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Title: Compost input effects on dryland wheat and forage yields and soil quality

Author
item Calderon, Francisco
item Vigil, Merle
item Benjamin, Joseph

Submitted to: Pedosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2017
Publication Date: 6/1/2018
Citation: Calderon, F.J., Vigil, M.F., Benjamin, J.G. 2018. Compost input effects on dryland wheat and forage yields and soil quality. Pedosphere. 28(3):451-462.

Interpretive Summary: This study evaluated the use of compost to meet fertility requirements in organic wheat and forage rotations under dryland semiarid conditions. Three rates of compost (none added (0X), 22.9 T ha-1 (1X), and 108.7 T ha-1 (5X)) were applied every other year from 2010-2015. Our results show that after several years of transition from grassland to crop production, compost had little benefit in terms of wheat grain yields, but compost did enhance triticale/pea forage production. Compost was effective in increasing soil C and N, but high rates of compost resulted in excessive soil P concentration. Soil microbial function measured as soil enzyme activities was increased by the addition of high rates of compost.

Technical Abstract: Demand for organically produced grain and forage has increased in recent years, as well as the interest in the use of beef feedlot compost to meet crop N and P demands. This study evaluated three rates of compost (none added (0X), 22.9 T ha-1 (1X), and 108.7 T ha-1 (5X)) on two dryland cropping systems in the Central Great Plains of the USA: A wheat (Triticum aestivum)-fallow (WF) rotation harvested for grain, and a triticale (Triticosecale)/pea (Pisum sativum)-fallow (T/P-F) rotation harvested for forage. The experiment started in the fall of 2010 and data was collected until 2015. During this time, compost was applied pre-plant three times (every other year), and four crop harvests were collected. Variables measured included grain and forage yields, grain quality, forage quality, soil total C and total N, soil extractable P, and soil enzyme activities. The average forage T/P-F biomass for the four harvest years was higher in the 5X compost treatment relative to the 0X. The 1X rate had no significant effect on T/P-F biomass yield. Wheat biomass did not increase with compost addition, but the 1X and 5X treatments had higher wheat biomass N content than the 0X. Compost additions did not increase wheat grain yields at a p<0.05 level in any of the four years sampled. However, wheat grain zinc content was increased incrementally by the compost rates after three compost applications. Soil total C and N increased with the 5X compost addition after three compost applications, but not with the 1X rate. Soil extractable P increased with compost addition, and reached excessive levels on the 5X treatment. Soil enzyme activities (associated with N and C cycling) were higher in the presence of a growing wheat crop compared to fallow, and also responded positively to the 5X compost treatment. The activity of phosphatase was not significantly affected by either fallow or compost additions. These results show that beef feedlot compost is effective in enhancing forage yields, wheat grain quality, soil C, and N, as well as specific microbial enzymes important for nutrient cycling. However, the large amounts of compost necessary to elicit these positive responses did not increase grain yields, and also resulted in an excessive buildup of soil P.