Dairy manure compost quality effects on corn silage and soil properties
Soil nutrients in dairy manure composts vary depending on the original manure or other additives, with consequent effects on crop production. An experiment addressing the effects of single applications of dairy compost of high quality (HQC) or low quality (LQC) at the incorporation rates of 0, 45, and 90 Mg ha-1 on corn (Zea mays L.) silage yields, forage quality, and soil nutrients was conducted in 2004 and 2005. The composts were incorporated prior to planting in 2004, which were also compared with the performance of two commercial fertilizer levels (N-P-K) at high (HIF, 336-98-93) or low rates (LIF, 168-49-47). Compost treatment plots received annual split applications of supplemental inorganic N at 224 or 336 kg ha-1. Through the two growing seasons, corn silage yields ranged from 17 to 25 Mg ha-1 yr-1 depending on compost quality and compost application rates. Corn silage yields in plots with HQC were generally greater than LQC in 2004, but yields did not differ in 2005. Total apparent N recovery did not differ between compost qualities or among compost rates. Soil pH of LQC treatments averaged 8.1 after the second season and remained higher than that of HQC which ranged from 7.4 to 7.6. Electrical conductivity (EC) of soils from HQC plots was 14% lower than that of LQC in 2004 and became similar to that of LQC in 2005. Soil P and K levels in LQC were greater than HQC and were greatest in the 90 Mg ha-1 rate. Based on these data, there is no advantage of using the higher quality compost with greater OM.