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Biosolids Effects on Grain Yield and Quality

Ron Jirava
with: Dan Sullivan and Andy Bary, WSU Puyallup; Dan Sturgill, Seattle Metro;
Mikki Kisson, O’Neill and Sons

Objective

Compare biosolids to aqua ammonia for grain yield, test weight and protein.

Location: Ritzville, WA Field history: canola 90; fallow 91; winter wheat 92; fallow 93
Soil: Ritzville silt loam Annual precipitation: 11.5 inches

Treatments

Check (no fertilizer)
Aqua ammonia, 50 lb N/ac, applied 27 May 93
Biosolids, 3, 6, and 9 dry ton/ac, applied 19 Oct 92

Comments

Biosolids from the Renton wastewater treatment plant were applied with a manure spreader to 50 by 1000 ft plots. The biosolids contained 86 lb total N and 22 lb ammonium-N per dry ton and were incorporated on 29 Mar 93 with a skew treader. Tres winter wheat was seeded 8 Sep 93. Growing conditions were above average. Soil moisture was good following the winter of 1992-3. Several inches of rain fell in early June, 1994 as the crop was reaching the grain fill period. At harvest, we cut a 24 by 794 ft strip from the center of each plot. We collected two grain samples from each plot as the grain was augered from the weigh wagon for test weight and total N measurements. Total N was determined with a LECO combustion analyzer. Grain protein was calculated as: LECO total N times 5.75. The aqua ammonia treatment in Rep 4 was lost because of a biosolids application error.

Data

Grain Yield, bu/ac (25 Jul 94)

Treatment Rep 1 Rep 2 Rep 3 Rep 4 Average

Check 43.0 42.3 47.1 52.0 46.1a

Aqua ammonia 52.6 49.2 51.8 51.2ab

Biosolids 3 T/ac 58.7 53.2 52.5 55.5 55.0b

Biosolids 6 T/ac 54.1 54.6 46.8 49.7 51.3ab

Biosolids 9 T/ac 55.1 50.3 45.5 47.8 49.7ab

LSD (5%) 5.7

CV 7

Grain Protein, percent (25 Jul 94)

Treatment Rep 1 Rep 2 Rep 3 Rep 4 Average

Check 8.1 7.5 6.9 8.3 7.7a

Aqua ammonia 8.1 8.6 8.3 8.3a

Biosolids 3 T/ac 12.1 10.9 10.9 11.8 11.4b

Biosolids 6 T/ac 13.2 12.4 12.7 13.2 12.9c

Biosolids 9 T/ac 12.4 12.9 13.8 13.8 13.2c

LSD (5%) 0.8

CV 5

Grain Test Weight, lb/bu (25 Jul 94)

Treatment Rep 1 Rep 2 Rep 3 Rep 4 Average

Check 60.2 60.7 60.2 60.8 60.5b

Aqua ammonia 61.0 60.6 60.6 60.7bc

Biosolids 3 T/ac 61.3 61.2 60.7 61.2 61.1c

Biosolids 6 T/ac 60.2 60.4 60.4 60.6 60.4b

Biosolids 9 T/ac 60.2 59.9 59.5 59.4 59.7a

LSD (5%) 0.4

CV 0.5

Conclusion

The 3 dry ton/ac biosolids application rate produced the highest grain yields and the highest test weight. Higher biosolids application rates (6 and 9 dry ton/ac) produced lower grain yields and lower test weights. The lower test weights (6 and 9 dry ton/ac) were probably due to increased water stress caused by excessive vegetative growth. Grain protein increased with all biosolids application rates, indicating a greater supply of plant-available N in the soil than needed for maximum yield.

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Hans Kok, WSU/UI Extension Conservation Tillage Specialist, UI Ag Science 231, PO Box 442339, Moscow, ID 83844 USA Redesigned by Leila Styer, CAHE Computer Resource Unit; Maintained by Debbie Marsh, Dept. of Crop & Soil Sciences, WSU