The Effect Of Nitrogen Fertilizer Treatments On The Grain Yield And Root Traits Of Indica Rice Varieties With Different Nitrogen Uptake Efficiency

To make clear the basic characteristics of high amount of nitrogen absorption(ANA) types and its response to nitrogen fertilizer treatments, a total of15conventional indica rice varieties were potted-cultured under different nitrogen fertilizer treatments in2011and2012, respectively. The root morphology, root activity, leaf area, grain yield and yield components, dry matter weight, nitrogen ratio were measured. Based on amount of nitrogen absorption(ANA) by cluster method, these rice varieties were clustered into3types for high ANA types, middle ANA types and low ANA types. The differences of grain yield and yield components, source-sink, dry matter production and distribution, nitrogen absorption and utilization, root traits among different ANA types were analyzed. The main results were as follows:1、The range of ANA at the mature stage of indica rice varieties were0.123～0.195(Non-N level),0.612～0.807(Low-N level),0.59～1.246(Middle-N level),0.794～1.444(High-N level), and0.304～0.422(base fertilizer),0.478～0.628(base-base fertilizer),0.398～0.564(base-tillering fertilizer),0.483～0.655(base-promote spikelets fertilizer),0.429～0.660g/plant(base-protect spikelets fertilizer). There was a significant difference among varieties and treatments on amount of nitrogen absorption (ANA). With the increasing of nitrogen rate, the ANA added among indica rice varieties with different ANA. Under the condition of Middle-N level, the growth of high ANA types was the largest. To further increased the nitrogen rate, the growth of high ANA types were lower than the middle ANA and low ANA types. To the fertilizer application period, the ANA in a descending order as:base-base fertilizer, base-promote spikelets fertilizer, base-protect spikelets fertilizer, base-tillering fertilizer and base fertilizer. Compared with base fertilizer, the growth of ANA showed base-base fertilizer>base-tillering fertilizer, base-promote spikelets fertilizer>base-protect spikelets fertilizer, this result explained that applicating fertilizer earlier was good for adding amount of nitrogen absorption.2、Great differences on grain yield were observed among different ANA types and nitrogen fertilizer. The grain yield of high ANA types were higher than that of middle ANA types and low ANA types. The ANA and grain yield had significant linear positive correlation. With the increasing of nitrogen rate, the grain yield added correspondingly of different ANA types, and the grain yield of high ANA types in Low-N and Middle-N levels were higher than that of low ANA types in High-N levels. Add nitrogen to the Middle-N levels, the grain yield of high ANA types increased by a big margin. Other cases, particularly nitrogen fertilization to High-N levels, the rate of high ANA types were significantly smaller. To the fertilizer application period, the grain yield in a descending order as:base-promote spikelets fertilizer, base-base fertilizer, base-protect spikelets fertilizer, base-tillering fertilizer and base fertilizer. Compared with base fertilizer, the growth of yield showed base-base fertilizer>base-tillering fertilizer, base-promote spikelets fertilizer>base-protect spikelets fertilizer, this result explained that applicating fertilizer earlier was good for adding grain yield.With the type of nitrogen uptake increased, spikelets declining,1000-grain weight showed an upward trend, the number of spikelets per panicle, seed setting rate trends were mixed. Under nitrogen treatments,1000-grain weight among different ANA types and spikelets between treatments had significant differences. Under nitrogen period treatments, spikelets, the number of spikelets per panicle,1000-grain weight among different ANA types and spikelets between treatments had significant differences. The high ANA types showed smaller spikelets, lager the number of spikelets per panicle, medium to high seed setting rate and lager1000-grain weight. Adding nitrogen fertilizer was benefit to increase the spikelets and1000-grain weight of different ANA types, but in the case of High-N levels,1000-grain weight decreased, the number of spikelets per panicle and seed setting rate increased first and then decreased. Increasing the base-tillering fertilizer was benefit to add spikelets, while panicle fertilizer was good for increasing the panicles.3、The high ANA types had lager leaf area at heading and maturity stage, greater sink capacity, and smaller specific leaf weight. Amount of nitrogen was in favor of increasing the leaf area and sink capacity of the high ANA types. Increased panicle fertilizer, particularly base-promote spikelets fertilizer can improve the leaf area and sink capacity.4、Dry matter accumulation of the high ANA types at heading and maturity stage were higher than those of the middle ANA and low ANA types, while its economic coefficient was smaller. Great differences on dry matter accumulation were observed among types and treatments, but there was no significant difference in economic coefficient. It is benefit to promote dry matter accumulation at heading and maturity stage by increasing the nitrogen fertilizer, but the economic coefficient reduced. Base-promote spikelets and base-base fertilizer which can be more in favor of promoting dry matter accumulation at each stage.5、In various nitrogen treatments, the amount of nitrogen absorption at heading and maturity stage was lager with the types which had the higher nitrogen absorption capacity. There was a significant difference in nitrogen absorption among types and treatments. With the amount of nitrogen increased, the amount of nitrogen absorption at heading and maturity stage were significantly increased. Base-promote spikelets and base-base fertilizer which can be more in favor of promoting the amount of nitrogen absorption.In most nitrogen treatments, the nitrogen uptake and utilization efficiency, nitrogen physiological efficiency, nitrogen agronomic efficiency and nitrogen partial productivity of the high ANA types were lager than the middle ANA and low ANA types, but the differences were smaller on the harvest index. With the nitrogen fertilizer increased, the nitrogen uptake and utilization efficiency, nitrogen physiological efficiency, nitrogen agronomic efficiency, nitrogen partial productivity and harvest index of every ANA showed a downward trend. In most cases, it is good for improving the nitrogen uptake and utilization efficiency, nitrogen physiological efficiency, nitrogen agronomic efficiency and nitrogen partial productivity by adding the base-promote spikelets and base-base fertilizer.6、In the same amount of nitrogen treatments, the number of adventitious roots per plant and root dry weight per plant with high amount of nitrogen absorption was significantly superior to those with middle and low amount of nitrogen absorption, the maximum length of adventitious roots per plant was largest or near maximum. The root activity per plant of the high ANA types were larger in Middle-N and High-N levels, and the total or active absorption area per plant had certain advantages in Low-N levels, the ratio of shoot to root(at heading and maturity stage) was smaller in most nitrogen treatments. the number of adventitious roots per panicle, maximum length of adventitious roots per panicle and root dry weight per panicle of high ANA types were significantly superior to those of middle and low ANA types. There was a significant difference on most root traits among varieties types. It is benefit to promote the ratio of shoot to root of every ANA types by adding nitrogen fertilizer as well as be good for the plant root activity and maximum length of adventitious roots per plant of high ANA types. Amount of nitrogen was conducive to add the number of adventitious roots per plant, root dry weight. It was benefit to promote the occurrence of adventitious roots and elongation with early nitrogen, while the latter nitrogen was in favor of improving adventitious root enrichment and physiological traits.Correlation analysis indicated that the ANA of maturity stage was associated with the number of adventitious roots, maximum length of adventitious roots, root activity per plant and the heading ratio of shoot to root showed significant or extremely significant positive linear correlation, the root dry weight per plant of high ANA types and the ANA showed a significant linear correlation relationship. Combined with correlation analysis and path analysis, the results showed that the heading ratio of shoot to root, number of adventitious roots, root activity, maximum length of adventitious roots and root dry weight per plant was the primary root traits which can affect the nitrogen absorption capacity to the high ANA types.