The effects of straw mulching combined with nitrogen applications on the root distributions and nitrogen utilization efficiency of summer maize.

To provide an appropriate tillage fertilization model for improving N utilization efficiency and increasing production, the field experiments were conducted to study the effects on root distributions and N utilization efficiency of summer maize involving different straw mulching modes combined with N fertilization. No (N0), low (N1), medium (N2), and high (N3) levels of N fertilization were incorporated into soil combined with the surface coverage straw (Treatment B) and the deeply buried straw (Treatment S). The traditional cultivation was used as control treatment. The results shown that treatments S had significantly promoted deep root growth, and the root length density (RLD) increased with increases in N application rate. SN2 and SN3 treatments' average RLD were significantly increased by 67.5% and 68.1% in the greater than 40 cm soil layers. While the Treatment B had significantly increased the RLD in 0 -30 cm soil layers only. With increases in N application rate, the effect on summer maize yields increase under Treatment B were not significantly, and only BN3 increased by 0.4%, while under Treatments S were found to first increase, and then decrease. The apparent recovery efficiency of applied N, N uptake and summer maize yield of SN2 had increased by 66.8%, 20.4%, and 9.3%. Therefore the rational tillage fertilization model was deeply buried straw combined with medium N fertilizer in Hetao Irrigation District.