Effects of tillage intensity and anionic polyacrylamide on sediment and nitrogen losses in irrigated wheat field

Abstract

Degradation of agricultural soils and nutrient losses affected by intensive agriculture and tillage is of environmental and agricultural concerns. These concerns lead to emergence and development of conservative technologies such as conservation tillage systems [reduced tillage (RT) and no-till (NT)] and anionic polyacrylamide (PAM). A study was done in order to investigate the interactive effects of three tillage systems and three PAM concentration on sediment loss, runoff nitrate concentration, nitrogen losses from the soil-plant system and nitrogen recovery. The experimental design was a randomized complete block with split-plot arranged in three replications. The anionic polyacrylamide (PAM) were in three levels of zero (P0), 10 (P10) and 20 (P20) mg L-1 as the main plot and different tillage intensities as the subplot including moldboard plowing plus two disk harrow passes (CT1), one stubble cultivator pass (RT) and moldboard plowing plus one power harrow pass (CT2). The RT treatment relative to CT2 led to soil loss reduction by 23.56% during the first irrigation. The P10 and P20 treatments relative to P0, caused sediment concentration reduction by 98.1 and 98.09% and soil loss reduction by 98.7% and 98.8%, respectively. The RT × P20 treatment had a greater impact in reduction runoff nitrate losses than CT1 × P20 and CT2 × P20 treatments. Losses of N in the fertilized plots and recovery of applied N (RAN) was influenced by both tillage system and PAM application. Key words: Tillage, polyacrylamide, polyacrylamide, soil losses, nitrate.