Effects of nitrogen application on yield, photosynthetic characteristics and water use efficiency of hybrid millet

【Objectives】 The rational fertilization schedule has being required by the steadly increasing of yield of hybrid millet and intensive cultivation technique. A field experiment was conducted to study the influence of nitrogen application rate on biomass, yield, photosynthetic characteristics and water use efficiency (WUE) of hybrid millet for determining the rational nitrogen application scheme. 【Methods】The field experiment was conducted with Zhangzagu No. 5 hybrid millet as research object. The study consisted of 6 nitrogen application rates, 0, 100, 200, 300 kg/ha (application for three times), 300 kg/ha (application for two times) and 400 kg/ha with the treatments code from N0 to N5 continuously. 【Results】The yield, photosynthetic characteristics and water use efficiency of millet are significantly related to nitrogen application levels. The hybrid millet biomass in the nitrogen application treatments are increased by 26.33%-87.21% than that in the control treatment (N0), and the variation of biomass in different treatments was significant. The higher millet grain yields are in the N3 (300 kg/ha) and N5 (400 kg/ha) treatments, which are 8202 kg/ha and 8537 kg/ha respectively, and the difference between N3 and N5 is not significant. The variation tendency of water consumption is different at the growing stages of millet. At the early growing stages the water consumption of hybrid millet is not changed significantly, and the maximum daily water consumptions are in the N0 treatment at the jointing and heading stages. The largest daily water consumption is in the N3 treatment at the late growth stage. The variation of total water consumption in whole growing period of millet is relatively small，the largest total water consumption is in the N1 treatment. The smallest net photosynthetic rates (Pn), transpiration rates (E) and stomatal conductances (C) of hybrid millet are separately in the N0 and and the largest in N3 treatments. The highest water use efficiencies of yield (WUE), of dry matter (WUEDM) and of single-leaf (WUESL) are all in the N3 treatment. Under the highest nitrogen application amount, 400 kg/ha (N5), the highest yield of millet is obtained, while the water use efficiency is lower than that in the N3 treatment. 【Conclusions】 The rational use of nitrogen increases Pn, E and C of hybrid millet and coordinates the relationships between the water and nitrogen, improves the water use efficiency. The same amount of nitrogen application the yields and WUEs are significantly different when the fertilization are applied different periods. The larger amount of nitrogen application at the earlier growing period of millet decreases the nutrients translocation to grains, and has low yield. N 300 kg/ha (application for three times) is proposed as the rational amount of nitrogen application for higher yield of hybrid millet in the region.