Characteristics soil nitrate nitrogen distribution, accumulation
and nitrogen balance in winter wheat field under drip fertigation

【Objectives】We studied the NO-3-N spatial distribution and accumulated principle in winter wheat farmland soil, aiming to reduce the N loses and improve the integrated efficiency of drip fertigation system.【Methods】 Urea, NH4H2PO4 and KCl mixed to make liquid fertilizer. A filed experiment was carried at in Shandong Province, adopting the methods of recharge and fertilization by measuring soil moisture during the winter wheat growth season.Four treatments including no fertilizer(N0), 94.5 kg/hm2 (N1),189 kg/hm2 (N2) and 270 kg/hm2 (N3) of N fertilizer rates were set up, the NO-3-N spatial distribution, profile accumulation and nitrogen balance were investigated.【Results】 1)After 24 h of drip irrigation, with the increased of nitrogen application, the NO-3-N in soil at the horizontal direction of water dropper aggregated from moist soil edge to water dropper downward. When the nitrogen application was 189 kg/hm2 the NO-3-N in soil that beneath water dropper and moist soil edge had no significant difference after drip fertigation. The horizontal direction around the water dropper has the best uniformity, the NO-3-N under water dropper was mostly above 60 cm, the NO-3-N in soil at the vertical direction was not concentrated at the moist soil edge. 2)After harvest, the accumulation of NO-3-N increased with nitrogen application at 0-100 cm soil layer and when nitrogen application above N 189 kg/hm2, the accumulation became larger, and the increase in 0-40 cm was higher than in other soil layers, the accumulation at 0-40 cm was respectively 66%,72%,72% and 71% in N0, N1, N2 and N3 treatment. 3)With the increased of nitrogen application, the winter wheat nitrogen uptake and grain yield was increased at first then descended, however, the amount of residue and apparent loses of NO-3-N was increasing, apparent N loses was lower when drip irrigation, the apparent loses rate of N1,N2 and N3 was 20%,17% and 16%.【Conclusions】 Through drip fertigation, the rational drip irrigation could adjust nitrate nitrogen to transfer to the root area and concentrated on the 0-40 cm soil layer, the fertilizer concentration have little impact on the depth that nitrate nitrogen transferred. The suitable amount of nitrogen fertilizer will benefit to the distribution uniformity of NO-3-N in the horizontal direction of moist soil under the water dropper to promote the absorption of N. When the N application is 189 kg/hm2, the highest grain yield and N use efficiency can be achieved, the NO-3-N in soil around root area accumulated amount was basically balanced, and could be the best drip fertigation model that be selected.