 11.5 a 281 a 183 a 82.1 c 27.4 a

Y2640 0 N 7.15 e 121 d 272 c 86.7 a 25.1 bLFP 9.63 d 160 c 303 b 79.8 bc 25.0 bICM1 10.7 c 169 b 322 a 78.9 c 25.1 bICM2 12.0 b 179 a 324 a 81.7 b 25.3 aICM3 12.7 a 184 a 337 a 81.0 bc 25.4 a

a 0 N, LFP, ICM1, ICM2 and ICM3 represent no N application, local farmer’s practice,integrative crop management 1, integrative crop management 2, and integrative cropmanagement 3, respectively.

b Different letters indicate statistical significance at the P= 0.05 level within the samecolumn and the same cultivar.

Table 6Nitrogen content and uptake at maturity, N use efficiency of the rice cultivars W24 and Y2640 under various treatments.

Cultivar Treatmenta N rate (kg N ha−1) N uptake (kg N ha−1) IENb (kg grainkg−1 N)

AENc (kg grainkg−1 N)

PENd (kg grainkg−1 N)

PFPNe (kg grainkg−1 N)

RENf (%)

W24 0 N 0 81.0 eg 76.0 a – – – –LFP 300 170 d 53.1 d 9.50 d 32.1 d 30.1 d 29.6 dICM1 270 179 c 55.0 cd 13.6 c 37.5 c 36.5 c 36.2 cICM2 270 182 b 61.0 b 18.3 b 48.9 a 41.2 b 37.4 bICM3 270 196 a 58.9 bc 19.8 a 46.8 b 42.7 a 42.3 a

Y2640 0 N 0 88.0 e 81.3 a – – – –LFP 300 175 d 55.1 d 8.30 d 28.6 d 32.1 d 29.0 cICM1 270 186 c 57.8 cd 13.2 c 36.6 c 39.8 c 36.2 bICM2 270 188 b 63.9 b 18.1 b 48.7 a 45.0 b 37.1 bICM3 270 213 a 59.9 bc 20.7 a 44.9 b 47.2 a 46.2 a

a 0 N, LFP, ICM1, ICM2 and ICM3 represent no N application, local farmer’s practice, integrative crop management 1, integrative crop management 2, and integrative crop man-agement 3, respectively.

b IEN, internal nitrogen use efficiency: grain yield (kg)/N uptake of plants (kg).c AEN, agronomic nitrogen use efficiency: [grain yield in N application plots- grain yield in N omission plots (kg)]/N rate (kg).d PEN, physiological nitrogen use efficiency: [grain yield in N application plots- grain yield in N omission plots (kg)]/[N uptake in N application plots- N uptake in N omission plots

(kg)].e PFPN, nitrogen partial factor productivity: grain yield (kg)/N rate (kg).f REN, apparent recovery efficiency of nitrogen fertilizer: [N uptake in N application plots- N uptake in N omission plots (kg)]/N rate (kg) × 100.g Different letters indicate statistical significance at the P = 0.05 level within the same column and the same cultivar.

Fig. 8. Irrigation water input (A) and productivity (B) of the rice cultivars W24 andY2640 under various treatments. 0 N, LFP, ICM1, ICM2 and ICM3 represent no N ap-plication, local farmer’s practice, integrative crop management 1, integrative crop man-agement 2, and integrative crop management 3, respectively. Vertical bars represent ±standard error of the mean (n = 6) where these exceed the size of the symbol.

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progressive introduce of single cultivation technology. Moreover, theNSC remobilization and contribution to grain were greatly enhanced bythe all ICM treatments (Table 4), which may result in a higher per-centage of filled grains, and consequently a higher grain yield, NUE andIWP.

It was reported that leaf photosynthetic characteristics were closelycorrelated with and root physiological activity, and there was an in-terdependent relationship between shoot and root (Ju et al., 2015;Wang et al., 2016). Actively photosynthesizing shoots that ensure asufficient assimilates supply to roots can develop and maintain activeroot function. Conversely, high root activity secures a high photo-synthetic rate by supplying a sufficient amount of nutrients, water andhormones to the shoot. Improvement in root growth and root-shootinteraction is vitally important to achieve a higher yield in crops (Osakiet al., 1997; Samejima et al., 2004; Yang et al., 2004). Chu et al. (2013)pointed out that the improved root morphology and physiology canbenefit shoot physiological processes. Our previous work demonstratedthat the increase in cytokinin (Z + ZR) levels in the shoot and rootcould contribute to a greater grain-filling rate and a heavier grainweight (Zhang et al., 2009a,b,c, 2010a,b). We observed herein thatwhen compared with LFP, ICM increased or significantly increased leafphotosynthetic rate, ROA and root bleeding and Z + ZR content inroots and leaves, and these shoot and root activity parameters wereincreased or significantly increased with the progressive introduction ofsingle cultivation management technology throughout the growthseason (Figs. 5–7), indicating that greater shoot and root physiologicalactivity are important physiological basis for achieving a higher grainyield, NUE and IWP under the ICM treatments. However, further re-search is needed to understand the mechanism in which root-shootinteracts for higher grain yield and higher resource use efficiency.

How could the ICM treatments improve agronomic and physiolo-gical performances and increase grain yield and resource use effi-ciency? In this study, key techniques that are associated with high grainyield, NUE and IWP under ICM treatments were the following: (i) in-creasing plant density. When compared with that under LFP, the plantdensity was increased by 20% under ICM. Increasing plant densitycould reduce the amount of N applied during the early growing seasonwhile achieving enough panicle number per unit area for maximumgrain yield, and consequently reducing N losses and increasing grainyield and NUE (Tables 2–6), (ii) reducing N application and applying Nat later growth stage. When compared with those under LFP, total Nwas decreased by 10% and more proportion of N was applied at latergrowth stages under ICM, which could reduce unproductive tillers, in-crease the productive tiller rate, and promote plant growth at middle-late stages, improve dry matter production after flowering, and conse-quently, increase NUE (Tables 2–6; Fig. 2 and 3), (iii) adoption of al-ternate wetting and moderate drying (AWMD). AWMD could enhanceshoot and root growth, which could benefit physiological processes andresult in a higher grain yield and IWP under both ICM2 and ICM3

(Tables 2–5; Figs. 2–8), and (iv) applying rapeseed cake fertilizer. Theorganic fertilizer supplemented the amount of organic matter N,phosphorus and potassium in soil, and played a role as slow-releasedfertilizer. However, expensive organic fertilizer also increased produc-tion cost.

5. Conclusion

The integrative and optimized crop management (key techniques,i.e., increasing density, reducing N application and applying N at latergrowth stage, alternate wetting and moderate soil drying, applyingrapeseed cake fertilizer) could achieve the dual goal of increasing grainyield and resource use efficiency through improving the agronomic andphysiological performances that are associated with a higher grainyield, NUE and IWP. Higher grain yield, NUE and IWP under the in-tegrative and optimized crop management were attributed to sub-stantially increased sink size, percentage of productive tillers, LAI, LAD,CGR, NSC accumulation and remobilization, leaf photosynthetic rate,root dry weight and length, ROA, root bleeding, and Z + ZR content inroots and leaves. The mechanism underlying root-shoot interaction forhigh grain yield and high resource use efficiency merits further in-vestigation.

Acknowledgements

Thanks to Dr. Thomas R. Sinclair (North Carolina State University)for suggestions and kindly polishing the manuscript. This work wassupported by the National Basic Research Program (2015CB150404),the National Key Research and Development Program(2016YFD0300206-4), the National Natural Science Foundation ofChina (31201155, 31471438, 31461143015), the Natural ScienceFoundation of the Jiangsu Higher Education Institutions(15KJA210005), Young Elite Scientists Sponsorship Program by CAST(2016QNRC001), the Project Funded by the Priority Academic ProgramDevelopment of Jiangsu Higher Education Institutions, and the TopTalent Support Plan of Yangzhou University.

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