Nitrogen Fertilizer Recommendation Model Based On SPAD Of Leaves For Drip-irrigated Spring Wheat

【objective】 There has been widespread concern by used chlorophyll meter(SPAD-502) to content plant nitrogen nutrition. Drip irrigation used by spring wheat in XinJiang, Topdressing frequency increased significantly, to grasp the accurate number of the time for each application become more and more difficult. So that may be administered with the water according to the nutritional status of wheat Nitrogen fertilizer. Therefore the establishment of drip irrigation in spring wheat Nitrogen Fertilizer Recommendation Model Based on SPAD blade is necessary. This model provides a reference in scientific nitrogen management for us to accurately, quickly and easily determine the condition of nitrogen abundance or deficiency. 【method】 With XinChun 6 and XinChun 35 as research materials, a field plot experiment was carried out in six nitrogen treatments, respectively 0, 75, 150, 225, 300, 375kg/hm2. Logistic equation regression analysis were applied to study nitrogen absorption law under different nitrogen levels; the conventional fertilizer proportion of nitrogen was evaluated using nitrogen nutrition index; a SPAD chlorophyll meter was used for the determination of leaf SPAD values. In combination with plant testing technology, an installment recommendation model of nitrogen fertilizer could finally be built and verified 【results】(1) Nitrogen nutrition index at various stages of both varieties showed that both the suitable nitrogen rate was in 225 ~ 300 kg/hm2. The nitrogen demand of XinChun 35 with a longer growth period was greater than that of XinChun 6. Nitrogen ratio manifested as a higher base fertilizer rate and a relative lack rate of in mid. The nitrogen application rate seemed insufficient for XinChun 6 in premetaphase stage while in mid and late for XinChun 35 in particular.(2) An extremely significant linear correlation was showed between SPAD values and nitrogen levels, leaf N content while a secondary significantly correlation between SPAD values and yields in jointing stage, booting stage, heading and flowering and milky ripe stage.(3) The critical measures to diagnose nitrogen nutrition using SPAD values were 42.4, 39.4, 41.8, 54.1 respectively in jointing stage, booting stage, heading and flowering and milky ripe stage. The parameter equation for recommendation model.(4) 18 kg of fertilizer could be saved and by 4.2 fertilizer use efficiency could be promoted using the recommendation model than conventional nitrogen application. In this case, lack of nitrogen(nutrition index closer to 1) did not appear in wheat growth while the yield was the same as the conventional fertilization treatment. 【Conclusion】 An installment recommendation model of nitrogen fertilizer based on leaf SPAD values by using a SPAD chlorophyll meter to diagnose nitrogen nutrition of drip spring wheat could save fertilizer and promote the fertilizer use efficiency under the premise of the normal nitrogen supply and yield of wheat. Therefore, a recommendation model could be built to guide nitrogen application by installments.