Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/1/2005
Publication Date: 4/4/2005
Citation: Wienhold, B.J. 2005. Changes in soil attributes following low p swine slurry application to no-tillage sorghum. Soil Science Society of America Journal 69:206-214. Interpretive Summary: Swine manure can serve as an excellent fertilizer source for crops. Adding swine manure to soils can effect other soil properties influencing environmental and agronomic soil functions. Swine manure often contains phosphorus in excess of what can be used by the crop. Accumulations of phosphorus in the soil increases the potential for contamination of surface waters when phosphorus is transported in runoff or erosion. Manure for swine fed low phytate corn diets contains less phosphorus reducing accumulation in the soil and the potential for water contamination. The effect of low phytate manure on other soil properties is unknown. A number of physical, chemical, and biological soil properties were measured each spring from 1999 to 2002 on no-tillage sorghum soils treated with inorganic fertilizer, manure from swine fed traditional corn diets, manure from swine fed low phytate corn diets, and a no treatment control. Nutrient treatments were applied each spring from 1999 to 2001. Physical and chemical soil properties measured should not inhibit crop growth. Extractable phosphorus increased in both manure treatments and the increase was greater with manure from swine fed traditional corn diets. Biological soil properties increased in manure treatments and decreased in the control or inorganic fertilizer treatment. A soil quality index was used to assess changes over time for the soil properties measured. Index values increased slightly in the inorganic fertilizer and control treatments under continuous no-tillage sorghum. Index values increased at a faster rate in the two manure treatments due to combined effects of manure additions and no-tillage sorghum. Use of low phytate manure improved soil quality and has reduced potential for soil phosphorus accumulation.
Technical Abstract: Swine (Sus scrofa) slurry can serve as an excellent fertilizer source. Repeated application at crop N rates results in excess soil P due to low N:P ratios in swine slurry. Low phytate (LP) corn (Zea mays L.) stores a greater proportion of P as phosphate increasing bioavailability of P in pig feed grain. Improved utilization of feed P reduces P concentration in manure and reduces soil P accumulation. Effect of manure from swine fed LP grain on other soil properties is not known. Changes in soil attributes over four years were compared for soils receiving LP manure, manure from swine fed traditional corn (TC) diets, inorganic fertilizer, and no nutrients in no-tillage sorghum (Sorghum bicolor [L.] Moench) on a Sharpsburg clay loam (Fine, smectitic, mesic Typic Argiudolls). Physical soil properties exhibited values that should not inhibit crop growth. Chemical soil properties responded to time and treatment. Particulate organic matter (POM) increased with years. Nitrate-N, pH, and extractable P increased with manure additions. Extractable P content in surface layers and the 0- to 30-cm increment were greater with addition of TC manure than LP manure. Chemical soil properties exhibited values acceptable for crop production but increasing extractable P, especially with TC manure, increases the potential for environmental contamination. Biological soil properties varied in their response to treatments. Potentially mineralizable N increased over time while microbial biomass C decreased in the control and increased in manure treatments. A soil quality index was used to conduct a dynamic soil quality assessment. Soil quality index values increased 10% over years in the control and inorganic fertilizer treatments likely due to inputs of recalcitrant sorghum residue that increased POM and potentially mineralizable N. Soil quality index values increased 40% in manure treatments, due to inputs of highly available nutrients and manure organic C combining with sorghum residue to improve POM, microbial biomass C, and extractable P. Manure additions improved soil properties affecting crop production with P accumulation and the potential for environmental contamination being lower with LP manure.