Increasing yields while reducing soil nutrient accumulation by straw strip mulching in the dryland wheat (Triticum aestivum L.) cropping system of Northwest China

Surface mulching is an effective strategy to increase yields in rainfed agroecosystems. The plastic film residue and overuse of chemical fertilizer cause a serious non-point source pollution and high production input cost. With mulching, farmers typically attempt to maintain the balance of soil nutrients and reduce fertilizer use while ensuring high yields. Straw strip mulching (SM) is a new mulching technique, but the effects on nutrient uptake have not been studied yet. Therefore, 19 field comparative experiments were conducted in four growth seasons of winter wheat with three mulching treatments: (1) straw strip mulch (SM), a partial ground mulching using whole corn stalks that alternate with planting strips without mulch; (2) full-field plastic film mulching (PM); and (3) no mulching with wheat sown in rows, as a control (CK). Compared with CK, on average over all experiments, SM increased grain yield by 11.5%, biomass by 19.0%, the total aboveground uptakes of nitrogen (N), phosphorus (P) and potassium (K) by 16.1%, 18.4% and 22.9%. There were no significant differences between SM and CK in N and P requirements, the N, P and K concentrations in grain. The increased total aboveground uptake of each nutrient was closely associated with higher biomass, grain yield and straw yield (r = 0.66 −0.84, P < 0.01). Relative to CK, SM significantly decreased the total accumulation of residual NO3-N in the top 100 cm at maturity stage by 32.3% (22.7 kg ha-1) in typical fertilization (N, 120 kg ha-1; P2O5, 90 kg ha-1) and by 33.8% (45.8 kg ha-1) in high fertilization (N, 150 kg ha-1; P2O5, 120 kg ha-1), and the leaching of NO3-N into the deep soil below 40 cm. When only grain nutrients exported from the field after harvest in typical fertilization, N balance in SM, PM and CK accounted for 43.8%, 38.5% and 48.6% of N input, while P balance for 74.8%, 74.0% and 78.4% of P input, respectively, indicating possible saving potentials in fertilizer costs for all treatment, but the saving potential of P is much greater than that of N. Relative to PM, SM had similar the total aboveground nutrients uptake, similar to or slightly less grain yields, and higher economic benefit. SM is suitable for popularizing in a semiarid rainfed agroecosystem.