Enr

YXa

b

c

a

ARRA

KTDWTWC

1

t

twwprl

(l(

h1

Europ. J. Agronomy 81 (2016) 37–45

Contents lists available at ScienceDirect

European Journal of Agronomy

j ourna l h o mepage: www.elsev ier .com/ locate /e ja

ffects of different soil conservation tillage approaches on soilutrients, water use and wheat-maize yield in rainfed dry-landegions of North China

unhui Shao a,b, Yingxin Xie a,∗, Chenyang Wang a,∗, Junqin Yue b, Yuqing Yao c,iangdong Li b, Weixing Liu a, Yunji Zhu a, Tiancai Guo a

State Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Zhengzhou, 450002, ChinaWheat Research Center of Henan Academy of Agricultural Sciences, Zhengzhou, 450002, ChinaLuoyang Academy of Agriculture and Forestry Sciences, Luoyang, 471024, China

r t i c l e i n f o

rticle history:eceived 4 February 2016eceived in revised form 3 August 2016ccepted 28 August 2016

eywords:illage approachry-land plantingheat and maize rotation system

opsoil nutrientsater use efficiency

rop production

a b s t r a c t

Excessive tillage compromises soil quality by causing severe water shortages that can lead to crop failure.Reports on the effects of conservation tillage on major soil nutrients, water use efficiency and gain yieldin wheat (Triticum aestivum L.) and maize (Zea mays L.) in rainfed regions in the North China Plain arerelatively scarce. In this work, four tillage approaches were tested from 2004 to 2012 in a randomizedstudy performed in triplicate: one conventional tillage and three conservation tillage experiments withstraw mulching (no tillage during wheat and maize seasons, subsoiling during the maize season but notillage during the wheat season, and ridge planting during both wheat and maize seasons). Comparedwith conventional tillage, by 2012, eight years of conservation tillage treatments (no tillage, subsoilingand ridge planting) resulted in a significant increase in available phosphorus in topsoil (0–0.20 m), by3.8%, 37.8% and 36.9%, respectively. Soil available potassium was also increased following conservationtillage, by 13.6%, 37.5% and 25.0%, and soil organic matter by 0.17%, 5.65% and 4.77%, while soil totalnitrogen was altered by −2.33%, 4.21% and 1.74%, respectively. Meanwhile, all three conservation tillageapproaches increased water use efficiency, by 19.1–28.4% (average 24.6%), 10.1–23.8% (average 15.9%)

and 11.2–20.7% (average 15.7%) in wheat, maize and annual, respectively. Additionally, wheat yield wasincreased by 7.9–12.0% (average 10.3%), maize yield by 13.4–24.6% (average 17.4%) and rotation annualyield by 12.3–16.9% (average 14.1%). Overall, our findings demonstrate that subsoiling and ridge plantingwith straw mulching performed better than conventional tillage for enhancing major soil nutrients andimproving grain yield and water use efficiency in rainfed regions in the North China Plain.

. Introduction

Water shortage has become an urgent global problem thathreatens the development of sustainable agriculture and long-

Abbreviations: NCP, North China Plain; WUE, water use efficiency; CT, conven-ional tillage; NTSM, no tillage during wheat and maize seasons and direct drillingith straw mulching; SSM, subsoiling in the maize season but no tillage during theheat season with straw mulching during the wheat and maize season; RSM, ridge

lanting during both wheat and maize seasons wheat and maize sowed on artificialidges ridging before first sowing of wheat and ridge height repaired only in theater growing period; ET, evapotranspiration; N, nitrogen; OM, organic matter.∗ Corresponding authors.

E-mail addresses: shao2937@126.com (Y. Shao), xieyingxin@tom.comY. Xie), xmzxwang@163.com (C. Wang), yjunqin200@126.com (J. Yue),yyaoyuqing@126.com (Y. Yao), hnlxd@126.com (X. Li), wxliu2012@163.comW. Liu), hnndzyj@126.com (Y. Zhu), gtcxiaomai@163.com (T. Guo).

ttp://dx.doi.org/10.1016/j.eja.2016.08.014161-0301/© 2016 Published by Elsevier B.V.

© 2016 Published by Elsevier B.V.

term food security (Islam et al., 2011). China is one of the world’smost water-deficient countries, which has a large region of dry landin the north that accounts for ∼56% of the nation’s total land areabut only 24% of water resources (Wang et al., 2007; Islam et al.,2011). The North China Plain (NCP) is subjected to highly intensiveagriculture and is among the major grain-producing areas. Win-ter wheat (Triticum aestivum L.) and summer maize (Zea mays L.)are two of the most important grain crops grown in this region.In 2014, the NCP produced 70.6% of the nation’s wheat and 54.8%of all maize (China Statistical Book in 2015). Water shortage isparticularly severe in the western rainfed region of the NCP, andunderground water resources are depleting rapidly (Wang et al.,2007; Zhang et al., 2010; Zhang et al., 2013).

Several studies have indicated that changes in tillage approachescan influence agro-environmental processes by altering the waterand nutrient content of soils (Turner, 1989). Appropriate conserva-tion tillage improves soil structure, increases resistance to stresses

3 Agron

ssswe2oiBr2mb

cmrdsii2

arwtaasptTispdsc

iofiTdty

tmaar

2

2

2(sltp

8 Y. Shao et al. / Europ. J.

uch as high temperatures and drought, and reduces water con-umption, all of which increase water use efficiency and minimizeoil erosion (Sisti et al., 2004). Mulching is performed worldwide,hich decreases soil compaction caused by rainfall and reduces

rosion by absorbing the kinetic energy of raindrops (Nyssen et al.,008). Studies showed that mulching significantly reduced evap-ration which increased soil water content and storage, resulting

n improved crop yield and water use efficiency (WUE) (Lentz andjorneberg, 2003). Mulching also effectively conserves water byeducing surface runoff and increasing infiltration (Wang et al.,009). Greater availability of soil water has been attributed toulching with stubble and crop residues that reduce water loss

y evaporation (Munawar et al., 1990).A review by Bossio et al. (2010) highlighted the benefits of

onservation agriculture that combine non-inversion tillage (mini-um or zero tillage in place of ploughing) with mulching and crop

otation to reduce evaporation, runoff, erosion and land degra-ation. Other studies found that minimum tillage coupled withtraw mulching was highly effective at decreasing soil temperature,ncreasing soil water content and increasing crop yield by provid-ng maximum surface cover (Bhatt and Khera, 2006; Wang et al.,007).

Similarly, Fuentes et al. (2003) reported that a no tillagepproach helped to conserve soil water in an annual croppingegion in the eastern Washington area by limiting evaporativeater losses and reducing surface runoff. Chu et al. (2010) found

hat strip rotary tillage after subsoiling proved to be the bestpproach for high-yielding wheat production by improving WUEnd enhancing absorption of soil water during the grain-fillingtage. Greater leaching due to higher soil water content and theresence of preferential flow pathways under no tillage may con-ribute to decreased nitrogen availability (Shipitalo et al., 2000).illage approaches also affect soil quality, but the results are var-

ed. Some studies have reported that no tillage or minimum tillageignificantly increases the concentration of OM and nitrogen, com-ared with CT (Shipitalo et al., 2000). However, Wright et al. (2005)etermined that OM and soil organic nitrogen were lower in top-oil under no tillage in maize and cotton (Gossypium hirsutum L.)ropping systems after 20 years of management.

To date, most studies have focused on irrigated fields in var-ous high yielding farming areas, but relatively little is knownn the effects of long-term conservation tillage in non-irrigatedelds operating a wheat-maize rotation system in northern China.here is an urgent need to improve soil water storage capacity byeveloping conservation tillage approaches and crop cultivationechnologies in wheat and maize rotation systems to improve cropield and WUE.

We hypothesize that different tillage approaches will vary inheir ability to enhance soil fertility, WUE and production of wheat,

aize and annual. To test this, the long-term impacts of four tillagepproaches on soil nutrients, WUE and grain yield were tested in

wheat and maize rotation system in a rainfed dry-land farmingegion of northern China.

. Materials and methods

.1. Experimental site

Experiments were performed from October 2004 to September012 in the Luoyang Academy of Agriculture and Forestry Sciences112◦39′E, 34◦62′N), which is located in the semi-arid region at the

outheast edge of China’s Loess Plateau, part of the rainfed dry-and farming area of northern China. This region is in a northernemperate continental monsoon climate zone with mean air tem-erature of 14.5 ◦C from 1991 to 2013 (data sourced from http://

omy 81 (2016) 37–45

data.cma.cn). Rotation planting of winter wheat-summer maizeis the main cropping system employed in this region. The meandrought frequency was >40%, the aridity index was >1.3, and thefrost-free period was 200–219 days per year. The soil in this regionis classified as a Semi-Alfisol derived from yellow brown earthycinnamon soils exhibiting weak leaching during decalcification.Texture and other properties of the topsoil (0–0.20 m) are shownin Table 1. Field capacity, saturated water content (gravimetricthroughout this paper) and bulk density in the topsoil (0–0.20 m)were 270 g kg−1, 330 g kg−1 and 1.53 t m−3, respectively.

2.2. Experimental design and management

Each wheat-maize rotation system was studied under field con-ditions from 2004 to 2012. A randomized complete block designwas used for all four tillage approaches, and experiments were per-formed in triplicate. Data (except for soil nutrients) were obtainedfrom 2008 to 2012. The three conservation tillage treatmentsand one conventional tillage approach were performed as follows(Fig. 1):

Conventional tillage (CT): deep ploughing (0.20–0.25 m) andhand sowing for wheat but no tillage sowing for maize, and no strawmulching during wheat and maize seasons (Fig. 1a). Three conser-vation tillage approaches with straw mulching: no tillage duringwheat and maize seasons, and direct drilling with straw mulching(NTSM, Fig. 1b); subsoiling (0.35–0.40 m) by hand during the maizeseason, but no tillage during the wheat season, and straw mulchingduring the wheat and maize seasons (SSM, Fig. 1c); ridge plantingduring both wheat and maize seasons, wheat and maize sowed onartificial ridges (height 0.20 m, width 1.0 m), ridging before firstsowing of wheat in October of 2004, and ridge height repaired onlyin the later stages of the growing period (RSM, Fig. 1d).

In each growing season, wheat was sowed from 8 to 19 Octoberand harvested during 29–31 May. Maize was sowed in earlyJune (2–4 days after wheat harvest), and harvested from 15 to30 September. Each experimental plot covered an area of 16 m2

(4 m × 4 m) and was isolated by a concrete wall (0.20 m aboveground, 0.80 m below ground, 0.15 m wide, Fig. 1).

In each plot treatment, wheat seeds were sowed in 16 rows(Fig. 1) with a seedling density of 270 × 104 per hectare, and maizeseedlings were planted in six rows with a row spacing of 0.60 mand a density of 6.0 × 104 per hectare (96 plant per plot of 16 m2).

Given that most local farmers prioritize wheatproduction over corn yield, compound fertilizer(N–P2O5–K2O = 150 − 150 − 150 g kg−1) was applied at a rateof 600 kg ha−1, and urea (N 460 g kg−1) was supplied at 150 kg ha−1

as basal fertilizer for winter wheat, but only 300 kg ha−1 urea wasapplied for summer maize during the jointing stage, consistentwith local practices.

2.3. Experimental methods

2.3.1. Grain yield and yield componentsPrior to harvest of winter wheat or summer maize from 2008

to 2012, the number of spikes per unit area were determined foreach treatment. At maturity, 20 maize and 80 wheat plants werecollected for determination of kernel number per spike and ker-nel mass. For the determination of grain yield, all plants (16 m2) ineach treatment were hand-harvested and threshed using a station-ary thresher. Grain samples were air-dried prior to weighing, andadjusted to a water content of 0.13 g H2O g−1 fresh weight.

2.3.2. Soil sampling and analysisAt harvest of summer maize in 2004, 2008, 2010 and 2012,

composite soil samples were collected for each treatment usinga ten-point sampling mode at 0.10 m intervals in the 0–0.20 m top-

Y. Shao et al. / Europ. J. Agronomy 81 (2016) 37–45 39

Table 1Physical and chemical characteristics of topsoil (0–0.20 m) at the beginning of the experiment in 2004.

Sand (%) Slit (%) Clay (%) OM (g kg−1) Total N (g kg−1) Available P (mg kg−1) Available K (mg kg−1) CEC (cmol kg−1) pH (1:1 soil and water)

30.2 41.6 28.2 15.8 0.95 3.58 138.3 19.9 7.3

Fig. 1. Photos of the four tillage approaches used in this study. CT: conventional tillage without straw mulching; NTSM: no tillage with straw mulching during the wheat andm t seasod idgingt all fig

shtsFwaTsbd11c

2

oiwt(u

E

W

wd(so

aize seasons; SSM: subsoiling in the maize season but no tillage during the wheauring the wheat and maize seasons, wheat and maize sowed on artificial ridges, rhe later growth period. The abbreviations CT, NTSM, SSM and RSM are the same in

oil layer. Half of these soil samples were collected from rows, andalf between rows, and the ten random subsamples were pooledogether and air-dried prior to nutrient analysis. The OM was mea-ured by the K2Cr2O7-H2SO4 oxidation method (Page et al., 1982).or determination of total P and total K, soil samples were mixedith sodium hydroxide (NaOH), fused in an electric muffle furnace

t 720 ◦C for 15 min and dissolved in sulfuric acid prior to testing.otal K was then determined using an AA800 atomic absorptionpectrophotometer (PerkinElmer, USA) and total P was determinedy molybdenum blue colorimetry. Available P and available K wereetermined by the sodium bicarbonate extraction method (Olsen,954) and the ammonium acetate extraction method (Westerman,990), respectively. All determinations were carried out in tripli-ate.

.3.3. Crop evapotranspiration (ET) and WUESoil samples were collected at 0.20 m intervals at a depth range

f 0–2 m using a soil auger (30 mm diameter) during the main grow-ng stages and at harvest of wheat and maize to determine soil

ater storage and water content. WUE (kg m−3) was calculated ashe crop yield (Y, kg ha−1) divided by the total evapotranspirationET, mm) during the entire growing seasons as described previouslysing the following formulae (Lenka et al., 2009):

T = P + I + �W − R – D + CR (1)

UE = Y/ET (2)

here ET (evapotranspiration) is the total water use during a

efined growing period (mm), P = precipitation (mm), I = irrigationmm), �W = soil water content at the start (usually before cropowing) minus that at the end (usually at crop harvest) at a depthf 2 m (expressed in mm), R = runoff (mm), D = drainage from the

n, and straw mulching during the wheat and maize season; RSM: straw mulching before first sowing of wheat in October of 2004, and ridge height repaired only inures and tables.

root zone and capillary rise (mm), and CR = capillary rise to the rootzone (mm). Runoff, water drainage and irrigation events did notoccur during the experiment, and the capillary rise was negligiblebecause the groundwater table is more than 120 m below the soilsurface in this rainfed region. Thus, ET = P + �W was used for theseexperimental conditions.

2.4. Data analysis

Experimental data were analyzed and tabulated using MicrosoftOffice 2010. SPSS 18.0 was used for statistical analysis. Datafor ET, WUE, crop yield and components were correlated withtillage approach and year, and are therefore presented separately.One-way analysis of variance (ANOVA) was performed to assesssignificant differences between different treatments. Means werecalculated using the LSD test at the 5% probability level.

3. Results

3.1. Effects of conservation tillage on topsoil nutrients

Tillage type clearly affected the availability of nutrients intopsoil in the wheat-maize rotation system, and conservationtillage helped to improve available P and available K in top-soil (Fig. 2). From 2004 (the beginning of the experiment) to2012, all three conservation tillage treatments (NTSM, SSM andRSM) increased available P in topsoil, by 47.7% (from 3.58 mg kg−1

to 5.29 mg kg−1), 95.8% (from 3.58 mg kg−1 to 7.02 mg kg−1) and94.7% (from 3.58 mg kg−1 to 6.97 mg kg−1), respectively. Mean-while, available K was increased by 27.5% (from 138.3 mg kg−1 to176.4 mg kg−1), 54.2% (from 138.3 mg kg−1 to 213.3 mg kg−1) and

40 Y. Shao et al. / Europ. J. Agronomy 81 (2016) 37–45

14.5

15.0

15.5

16.0

16.5

17.0

17.5

OM

con

tent

(g k

g-1)

a

0.80

0.90

1.00

1.10

Tot

al N

con

tent

(g k

g-1)b

0.80

0.85

0.90

0.95

1.00

Tot

al P

con

tent

( P

g kg

-1)

c

10.0

10.5

11.0

11.5

Tot

al K

con

tent

(K g

kg-1

)

d

3.00

4.00

5.00

6.00

7.00

8.00

9.00

2004 2008 2010 2012

Ava

ilabl

e P

cont

ent (

P m

g kg

-1)

Measuring yea r

e

CT NTSM SSM RSM

100

150

200

250

2004 2008 2010 2012

Tot

al K

con

tent

(K g

kg-1

)f

Fig. 2. Soil nutrient properties in the 0–0.20 m topsoil layer at the start (2004),mr

4ta

iatem−i2

3

3

fw(iohmasaiRf

and

grai

n

yiel

d

in

the

fou

r

till

age

pra

ctic

es

in

the

wh

eat-

mai

ze

rota

tion

syst

em

du

rin

g

2008

–201

2.

nts

Mea

n

WU

E

valu

es

du

rin

g

2008

–201

2

Mea

n

grai

n

yiel

d

du

rin

g

2008

–201

2

Wh

eat

(Tri

ticu

m

aest

ivum

L.)

Mai

ze

(Zea

may

s

L.)

An

nu

al

of

wh

eat

and

mai

ze

Wh

eat

(Tri

ticu

m

aest

ivum

L.)

Mai

ze

(Zea

may

s

L.)

An

nu

al

of

wh

eat

and

mai

ze

WU

E(k

g

m−3

)In

crea

sin

gra

te(%

)W

UE

(kg

m−3

)In

crea

sin

gra

te(%

)W

UE

(kg

m−3

)In

crea

sin

gra

te(%

)Y

ield

(kg

ha−1

)In

crea

sin

gra

te(%

)Y

ield

(kg

ha−1

)In

crea

sin

gra

te(%

)Y

ield

(kg

ha−1

)In

crea

sin

gra

te(%

)

2.10

d

–

1.75

c

–

1.80

d

–

4733

c

–

5495

c

–

1022

8

c

–2.

50

c

19.1

1.93

b

10.1

2.01

c

11.2

5251

a

10.9

6234

b

13.4

1148

4

b

12.3

2.66

b

26.4

1.99

b

13.8

2.07

b 15

.1

5300

a

12.0

6281

b

14.3

1158

1

b

13.2

2.70

a

28.4

2.17

a

23.8

2.18

a 20

.7

5108

b

7.9

6849

a

24.6

1195

7

a

16.9

n-

on )

2.62

24.6

2.03

15.9

2.09

15.7

5220

10.3

6455

17.4

1167

4

14.1

hin

a

colu

mn

foll

owed

by

dif

fere

nt

litt

le

lett

ers

are

sign

ifica

ntl

y

dif

fere

nt

at

P

<

5%.

iddle (2008, 2010) and end (2012) of the experiment treatments. The vertical barsepresent LSD0.05.

0.2% (from 138.3 mg kg−1 to 193.9 mg kg−1), respectively. In con-rast, for OM, total N, P and K were altered only slightly in topsoilfter the 8-year conservation tillage treatment (Fig. 2a–d).

Compared with CT, by 2012, NTSM, SSM and RSM treatmentsncreased available P by 3.8%, 37.8% and 36.9%, and increased avail-ble K by 13.6%, 37.5% and 25.0%, respectively (Fig. 2e–f). However,hese treatments had less impact on other nutrients in topsoil. Forxample, compared with CT, by 2012, NTSM, SSM and RSM treat-ents increased OM by 0.17%, 5.65% and 4.77%, and total N by2.33%, 4.21% and 1.74%, respectively (Fig. 2a–b), and also slighted

ncreased total P by 0.58%, 3.62% and 1.64%, and total K by −0.65%,.89% and 2.27%, respectively (Fig. 2c–d).

.2. ET and WUE

.2.1. Wheat growing seasonDuring the winter wheat growing season (from October to the

ollowing May, Fig. 3), precipitation ranged from 76.0 to 250.9 mm,hile water consumption (ET) varied from 97.0 to 523.0 mm

Fig. 4). Maximum ET (513 mm across all treatments) was recordedn the 2011–2012 growing season, whereas minimum ET (97 mm)ccurred in the 2010–2011 growing season, which resulted in theighest and the lowest wheat yields in the corresponding treat-ents (Fig. 4, Table 2). Significant differences in ET and WUE were

pparent among the four tillage treatments across different sea-ons. Compared with CT, the three conservation tillage (NTSM, SSMnd RSM) treatments decreased ET by 19.2%, 26.5% and 28.5%, and

ncreased WUE by 19.1%, 26.4% and 28.4%, respectively, and theSM treatment was associated with the lowest ET in three out of

our wheat seasons (Fig. 4, Table 2). Tab

le

2M

ean

WU

E

Trea

tme

CT

NTS

M

SSM

RSM

Mea

n

(co

serv

ati

till

age

Mea

ns

wit

Y. Shao et al. / Europ. J. Agronomy 81 (2016) 37–45 41

Fig. 3. Monthly precipitation distribution at the experimental site. Bars indicate monthly rainfall during the four planting years 2008–2009, 2009–2010, 2010–2011 and2011–2012. The wheat season was from October (O) to May (M), and the maize season from June (J) to September (S). The continuous dotted line indicates the averagemonthly rainfall during 1991–2013 (data sourced from http://data.cma.cn).

abcd

aababb

aaaa

aaaa

0

100

200

300

400

500

600

700

0100200300400500600700800

Prec

ipita

tion

(mm

)

ET

(mm

)

Wheat

aabbcc

aaab

aaaa

aaaa

0

100

200

300

400

500

600

700

0100200300400500600700800

Prec

ipita

tion

(mm

)

ET

(mm

)

Maize

aaaa

aaab

abbb

aaaa

0

100

200

300

400

500

600

700

0

100

200

300

400

500

600

700

800

2008 -2009 2009 -2010 2010 -2011 2011 -2012Crop grow ing seasons

Prec

ipita

tion

(mm

)

ET

(mm

)

Wheat&maize

Precip CT NT SM SSM RSM

aabc

aabbc a

abc

aaab

0

100

200

300

400

500

600

700

0.0

1.0

2.0

3.0

4.0

Prec

ipita

tion

(mm

)

WU

E ((

kg m

-3)

Wheat

ababab

abbc

aabc

abcd

0

100

200

300

400

500

600

700

0.0

1.0

2.0

3.0

4.0

Prec

ipita

tion

(mm

)

WU

E ((

kg m

-3)

Maize

abbc

abbc

aabc

abbc

0

100

200

300

400

500

600

700

0.0

1.0

2.0

3.0

4.0

2008-2009 2009 -2010 2010-2011 2011-2012

Prec

ipita

tion

(mm

)

WU

E ((

kg m

-3)

Wheat&maize

Fig. 4. Annual precipitation, evapotranspiration (ET) and water use efficiency (WUE) in the four tillage treatments of the wheat-maize rotation system in four successiveyears. Different lowercase letters in the four tillage approaches in the same crop growing season indicate significant differences at the P < 5% level.

4 Agron

3

Svtw2wr2ti1

3

wbfm2vtot(s(hS1ag

3

p(bsA(w(tyigar

ialCC(a1hait

2 Y. Shao et al. / Europ. J.

.2.2. Maize growing seasonDuring the summer maize growing season (from June to

eptember), precipitation ranged from 237.0 to 568.9 mm, and ETaried from 206.0 to 551.0 mm, which accounted for 51–88% ofotal annual precipitation (Figs. 3 and 4). Similarly to wheat, ETas highest in 2008–2009, lower in 2010–2011, higher again in

009–2010 and lowest of all in 2011–2012. Higher values of WUEere obtained in 2009–2010 and 2011–2012, both of which expe-

ienced less precipitation, while WUE was lower in the wetter008–2009 and 2010–2011 seasons. The three conservation tillagereatments (NTSM, SSM and RSM) achieved higher WUE values dur-ng 2009–2012 compared with CT, and increased WUE by 10.1%,3.8% and 23.8%, respectively (Fig. 4, Table 2).

.2.3. Annual changes of wheat and maizeLower annual values of ET (averaged across the four treatments)

ere recorded in 2010–2011 (433 mm) and 2009–2010 (485 mm),ut the highest WUE (2.93 kg m−3) was achieved in 2009–2010,ollowed by 2010–2011 (1.84 kg m−3). Meanwhile, higher annual

ean values of ET were observed in 2011–2012 (722 mm) and008–2009 (686 mm), and these seasons produced lower WUEalues of 1.60 kg m−3 and 1.69 kg m−3, respectively. Specifically,he extremely uneven rainfall distribution in 2010–2011, withnly 76.0 mm in the winter wheat season but 568.9 mm inhe summer maize season, lead to the lowest annual yield7961 kg ha−1). (Figs. 3 and 4, Table 3). Compared with CT, con-ervation tillage treatments increased annual WUE by 15.7%11.2–20.7%) during 2008–2012. Among treatments, RSM gave theighest WUE (2.18 kg m−3) in three of the four years, followed bySM (2.07 kg m−3), and NTSM (2.01 kg m−3), compared with only.80 kg m−3 for CT (Table 2). Therefore, a combination of appropri-te rainfall distribution and optimum tillage approach can increaserain production and WUE significantly in the NCP region.

.3. Winter wheat and summer maize grain yield

Crop yield was closely correlated not only with the amount ofrecipitation, but also with rainfall distribution in this rainfed areaFigs. 3 and 4, and Table 3). Variance analysis also showed thatoth tillage approach and year, and the interaction between them,ignificantly affected crop yield and yield components (Table 3).mong wheat seasons, the highest average yield of 6951 kg ha−1

averaged across the four treatments) was obtained in 2011–2012,hich recorded 229.3 mm of precipitation, followed by 2009–2010

5773 kg ha−1) and 2008–2009 (5235 kg ha−1) in which precipita-ion was 185.9 mm and 250.9 mm, respectively. The lowest averageield (2431 kg ha−1) was obtained in 2010–2011, in which precip-tation was only 76.0 mm (Table 3, Fig. 4). Compared with CT, SSMave the highest average yield (5300 kg ha−1), followed by NTSMnd RSM, which increased the average yield by 12.0, 10.9 and 7.9%,espectively (Table 2).

Unlike wheat, the highest average yield for maize was obtainedn 2009–2010, followed by 2008–2009, 2010–2011 and 2011–2012,nd the lowest precipitation (237.0 mm) was correlated with theowest maize yield (4587 kg ha−1) in 2011–2012 (Table 3, Fig. 4).onservation tillage treatments significantly increased maize yield.ompared with CT, RSM gave the highest average maize yield6849 kg ha−1) of all treatments, in 2008–2012, followed by SSMnd NTSM, which increased the average yield by 24.6%, 14.3% and3.4%, respectively (Table 2). The RSM treatment also gave the

ighest average annual yield of wheat and maize (11957 kg ha−1,veraged across the four years), followed by SSM and NTSM, whichncreased average annual yield by 16.9%, 13.2% and 12.3%, respec-ively (Table 2).

omy 81 (2016) 37–45

3.4. Relationship between rainfall, ET, yield and WUE

Correlation analysis (Table 4) revealed a strong positive cor-relation between rainfall and ET in wheat seasons (r = 0.555**, **represents significance at P < 0.01) and maize seasons (r = 0.293*,* represents significance at P < 0.05). However, a significant neg-ative correlation was observed between ET and WUE in wheatseasons (r = −0.781**), maize seasons (r = −0.658**) and rotationannuals (r = −0.566**), suggesting higher rainfall increased ET, andthe higher ET resulted in lower WUE. Furthermore, a markedlypositive correlation was identified between ET and grain yield inwheat seasons (r = 0.769**), maize seasons (r = 0.307*) and in rota-tion annuals (r = 0.247*), which implies that higher ET values areof fundamental importance for increasing grain yield during cropproduction. Interestingly, rainfall was significantly positively cor-related with grain yield in wheat seasons (r = 0.843**), but not inmaize seasons, and the correlation was negative for rotation annu-als.

4. Discussion

4.1. Conservation tillage improved soil quality

Soil nutrients are one of the most important factors affectingsoil health and agro-ecosystem productivity (Nael et al., 2004). Theconcentration of OM, total N, available P and available K are partic-ularly important for evaluating soil quality. Our results indicatedthat tillage clearly affected nutrient availability in topsoil in thewheat–maize rotation system, of which conservation tillage (SSMand RSM treatments) increased OM in topsoil (0–0.20 m) by 5.65%and 4.77% after eight years of tillage management, respectively(Fig. 2a). This increase in OM may be attributed to a combina-tion of straw mulching with subsoiling, as reported by Wang et al.(2014b) who found that this tillage approach improved OM in top-soil (0–0.30 m) by 31.2% in rainfed areas of Northeast China after a12-year treatment.

Although some reports suggest a no tillage approach can signif-icantly increase OM in topsoil in semiarid or dry climates (Arshadet al., 1990), the NTSM treatment did not increase OM in the presentstudy which indicated that subsoiling may be more important forimproving soil nutrients in dry-land areas. Other studies showedthat single straw mulching resulted in higher concentrations ofOM than treatments without mulching (Dolan et al., 2006). How-ever, Wang et al. (2014a) showed that 50% crop straw mulchinghad a negative effect on OM. In general, straw mulching with sub-soiling appears to be conducive to accelerating straw rotting anddecreasing soil compaction (Mohanty et al., 2007).

Wang et al. (2014b) also reported that SSM decreased total Nin the top 0–0.10 m, although no difference was observed belowa depth of 0.10 m in Chromic Cambisol at an alkaline pH of 8.9 inNortheast China. However, Dikgwatlhe et al. (2014) found that bothSSM and NTSM increased total N in the topsoil layer, comparedwith CT. In our study, NTSM barely increased total N (0.29%) intopsoil (0–0.20m) by the end of the 8-year study, whereas SSM andRSM treatments increased total N by 7.02% and 4.47%, respectively(Fig. 2b).

Although total P and total K were not increased in topsoil(0–0.20 m), we found significant improvements in available P andavailable K following NTSM (3.8% and 13.6%), SSM (37.8% and 37.5%)and RSM (36.9% and 25.0%) treatments, compared with CT, by theend of the study period in 2012 (Fig. 2c–f). The higher availability

of both P and K following conservation tillage (compared to CT)may be due to the effects of returning straw over several years,and also to the degree of decomposition of the returned straw indifferent treatments. This result is consistent with the findings of

Y. Shao et al. / Europ. J. Agronomy 81 (2016) 37–45 43

Table 3Wheat and maize grain yield and its components in the four tillage approaches during 2008–2012.

Treatments Wheat (Triticum aestivumL.) Maize (Zea mays L.)

Spikes Kernels per spike 1000 kernel mass Grain yield Spikes Kernels per spike 100 kernel mass Grain yield(×104ha−1) (Grain) (g) (kg ha−1) (×104ha−1) (Grain) (g) (kg ha−1)

2008–2009 CT 487.5 c 32.7 b 38.9 a 4798 c 4.10 b 463.7 b 37.1 a 5965 bNTSM 548.9 b 33.7 b 38.3 ab 5607 a 4.24 ab 493.2 a 34.6 c 6292 bSSM 564.0 a 35.5 a 36.3 b 5484 a 4.38 a 432.8 c 36.9 ab 6238 bRSM 491.9 c 32.9 b 37.2 ab 5052 b 4.20 ab 490.9 ab 35.7 bc 6981 a

2009–2010 CT 385.5 b 34.2 b 54.2 a 5375 b 4.31 a 501.6 c 36.4 a 7528 cNTSM 451.5 a 36.8 a 52.4 ab 5847 ab 4.41 a 508.9 c 34.7 b 8205 bSSM 463.5 a 33.4 b 50.2 b 6084 a 4.31 a 540.1 b 36.0 a 8463 bRSM 460.0 a 35.8 ab 51.6 ab 5789 ab 4.55 a 549.8 a 37.0 a 9293 a

2010–2011 CT 285.5 a 25.5 c 37.6 b 2031 b 4.21 b 472.5 c 24.5 b 4635 bNTSM 283.5 a 29.8 ab 41.2 a 2594 a 4.31 ab 694.2 a 27.9 a 5859 aSSM 298.5 a 29.0 b 41.3 a 2513 a 4.27 b 536.2 b 27.4 a 5748 aRSM 294.0 a 30.5 a 41.2 a 2588 a 4.43 a 550.4 b 28.0 a 5879 a

2011–2012 CT 481.5 b 34.3 a 51.6 a 6729 b 4.18 b 348.0 c 30.9 b 3851 cNTSM 489.0 b 34.0 a 49.4 a 6956 ab 4.20 b 396.2 b 31.3 ab 4579 bSSM 516.0 a 32.9 a 50.6 a 7118 a 4.22 b 376.7 bc 31.9 a 4676 bRSM 516.0 a 33.7 a 50.5 a 7004 ab 4.40 a 428.6 a 31.6 ab 5242 a

Source of variance (P)Year 0 0 0 0 0 0 0 0Tillage 0 0 0 0 0 0 0 0Year × Tillage 0 0 0 0.014 0 0 0 0.001

Means within the same annual column followed by different lowercase letters are significantly different at P < 5%.

Table 4Pearson correlation of rainfall, ET, yield and WUE in the four tillage approaches during 2008–2012.

Items Wheat (Triticum aestivum L.) Maize (Zea mays L.) Annual of wheat and maize

Rainfall ET Yield WUE Rainfall ET Yield WUE Rainfall ET Yield WUE

Rainfall 1 1 1ET 0.555** 1 0.293* 1 −0.544** 1Yield 0.843** 0.769** 1 0.070 0.307* 1 −0.539** 0.247* 1WUE −0.0.101 −0.781** −0.222 1 −0.338* −0.658** 0.495** 1 −0.053 −0.566** 0.655** 1

W3dtiTi

4

m2(iprti1tttrsearb

* Correlation is significant at P < 5% (2-tailed).** Correlation is significant at P < 1% (2-tailed).

ang et al. (2014b), who found that SSM increased available P by0.5% in the uppermost 0–0.10 m of topsoil. However, our resultsiffer from those of Wang et al. (2014b), who reported a substan-ial increase in OM after a 12-year treatment, compared to a slightncrease in total N and OM in topsoil after our 8-year experiment.his apparent discrepancy could be due to the shorter time period

n our study.

.2. Conservation tillage increased WUE

In the wheat season, a no tillage or minimum tillage with strawulching was shown to increase soil water content (Sharma et al.,

011), and improve WUE by 17.2–17.5% in arid northwest ChinaHuang et al., 2012). Similarly, WUE in wheat and maize werencreased by 30.1% and 6.8%, respectively, in a wheat-maize crop-ing system (He et al., 2009). The results of the present studyevealed that all three conservation tillage (NTSM, SSM and RSM)reatments decreased ET, by 19.2%, 26.5% and 28.5%, respectively,n the wheat season, and increased mean WUE by 24.6%, 15.9% and5.7% in wheat, maize and annual seasons (averaged across threereatments and 4 years, Table 2). Meanwhile, WUE was improvedo a greater extent in wheat than in maize, and we attributed thiso the uneven rainfall distribution (Fig. 3): only 12–49% of annualainfall fell in the wheat season, during which water collection andtorage was higher for 230 days. The RSM treatment gave the high-

st mean annual WUE (20.7% above CT), followed by SSM (15.1%)nd NTSM (11.2%) (Table 2, Fig. 3). These results indicated thatidge planting and straw mulching promote better use of rainfally improving soil water storage (Fuentes et al., 2003). These results

also suggest that straw mulching may help to enhance collection ofnatural precipitation, and minimize soil water loss to ensure effi-cient uptake and utilization of soil water throughout the entirewheat growing season. Deep ploughing without straw mulching,which is practiced widely in CT treatments in irrigated crop pro-duction areas in northern China, markedly increased soil water lossvia evapotranspiration (Munawar et al., 1990). In contrast, strawmulching, as performed in the three conservation tillage treatmentsin this study, were superior at retaining deep soil water and pre-venting evaporation. Thus, the RSM tillage approach appears to beparticularly well-suited for improving annual WUE in wheat-maizerotation systems in rainfed areas.

4.3. Conservation tillage improved crop yield in wheat-maizeannual production

Different conservation tillage approaches are of considerableimportance for crop yield, and a no tillage or minimum tillageapproach with residue retention has recently been widely adoptedin many countries in an attempt to increase crop yield whilst reduc-ing soil erosion and environmental degradation (Wang et al., 2007).In the present study, minimum or no tillage with straw mulchingincreased winter wheat yield by 7.9–12.0%, summer maize yield by13.4–24.6%, and annual crop yield by 12.3–16.9%, compared withCT (Table 2). Similar results were reported by Fuentes et al. (2003)

who found that a no tillage treatment increased winter wheat yieldby 39.7% in a single cropping system in a dry-land area of Wash-ington State, USA. This increase in yield was attributed to increasedwater availability during spring under the no tillage system. Most

4 Agron

scmpecsyapvwca

lsa(c(sseosywtgia

ty(trsewad

5

tydwfcMaoaSr

A

N2

4 Y. Shao et al. / Europ. J.

tudies in Europe suggest that the yield of long-term no tillagerops tend to approach or exceed that of conventional ploughingethods (Grandy et al., 2006; Soane et al., 2012). However, soil

roperties, crop system and weather factors greatly influence thexperimental results. For example, the no tillage yield for wheat onlay soils in Finland was as low as 60–80% that of a ploughing-basedystem (Känkänen et al., 2011). In contrast, barley (Hordeum L.)ield can be twice that of conventional tillage in extremely aridreas in northern Spain (Fernández-Ugalde et al., 2009). In theresent study, the mean yield increment across all three conser-ation tillage treatments was 17.4% for maize but only 10.3% forheat. This discrepancy was likely due to the higher average pre-

ipitation (381 mm) during the maize growing season (566 mmveraged across the 4 years; Fig. 4).

Comparative analysis of various yield parameters showed thatess precipitation (only 76 mm) during the wheat growing sea-on of 2010–2011 resulted in decreased spike number per unitrea (42.0%), kernels per spike (14.8%) and thousand grain mass20.2%), which ultimately led to a 65.0% decrease in wheat yield,ompared with a typical year experiencing normal precipitation229.3 mm in 2011–2012; Table 3, Fig. 4). This result suggests thatoil water shortage in dry-land wheat planting areas mainly affectspike number. The summer maize season of 2011–2012 experi-nced the least rainfall (466.3 mm), which was 14.1% less than thatf 2009–2010. This resulted in fewer spikes (3.4%), fewer grains perpike (26.2%), lower hundred grain weight (12.7%) and lower grainield (45.2%; Table 3). A decrease in the number of kernels per earas the major cause of yield reduction in summer maize. Taken

ogether, these results suggest that different management strate-ies should be considered and performed in order to minimize thenfluence of drought on winter wheat and summer maize in rainfedreas.

Furthermore, in the present study, correlation analysis showedhat rainfall was significantly positively correlated with wheatield, but no such relationship was apparent with maize yieldTable 4). This result suggested that rainfall is likely to be one ofhe most important factors affecting wheat yield in this rainfedegion, and maize may use water less efficiently than wheat whenufficient rainfall is received during the maize season. The appar-nt differences in the correlation between ET, yield and WUE inheat, maize and rotation annuals also implies that a varied tillage

pproach should be adopted to improve crop yield and WUE forifferent crops.

. Conclusions

This experiment assessed the effects of different conservationillage approaches on soil nutrients, water use efficiency and grainield in winter wheat and summer maize systems in a rainfedry-land farming area of northern China. Minimum or no tillageith straw mulching (especially SSM and RSM treatments) was

ound to increase the concentration of important nutrient indi-ators (especially available P, available K and OM) in topsoil.eanwhile, conservation tillage approaches also increased WUE

nd grain yield in wheat, maize and rotation annual crops. Therder of effectiveness was SSM > NTSM > RSM for wheat production,nd RSM > SSM > NTSM for maize and annual production. Therefore,SM and RSM appear to be most appropriate conservation tillageegimes for this rainfed agro-ecosystem in northern China.

cknowledgements

This work was supported by grants from the Twelfth Five-Yearational Food Production Technology Project (2013BAD07B07 and015BAD26B01), the National Natural Science Foundation of China

omy 81 (2016) 37–45

(31272246) and the Special Fund for Agro-scientific Research in thePublic Interest (201203079 and 201203031).

References

Arshad, M., Schnitzer, M., Angers, D., Ripmeester, J., 1990. Effects of till vs no-till onthe quality of soil organic matter. Soil Biol. Biochem. 22, 595–599.

Bhatt, R., Khera, K.L., 2006. Effect of tillage and mode of straw mulch application onsoil erosion in the submontaneous tract of Punjab. Indian Soil Tillage Res. 88,107–115.

Bossio, D., Geheb, K., Critchley, W., 2010. Managing water by managing land:addressing land degradation to improve water productivity and rurallivelihoods. Agric. Water Manage. 97, 536–542.

Chu, P., Yu, Z., Wang, D., Zhang, Y., 2010. Effects of tillage on water consumptioncharacteristics and grain yield of wheat. Sci. Agric. Sin. 19, 008.

Dikgwatlhe, S.B., Chen, Z.-D., Lal, R., Zhang, H.-L., Chen, F., 2014. Changes in soilorganic carbon and nitrogen as affected by tillage and residue managementunder wheat?maize cropping system in the North China Plain. Soil Tillage Res.144, 110–118.

Dolan, M.S., Clapp, C.E., Allmaras, R.R., Baker, J.M., Molina, J.A.E., 2006. Soil organiccarbon and nitrogen in a Minnesota soil as related to tillage: residue andnitrogen management. Soil Tillage Res. 89, 221–231.

Fernández-Ugalde, O., Virto, I., Bescansa, P., Imaz, M., Enrique, A., Karlen, D., 2009.No-tillage improvement of soil physical quality in calcareous,degradation-prone, semiarid soils. Soil Tillage Res. 106, 29–35.

Fuentes, J.P., Flury, M., Huggins, D.R., Bezdicek, D.F., 2003. Soil water and nitrogendynamics in dryland cropping systems of Washington State. U.S.A. Soil TillageRes. 71, 33–47.

Grandy, A., Robertson, G., Thelen, K., 2006. Do productivity and environmentaltrade-offs justify periodically cultivating no-till cropping systems? Agron. J. 98,1377–1383.

He, J., Wang, Q.J., Li, H.W., Liu, L.J., Gao, H.W., 2009. Effect of alternative tillage andresidue cover on yield and water use efficiency in annual double croppingsystem in North China Plain. Soil Tillage Res. 104, 198–205.

Huang, G.B., Chai, Q., Feng, F.X., Yu, A.Z., 2012. Effects of different tillage systems onsoil properties root growth, grain yield, and water use efficiency of winterwheat (Triticum aestivum L) in Arid Northwest China. J. Integr. Agric. 11,1286–1296.

Islam, M.R., Hu, Y., Mao, S., Mao, J., Eneji, A.E., Xue, X., 2011. Effectiveness of awater-saving super-absorbent polymer in soil water conservation for corn (Zeamays L.) based on eco-physiological parameters. J. Sci. Food Agric. 91,1998–2005.

Känkänen, H., Alakukku, L., Salo, Y., Pitkänen, T., 2011. Growth and yield of springcereals during transition to zero tillage on clay soils. Eur. J. Agron. 34, 35–45.

Lenka, S., Singh, A.K., Lenka, N.K., 2009. Water and nitrogen interaction on soilprofile water extraction and ET in maize–wheat cropping system. Agric. WaterManage. 96, 195–207.

Lentz, R., Bjorneberg, D., 2003. Polyacrylamide and straw residue effects onirrigation furrow erosion and infiltration. J. Soil Water Conserv. 58, 312–318.

Mohanty, M., Bandyopadhyay, K.K., Painuli, D.K., Ghosh, P.K., Misra, A.K., Hati, K.M.,2007. Water transmission characteristics of a Vertisol and water use efficiencyof rainfed soybean (Glycine max (L:) Merr) under subsoiling and manuring. SoilTillage Res. 93, 420–428.

Munawar, A., Blevins, R., Frye, W., Saul, M., 1990. Tillage and cover cropmanagement for soil water conservation. Agron. J. 82, 773–777.

Nael, M., Khademi, H., Hajabbasi, M., 2004. Response of soil quality indicators andtheir spatial variability to land degradation in central Iran. Appl. Soil Ecol. 27,221–232.

Nyssen, J., Poesen, J., Moeyersons, J., Haile, M., Deckers, J., 2008. Dynamics of soilerosion rates and controlling factors in the Northern EthiopianHighlands–towards a sediment budget. Earth Surf. Processes Landforms 33,695–711.

Olsen, S.R., 1954. Estimation of Available Phosphorus in Soils by Extraction withSodium Bicarbonate. United States Department Of Agriculture, Washington.

Page, A.L., Miller, R.H., Keeney, D.R., 1982. Total carbon, organic carbon, andorganic matter. Methods Soil Anal., 539–579.

Sharma, P., Abrol, V., Sharma, R., 2011. Impact of tillage and mulch management oneconomics, energy requirement and crop performance in maize-wheatrotation in rainfed subhumid inceptisols, India. Eur. J. Agron. 34, 46–51.

Shipitalo, M.J., Dick, W.A., Edwards, W.M., 2000. Conservation tillage andmacropore factors that affect water movement and the fate of chemicals. SoilTillage Res. 53, 167–183.

Sisti, C.P., dos Santos, H.P., Kohhann, R., Alves, B.J., Urquiaga, S., Boddey, R.M., 2004.Change in carbon and nitrogen stocks in soil under 13 years of conventional orzero tillage in southern Brazil. Soil Tillage Res. 76, 39–58.

Soane, B.D., Ball, B.C., Arvidsson, J., Basch, G., Moreno, F., Roger-Estrade, J., 2012.No-till in northern, western and south-western Europe: a review of problemsand opportunities for crop production and the environment. Soil Tillage Res.118, 66–87.

Turner, M.G., 1989. Landscape ecology: the effect of pattern on process. Annu. Rev.Ecol. Syst., 171–197.

Wang, X.B., Cai, D.X., Hoogmoed, W.B., Oenema, O., Perdok, U.D., 2007.Developments in conservation tillage in rainfed regions of North China. SoilTillage Res. 93, 239–250.

Agron

W

W

W

W

associated traits in winter wheat cultivars in the North China Plain. Agric.Water Manage. 97, 1117–1125.

Zhang, X., Wang, S., Sun, H., Chen, S., Shao, L., Liu, X., 2013. Contribution of cultivar,

Y. Shao et al. / Europ. J.

ang, Y., Xie, Z., Malhi, S.S., Vera, C.L., Zhang, Y., Wang, J., 2009. Effects of rainfallharvesting and mulching technologies on water use efficiency and crop yieldin the semi-arid Loess Plateau. China Agric. Water Manage. 96, 374–382.

ang, J., Zhang, H., Li, X., Su, Z., Li, X., Xu, M., 2014a. Effects of tillage and residueincorporation on composition and abundance of microbial communities of afluvo-aquic soil. Eur. J. Soil Biol. 65, 70–78.

ang, Q., Lu, C., Li, H., He, J., Sarker, K.K., Rasaily, R.G., Liang, Z., Qiao, X., Li, H.,

Mchugh, A.D.J., 2014b. The effects of no-tillage with subsoiling on soilproperties and maize yield: 12-Year experiment on alkaline soils of northeastChina. Soil Tillage Res. 137, 43–49.

esterman, R.L., 1990. Soil Testing and Plant Analysis. Soil Science Society ofAmerica Inc.

omy 81 (2016) 37–45 45

Wright, A.L., Hons, F.M., Matocha, J.E., 2005. Tillage impacts on microbial biomassand soil carbon and nitrogen dynamics of corn and cotton rotations. Appl. SoilEcol. 29, 85–92.

Zhang, X., Chen, S., Sun, H., Wang, Y., Shao, L., 2010. Water use efficiency and

fertilizer and weather to yield variation of winter wheat over three decades: acase study in the North China Plain. Eur. J. Agron. 50, 52–59.