Drip irrigation lateral spacing and mulching affects the wetting pattern, shoot-root regulation, and yield of maize in a sand-layered soil

Soil with a 20-60 cm thick subsoil (60-90 cm below the surface) sand layer has been recently reclaimed to exploit its grain production potential in an arid region in northwest China. A 2-year field study was conducted in the Hetao irrigation district to investigate the effects of lateral spacing and soil mulching methods under drip irrigation on the soil moisture, NO3-, shoot-root regulation, and water use efficiency (WUE) of spring maize. The Christiansen uniformity coefficient (C-us) was adopted to evaluate soil moisture and NO3- distribution, which was calculated with soil water content and NO3- concentration. The four studied treatments consisted of two irrigation lateral-spacings (Al: 1.0 m, A2: 0.5 m) and two film-covering modes (Ml: fully mulched, M2: partially mulched) were arranged. Soil moisture was most affected by mulch coverage (full or half surface coverage) under low frequency irrigation lateral spacing (adjacent to or between crop rows) under high frequency irrigation. Lateral spacing exerted a notable influence on soil moisture at a 20 cm depth, while the mulching method influenced soil moisture mainly at 40 cm. Irrigation frequency and close lateral spacing can effectively enhance C-us. Based on our observations, a decrease in the C-us of soil NO3- may occur under frequent fertigation, particularly when irrigation laterals are between crop rows. The mulching method can play an important role in improving the concentration and C-us of soil NO3-, while the A2 treatments can slow the decrease of the C-us of soil NO3- under frequent fertigation. Root length density (RLD) under Al treatments were lower close to lateral while higher away from lateral than A2 treatments. Close lateral spacing can result in high hundred gain weight (HGW) and high harvest index (HI) while exerting a more conspicuous effect than the mulching method by extending the grain filling stage. Frequent fertigation (i.e. once every three days) after jointing is preferentially recommended in a sand layered field. Al M2 should be chosen for higher HI and low cost. If frequent fertigation is infeasible, A2M1 can be a good choice under low frequency fertigation. (C) 2017 Published by Elsevier B.V.