Effects of Mulching and Nitrogen on Soil Nitrate-N Distribution, Leaching and Nitrogen Use Efficiency of Maize (Zea mays L.)

Mulching and nitrogen are critical drivers of crop production for smallholders of the Loess Plateau in China. The purpose of this study was to investigate the effect of mulching and nitrogen fertilizer on the soil water content, soil nitrate-N content and vertical distribution in maize root-zone. The experiment was conducted over two consecutive years and used randomly assigned field plots with three replicates. The six treatments consisted of no fertilizer without plastic film (CK), plastic film mulching with no basal fertilizer and no top dressing (MN(0)), basal fertilizer with no top dressing and no mulching (BN(1)), plastic film mulching and basal fertilizer with no top dressing (MN(1)), basal fertilizer and top dressing with no mulching (BN(2)) and plastic film mulching with basal fertilizer and top dressing (MN(2)). In the top soil layers, the soil water content was a little high in the plastic film mulching than that without mulching. The mean soil water content from 0 to 40 cm without mulching were 3.35% lower than those measured in the corresponding mulching treatments in 31 days after sowing in 2012. The mulching treatment increased the soil nitrate-N content was observed in the 0–40-cm soil layers. The results indicate that high contents of soil nitrate-N were mainly distributed at 0–20-cm at 31 days after sowing in 2012, and the soil nitrate-N concentration in the MN(2) treatment was 1.58 times higher than that did not receive fertilizer. The MN(2) treatment greatly increased the soil nitrate-N content in the upper layer of soil (0–40-cm), and the mean soil nitrate-N content was increased nearly 50 mg kg(−1) at 105 days after sowing compared with CK treatment in 2012. The soil nitrate-N leaching amount in MN(1) treatment was 28.61% and 39.14% lower than BN(1) treatment, and the mulch effect attained to 42.55% and 65.27% in MN(2) lower than BN(2) in both years. The yield increased with an increase in the basal fertilizer, top dressing and plastic film mulching, and the grain yield increase ranged from 31.41% to 83.61% in two consecutive years. The MN(1) and MN(2) treatment is recommended because it increased the grain yield and improved the fertilizer use efficiency, compared with the no-mulching treatment.