LONG-TERM APPLICATION OF POULTRY LITTER TO IMPROVE SOIL AGGREGATE STABILITY UNDER COOL AND WARM SEASON GRASSES

Abstract

Farming practices such as organic and inorganic amendment and soil type can affect aggregation under forage species. We determined the effect of nitrogen rate and soil-litter history on short-term response of aggregate stability under tall fescue (Festuca arundinaceae Schreb.), annual ryegrass (Lolium multiflorum Lam.) and bermudagrass (Cynodon dactylon L.). Nitrogen was applied as ammonium nitrate (NH4NO3) at rates 0, 160, 320 kg total N ha-1 in split applications (80 and 160 kg N ha-1 ) to tall fescue, annual ryegrass and bermudagrass grown in 2000g of a litteramended and unamended Bude silt loam (Fine-silty, mixed, active, thermic Aquic Fragiudults) and to bermudagrass in a litter-amended and unamended Ruston sandy loam (Fine-loamy, siliceous, semiactive, thermic Typic Paleudults) in a greenhouse pot experiment. Aggregate stability was measured as water stable macro-aggregate (> 250 µm) and micro-aggregate (125-250 µm) using a wet sieving apparatus. The litter-amended soils produced more dry matter yield per unit of N and had more stable aggregates in comparison to their unamended counterparts. Increasing rate of N decreased aggregate stability in the litter-amended Bude under annual ryegrass and bermudagrass, possibly due to the rapid drying of the soil that resulted from the increase in yield. The results of these studies indicate that the effect of soil type, forage species and fertility management on soil aggregate stability may vary base on environmental condition. Field studies are required to understand the effect of management practices on aggregate stability.