Bentonite clay with different nitrogen sources can effectively reduce nitrate leaching from sandy soil

Nitrate (NO(3)(-1)) leaching from soils results in the lower soil fertility, reduced crop productivity and increased water pollution. The effects of bentonite clay mixed with various nitrogen (N) fertilizers on NO(3)(-1) leaching from sandy soils haven’t been extensively studied. Therefore, the present lysimetric study determined NO(3)(-1) leaching from bentonite [0, 2 and 4% (m/m)] treated sandy soil under three N sources (calcium nitrate [Ca(NO(3))(2)], ammonium chloride [NH(4)Cl], and urea [CO(NH(2))(2)] at the rate of 300 kg N ha(-1)). Results showed that bentonite markedly reduced NO(3)(-1) release in the leachate, while 4% bentonite retained higher NO(3) in the soil. The NO(3)(-1) leaching from sandy soil varied with N sources as Ca(NO(3))(2) > NH(4)Cl > (CO(NH(2))(2). At early stages of leaching, higher concentrations of NO(3)(-1) were detected in leachate with both NH(4)Cl and Ca(NO(3))(2), but leaching of NO(3)(-1) increased with urea at later leaching stages. The amount of total NO(3)(-1) retained in soil was conversely related to the amount of NO(3)(-1) in the leachate. This study indicated that soil amendment with bentonite could efficiently mitigate NO(3)(-1) leaching from sandy soil and hence prevent N fertilizer losses and groundwater pollution.