Overview of S Management & Related Usefulness of Soil

Testing

David H. Hardy

Section-Chief, Soil Testing

Agronomic Division, NCDA&CS

SERA 6 Meeting

June 21, 2011

• Ordinary superPO4-2 (0-20-0) not used

– 12% S

• Higher yields via varieties and management = more S demand

• Cleaner air due to air quality regulation

Increased Importance of Today

Sulfate Wet Deposition Trends NADP database - current eastern NC estimate

(wet + dry deposition: approx 8 lb S/ac/yr)

IPNI 2010 Soil Summary

Subsoil S Reserves

• Subsoil where topsoil not managed– 68 ppm S

• Subsoil where topsoil managed– 138 ppm S

Hardy MS thesis, 1983

Sulfur Deficiency

Sulfur Deficiency Symptoms

Sulfur Deficiency

Sulfur Deficiency Symptoms

Plants are yellow and stunted.

Soil Sulfur – Corn Yellow

0

5

10

15

20

25

30

35

0 1 2

Su

lfu

r In

dex

n = 37, mean = 23

Green corn:

S-I = 30

Plant Tissue Levels

• Yellow corn

• 0.14% S

• N:S = 26

• Green corn

• 0.18% S

• N:S = 22

S Studies 2005 & 2006• Validate plant response to soil S levels using M3

for both wheat and corn

• Responsive and nonresponsive site– Based on surface M3 = 12 ppm

• S source- pelletized gypsum

• S rates- 0, 11, 22, 45 kg ha-1 – Applied broadcast after planting for corn

• Split for wheat at two higher rates

S Studies 2005 & 2006

• Soil samples at study initiation and V6– Depth A: 0 to 10 cm- NT; 0 to 15 cm- CT– Depth B: 10 to 20 cm- NT; 15 to 30 cm- CT

• Plant tissue at V6 and VT

• Yield

Soil data for 2005 locations.

Location

Surface

Texture

Taxonomic

Name Initial Soil S

Depth A Depth B

----mg dm-3----

Bertie loamy sand Typic Udipsamment 15 20

Edgecombe-1 f. sandy loam Aquic Paleudult 12 24

Edgecombe-2* loamy sand Arenic Kandiudult 13 12

Greene* fine sand Arenic Hapludult 13 11

Hyde mucky sandy loam

Umbric Endoudalf 14 20

Martin f. loamy sand Aquic Paleudult 16 14* Predicted responsive site based on S in topsoil being ~ 12 mg dm-3 or less.

Hyde Co, Armstrong Farms, muck, 2005(only significant response was in V-6 plant tissue S)

020406080

100120140160180200

0 10 20 30 40

S Fertilizer rate (lb/ac)

Grain Yield (bu/ac)

Soil S, 0-8" (index)

Leaf S, V-6 (% x 100)

Leaf S, VT (% x 100)

0

20

40

60

80

100

0 10 20 30 40

S Fertilizer rate (lb/ac)

Grain Yield (bu/ac)Soil S, 0-8" indexLeaf S, V-6 (% x 100)Leaf N:S ratio

a

b

abab

Edgecombe-2, 2005

•Soil S

•0 – 9

10 – 10

20 – 11

40 –15

020406080

100120140160180

0 10 20 30 40

S Fertilizer rate (lb/ac)

Grain Yield (bu/ac)Soil S, 0-8" indexLeaf S, V-6 (% x 100)Leaf N:S ratio

Greene, 2005

aa

a

a

•Soil S

•0 – 11

10 – 13

20 – 13

40 –18

Bladen Co., 2006

0102030405060708090

100

0 10 20 30 40

S Fertilizer rate (lb/ac)

Grain Yield (bu/ac)

Soil S, 0-8" index

Leaf S, V-6 (% x 100)

Leaf N:S ratio

a

b

aa

•Soil S

•0 – 10

10 – 10

20 – 11

40 –10

S Studies 2005 & 2006 Overview

• 2005, 1 of the 2 predicted sites responded– Greene Co. data is bothersome

• 2006, 1 in 5 predicted sites responded– Weed problems, Organic soil may have

mineralized S…??

• Plant nutrition improved @ V6 on both responsive and nonresponsive sites

Recommendation??Similar Quandary as Nitrogen

• Highly leachable as nitrate but subsoil S

• Mineralization / immobilization issue

• However, possibly overlooked, unlike N

• Easy to acquire value from ICP, unlike N

Current S Recommendations

• Soil critical level: 12 ppm = 25 S-I – 15 to 25 lb per acre of S depending on soil class

• Know your soils– Consider S fertilizer if 18+” surface sand

• Plant tissue sample