Nitrogen is an important component of protein, nucleic acid, chlorophyll and some hormones in plants, and it is also an important factor limiting plant growth and yield formation. Therefore, nitrogen is one of the main elements for crop growth, yield formation and quality. Soybean is one of the important crops in China, and it is favored by the public because it is rich in protein. Soybean has the function of nitrogen fixation, so the application of nitrogen fertilizer will have a great impact on yield and quality. The research progress on the effects of nitrogen fertilizer on soybean yield, quality and related physiological indexes was introduced, which provided theoretical data support for rational application of nitrogen fertilizer and improvement of soybean yield and quality.
I. Outputs
At present, there are many studies on the effect of nitrogen fertilizer on yield in China, and a lot of detailed studies have been carried out on different varieties, different fertilization periods and different application rates. Du Tianqing [1] and others reported that with the increase of nitrogen application rate, the inhibition of nitrogen fertilizer on soybean nodule formation in raw land increased, but it promoted the growth of soybean root system in the later stage. The application of nitrogen fertilizer increased the leaf area index and dry matter accumulation in the whole growth period, improved the yield components and increased the yield. Chen Hu et al. [2] studied the yield performance of hybrid soybean miscellaneous oil beans 1 under different nitrogen fertilizer levels. The results showed that adding nitrogen fertilizer could significantly increase the yield of hybrid soybean and give full play to its yield potential. Zhang Yong [3] and others used the soybean variety Fengshou 24 as the experimental material, and carried out experiments of foliar nitrogen spraying at pod setting stage and filling stage respectively. The results showed that the effect of foliar spraying nitrogen fertilizer on the yield of Fengshou 24 reached a very significant level. The higher the concentration of nitrogen fertilizer, the better, and the yield of 2% concentration treatment was the highest. Tian Yanhong [4] and others believe that reducing the application of nitrogen fertilizer as base fertilizer is helpful to reduce the growth inhibition of nodules, delay the decline of soybean roots and nodules in the later growth stage, and promote the accumulation of nutrients and dry matter. The effect of topdressing nitrogen fertilizer at the initial stage of grain filling is more significant than that of one-time application, but the effect of topdressing nitrogen fertilizer at flowering, pod setting and grain filling stage is not significant. Zhang Weilong et al. [5] used male sterile lines and their homotypic maintainers as materials to study the effects of different nitrogen topdressing rates at the initial flowering stage on the seed setting rate of soybean seed production female parents. It is considered that topdressing nitrogen fertilizer has different effects on the seed setting rate of female parents with different outcrossing rates. Different topdressing nitrogen fertilizer has little effect on the pod setting number of soybean fathers, but it has important effects on the pod setting number and seed setting rate of female parents. Wang Xueyi et al. [6] reported that the application of nitrogen fertilizer in meadow chernozem had significant effects on soybean yield and quality, and the effects on different varieties were different. Increasing nitrogen application is helpful to improve the yield of late-maturing and early-maturing varieties and reduce the yield of middle-maturing varieties. Song Xiqing et al. [7] used high protein variety Heinong 43 and high fat variety Heinong 4 1 as experimental materials to study the effects of nitrogen fertilizer on the yield of different types of soybeans. The results showed that the effect of nitrogen fertilizer on protein content of high-oil varieties was higher than that of high-protein varieties. The effect of nitrogen fertilizer on soybean yield and protein content reached a significant level, and this effect varied with varieties. The protein content of high-protein varieties and high-oil varieties showed a parabolic trend with the change of nitrogen fertilizer. Mu et al. [8] reported that the effects of increasing nitrogen fertilizer on different types of varieties were different. The yield of the varieties with the second limited pod-setting habit depends on the top pod, and they prefer to fertilize water without removing fertilizer in the later stage, so the yield will be higher, while the varieties with the unlimited pod-setting habit rely on branches to increase the yield. The higher the amount of fertilization, the more vigorous the plant growth, the less pods and the lower the yield.
Second, quality.
In terms of the effect of nitrogen fertilizer on soybean quality, there are many studies on protein and fat content of soybean by applying nitrogen fertilizer to different types of soybean in different periods. For example, Liu Bo et al [9] used high-oil soybean varieties and high-protein soybean varieties as experimental materials and applied nitrogen at the end of branching. The results showed that proper application of nitrogen fertilizer could increase the content of crude fat, decrease the content of oleic acid, linolenic acid and increase the content of linoleic acid. Song Xiqing and other research results prove that the effect of nitrogen fertilizer on protein content of high-oil soybean is higher than that of high-protein soybean. Zhang Yong et al. reported that the fat content of soybean decreased with the increase of nitrogen fertilizer concentration when nitrogen fertilizer was sprayed at pod setting stage and grain filling stage. However, the content of protein and the total amount of egg fat are rising.
Third, physiological characteristics.
At present, the reports on the effect of nitrogen fertilizer on soybean in China are not only limited to yield and quality, but also include reports on physiological characteristics such as leaf area index, photosynthetic characteristics, number of nodules and root activity. Li Ni et al. [10] thought that nitrogen application improved the nitrogen nutrition status of plants, delayed the senescence of leaves and roots in the later stage to some extent, promoted the growth of leaves in the early stage, and maintained a high leaf area index during the whole growth period, thus promoting the accumulation of dry matter and its distribution to pods, increasing the number of pods per plant, the number of grains, the weight of 100 grains and the grain yield. In the early flowering stage, paying attention to the application of nitrogen fertilizer in the later growth stage can strengthen the source expansion sink and further increase the yield. Cai Yan [1 1] and others think that appropriate nitrogen application rate and high nitrogen treatment can coordinate the distribution of dry matter in different parts of soybean at the late growth stage and improve soybean yield; High nitrogen treatment promoted the accumulation of dry matter in stems and leaves at the late growth stage, but the distribution rate of dry matter to pods was low, which led to the decrease of yield. Gu Qiurong et al. [1 1] studied the effects of different fertilization types on photosynthetic characteristics of soybean leaves under field conditions. The results showed that compared with the control, the photosynthetic rate, stomatal conductance, intercellular CO2 concentration, chlorophyll content and yield at maturity of the three fertilization treatments were improved to varying degrees. It is considered that the application of ammonium nitrogen fertilizer can increase the chlorophyll content of soybean leaves, improve the photosynthetic characteristics of soybean leaves, promote soybean growth, optimize yield composition and increase soybean yield. Dong Shoukun et al. [13] reported that under the condition of straw returning, the organic matter content in albic soil was positively correlated with the total nitrogen content, the organic matter content was positively correlated with the alkali-hydrolyzable nitrogen content, and the alkali-hydrolyzable nitrogen content was positively correlated with the total nitrogen content. Yan Jun et al [14] studied the effects of different forms of nitrogen in biological nitrogen fixation on root biomass, root-shoot ratio, root morphology and phosphorus efficiency of soybean at different growth stages. It is found that root biomass and root morphological characteristics (root length, root volume, root surface area and root tip number, etc.) are closely related to root growth. ) and phosphorus were higher than CK, but the root-shoot ratio, average diameter and phosphorus utilization efficiency were lower than CK. Zhang Wu et al. [15] thought that the application of rhizobia in a certain range of nitrogen application could obviously increase the air-dry weight of soybean nodules, promote pod setting and grain bulging, and the yield increase was obvious. Zhang Jianxin et al [16] reported that different nitrogen application levels had great influence on the vertical distribution of pods per plant, seeds, cavities and seed setting rate of soybeans with different pod-setting habits. Nitrogen application has little effect on the distribution of pod number and has no effect on the seed setting rate per plant; Nitrogen application significantly increased the internode length by 5- 13 and the basal internode thickness. Appropriate amount of nitrogen fertilizer mainly improved the pod-setting ability of the upper part of soybean population, thus increasing the total pod cavity number and total grain number. Shen Xiaohui et al [17] studied the spectral reflectance and chlorophyll content of soybean leaves at different growth stages and different nitrogen application levels, and considered that the spectral reflectance of soybean leaves without nitrogen application was higher than that of soybean leaves with nitrogen application. With the increase of nitrogen application rate, the spectral reflectance of soybean leaves decreased, and it was preliminarily considered that pod-setting stage was a sensitive period for soybean nitrogen spectral nutrition diagnosis, and chlorophyll content increased with the increase of nitrogen application rate.
Four. abstract
Nitrogen affects the leaf area index, photosynthetic utilization rate, root activity and nodule number of soybean, and then affects the yield components of soybean. Different types of soybean have different protein and fatty acid contents. Therefore, the rational application of nitrogen fertilizer has an important influence on the yield and quality of soybean, and the type and application period of nitrogen fertilizer have a great influence on the growth and development of soybean nodules and aboveground parts. Therefore, when applying nitrogen fertilizer, we should pay attention to the selection of high-efficiency nitrogen fertilizer according to different varieties, determine the best concentration, and pay attention to the flowering and pod-setting period.