Effects of tillage system, crop residue level, and fertilizer application technique on losses of phosphorus and pesticides from agricultural lands

A rainfall simulator was used to study the effectiveness of three best management practices - no-till, residue level and fertilizer application technique - for reducing sediment, phosphorus, and pesticide losses from agricultural lands. Simulated rainfall was applied to 12 experimental field plots, each 0.01 ha in size. The plots were divided into conventional and no-till systems. During phase I, the effectiveness of two fertilizer application methods - subsurface injection and surface application - were investigated for the two tillage systems. In phase II, three crop residue levels - 0, 750, and 1500 kg/ha - were studied within each tillage system. Granular fertilizer was applied at the rate 46 kg/ha. Atrazine and 2,4-D were applied at the rates of 2.24 and 0.56 kg/ha active ingredient, respectively. Fertilizer and herbicides were applied 24 to 48 hours before the start of rain simulation. Water samples were collected from the base of each plot and analyzed for sediment, nutrient, and pesticide content.

No-till was found to be very effective in reducing runoff and sediment losses. No-till with high residue level produced the greatest reductions in runoff and sediment losses, and the highest reduction for both runoff and sediment occurred with no-till and 1500 kg/ha crop residue level. No-till reduced sediment loss by 98% and total runoff volume by 92%. The injection fertilization method reduced 0-P losses by 39% for no-till and 35% for conventional tillage. Reductions in T-P losses due to no-till practice were 89% and 91 % for surface and injection fertilizer application methods, respectively, compared to the conventional system. Averaged across all fertilizer treatments, an equivalent of 0.9% and 8.9% of the total-P fertilizer applied to the plots was lost from no-till and conventional tillage plots, respectively. Concentrations of atrazine and 2,4-0 in runoff and sediment were greater from the no-till plots than from the conventional plots, but total losses were less. Water was the major carrier for both herbicides, although the concentration of 2,4-D in sediment was higher than that of water. Averaged over all plots, the atrazine losses were 2.9% of the applied amount for conventional tillage and 0.3% for no-till. The corresponding values for 2,4-0 were 0.3% and 0.02%.