Soil Acidity, Lime, and Phosphorous Brian Arnall Hailin Zhang Chad Godsey Department of Plant and Soil Sciences Oklahoma State University

Median Soil pH Values of OK Counties (all Ag. soils) 2007 Wheat Fields: Canadian5.4 Garfield5.4 Grant5.4 Kay5.7

Production Induced Soil Acidity No-till Normal tillage

Plant grown under aluminum toxic conditions compared with a normal pant the same age.

pH 5.1 vs 4.5

Acidity and Wheat

Acidity and Sorghum Relative yields of Wheat with Sorghum Ylds and Price

Acidity and Corn

How to deal with acid problems? Band phosphate fertilizer with seeds to tie up Al Plant Al tolerant wheat varieties Apply aglime to neutralize acidity

Winter Wheat Response to Acid Soil Management 0-Lime 0-P 2 O 5 0-Lime 40-P 2 O 5 Banded 0-Lime 40-P 2 O 5 Broadcast

Apr-90 Apr-00Aug-08 Apr

In the Past OSU recommended banding P on low pH soils when pH was low, on rented land, so that high cost of liming was avoided. Today price to takes $16/ac/yr to counteract acidity. Lime at $/ton 2.5 yrs of P in 1 year. Effects last much longer. Risk is in volatile P prices.

Variety Response to Soil pH Custer, Ok101, Jagalene, Jagger, 2174, AP502Cl, Ok102, 2137 Limed Not Limed

Winter Wheat Response to Acid Soil Management 2 T Alum 0 T Lime pH 4.4 NDVI T Alum Lime to BI 6.5 pH 5.9 NDVI 0.70

Cost and Benefit at 1.25 tons/A Cost

Soil pH changes with time after lime was applied at 7 lime rates (t/ac ECCE).

Particle Size Determines Lime Reactivity Lime reacted in 1 to 3 years, % Finer particle size (logarithmic scale of mesh size)

Ag LimePelletized Lime

Soil pH - CLB (Five years after lime application) *L *L Indicates significant treatment effect at α=0.05. *L

Placement Another important factor determining the effectiveness of lime

Annual Changes in Soil pH for the 8400 kg ECC ha -1 treatment at Site MS

Conclusion 1:1 soil pH increased in the surface 7.5 cm with the surface application of lime. Reaction of the lime with the soil was still occurring 3 to 5 years from the date of application. Reducing recommended lime application rates for no-tillage systems. –Assuming 7.5 cm depth of incorporation –Frequency does not matter Differences in liming material were not detected

Lime Referenc e Strip Nitrogen strip Introduce a Lime Reference Strip used with or without an N- rich strip in acid soils to show the benefits of liming

RI = 1.11 NDVI = 0.57NDVI = 0.64 pH 5.5, Limed pH 7.0 pH 5.5, not Limed

Misperceptions Does using anhydrous ammonia acidify soil faster? Does using anhydrous ammonia kill my worms?

Lime required to neutralize the soil acidity produced by fertilizers if all ammonium-N is converted to nitrate-N. Nitrogen sourceComposition Lime required (lb CaCO 3 / lb N) Anhydrous ammonia Urea Ammonium nitrate Ammonium sulfate Monoammonium phosphate Diammonium phosphate Triple super phosphate Adapted from Havlin et al., 1999.

Vigorous crop (Shoot/Root) growth Improved resource utilization water, nutrients positive environmental implications Better resistance to stress disease, pest, moisture, temperature Earlier maturity good grain & fruit development better crop quality, yield P impact on crops

Soil pH and P Availability –In acid soils P precipitates as insoluble Fe and Al minerals –In neutral and calcareous soils P precipitates as insoluble Ca phosphates –Soil P is most available in the pH range of 6 to 6.7

Mineralogy/Soil Type and P Retention More weathered soils of Eastern OK tend to sorb P onto Fe and Al oxides Less weathered soils of Western OK tend to precipitate P as calcium phosphates General Distribution pattern of clay minerals in Oklahoma: M – montorillonite, l – illite, K kaolinite, V – vermiculite, C – chlorite, 1 : >35%, 2 : 20-35%, 3: 10-20%, 4: <10%

Summary Plants uptake P from solution, as supplied by the soil –P moves to plant roots slowly by diffusion –The ability of the soil to maintain solution P levels is the buffer capacity (heavy soils more buffered than sandy soils) Most P added will not be plant available –Soil pH has big impact on P availability Optimum pH ~ 6.5 Fertilizer P can effect soil pH

Questions?