Effects of tillage practices on nitrogen accumulation and translocation in winter wheat and NO₃^--N content in soil

Conservation tillage practices, including notillage, rotary tillage, subsoil tillage and so on, are applied widely for wheat (Triticum aestivum) production in Northern China. They are primarily used because of their positive effects on soil fertility, water conservation and crop yield. Tillage practices affect not only soil properties and grain yield but also plant nitrogen metabolism. To determine the effects of tillage practices on nitrogen accumulation, distribution, translocation and soil NO3- -N content, a field experiment was carried out on high fertility soil with organic matter 14.5 g/kg, alkalihydrolysable N 106.8 mg/kg, available P 35.2 mg/kg and available K 116.9 mg/kg in Shijiawangzi village, Yanzhou city, Shandong province, China, using the wheat cultivar, Jimai 22, which has high yield and medium gluten potential. There were five treatments, strip rotary tillage (SR), strip rotary tillage after subsoiling (SRS), rotary tillage (R), rotary tillage after subsoiling (RS) and plowing tillage (P). There were three replicates for each treatment. The plot area was 4 m4 m and a 2 m wide protective belt was left between every two adjacent experimental plots. The basic seedling number was 180 plant/m2. The results indicate that the soil moisture contents of SRS and RS treatments in 20-140 cm layers are lower than those of the SR and R treatments from the anthesis to the maturity, respectively. The nitrogen uptake intensities after the jointing, nitrogen accumulation amounts in plant at the anthesis and the maturity, nitrogen distribution proportions in grain at the maturity and the nitrogen translocation amounts from vegetative organs to grain after the anthesis are higher in SRS and RS treatments than those in SR and R treatments. The nitrogen distribution amounts in grain at the maturity are the highest in SRS and RS treatments, and followed by P treatments which is higher than those in SR and R treatments. The soil NO3- -N contents in 0-80 cm soil layers in SRS and RS treatments are lower than that in P treatment, and the contents in SR and R treatments are higher than that in P treatment, in which the content in SR treatment is the highest. The soil NO3- -N content in 120-160 cm soil layer of RS is higher than those of the others, and there are no significant differences of the contents in 160-200 cm soil layers among the five treatments. The SRS and RS treatments gain the highest grain yields and nitrogen partial factor productivity which have no significant differences between them, and then the P treatment, followed by R and SR treatments. Based on a comprehensive consideration of nitrogen use efficiency, grain yield and soil NO3- -N content, we recommend that the SRS is the most appropriate tillage practice in high yield and benefit production of wheat in Northern China.