ENHANCED MIDWESTERN CROPPING SYSTEMS FOR SUSTAINABILITY AND ENVIRONMENTAL QUALITY
Location: Agroecosystems Management Research Unit
Title: Soil Phosphorus Distribution in a Crop Production System with Long-term Compost Amendment
Submitted to: World Congress of Soil Science
Publication Type: Proceedings
Publication Acceptance Date: February 17, 2010
Publication Date: August 6, 2010
Citation: Bortolon, L., Kovar, J.L., Cambardella, C.A., Singer, J.W., Gianello, C. 2010. Soil Phosphorus Distribution in a Crop Production System with Long-term Compost Amendment. In: Gilkes, R.J. and Prakongkep, N. (ed). Proceedings of the 19th World Congress Soil Science, August 1-6, 2010, Brisbane, Australia. ISBN 978-0-646-53783-2. DVD.
Interpretive Summary: Phosphorus (P) fertilizer is essential for maintaining high yields of agronomic crops. Organic amendments, such as manure and compost, are an economical alternative to commercial fertilizers for supplying P to crops. To better understand how plants capture P from soil amended with compost, rather than fertilizer, we should know how plant-available P is distributed in the topsoil. In this study, we evaluated P distribution in soil either with or without compost application in a corn-soybean-wheat/clover cropping system managed with intensive, moderate, or no tillage since 1988. We found that long-term compost application increased all P forms in the soil profile, especially the types of P most susceptible to loss by leaching and runoff. We also found that tillage affected P distribution more than the type of crop that was grown, and that less tillage meant that more P remained in topsoil layers where root activity is higher. These results should be of value to commercial growers and conservationists, as well as the organic farming community.
Excessive fertilization with inorganic or organic phosphorus (P) amendments, such as compost, increases the risk of P losses to surface waters. To properly manage fertilizer amendments, an understanding of P distribution in soil is essential. The objective of this research was to evaluate P distribution in soil with and without long-term compost amendment in a maize (Zea mays L.)-soybean (Glycine max L. Merr.)-wheat (Triticum aestivum L.)/clover (Trifolium repens L.) crop rotation managed with moldboard plow (MP), chisel plow (CT), or no-tillage (NT), with all phases present each year since 1988. Soil (Clarion silt loam and Canisteo silty clay loam) samples were collected in 2007 from three depth increments (0-7.5; 7.5-15; 15-30 cm) of each plot. Water-extractable P, Bray-1 extractable P, total P, and degree of P saturation (DPS) were determined from subsamples. Long-term compost application increased all P forms in the soil profile. The low C:P ratio of the compost likely increased soil P mineralization, leading to the differences we measured. The intensity of tillage affected all measures of P in the surface soil more than the crop that was grown. Water-extractable P was higher in the CT and NT treatments relative to the MP treatment, and tended to be higher following soybean. Similar results were found for Bray 1 P and total P. Compost applications can increase soil P, mainly P forms most susceptible to losses, thereby increasing the risk of P losses by leaching and runoff. Conservation tillage can reduce P leaching by keeping P in topsoil layers where root activity is higher. To decrease the risk of P losses from these cropping systems, compost applications should be P based.