Effect of Nitrate Leaching Caused by Swine Manure Application in Fields of the Yellow River Irrigation Zone of Ningxia, China

A five-year swine manure application trial and a study of nitrate leaching losses have been conducted. There were three treatments: traditional without manure (CK), traditional matched manure 4500 kg ha(−2) (T1) and traditional matched manure 9000 kg ha(−2) (T2). Nitrate nitrogen leaching losses at the 30-, 60-, and 90-cm soil layers were measured using the resin core method. The results indicate that the swine manure application did not noticeably increase soil nitrate leaching losses in the 30-cm layer. T1 (16.85 ± 0.40 kg ha(−2)) and T2 (17.01 °C0.46 kg ha(−2)) were not significantly different than CK (15.96 ± 0.41 kg ha(−2)) (P < 0.05), which was also the case at the 60-cm layer. However, there are significant differences between the treatments and CK at the 90-cm layer, although there were no significant differences between T1 and T2 in that layer. The application of manure can increase soil organic matter (SOM) and total nitrogen (TN). The SOM of T1 and T2 were increased to 0.95 g kg(−1) and 1.41 g kg(−1), respectively. The TN values of CK, T1 and T2 were 0.72, 0.78 and 0.88 g kg(−1), respectively, in the 0 to 30 cm layer, and were improved by 7.72% and 22.04%.