| Excessive nitrogen application not only causes the waste of resources,increases theproduction cost,but also more importantly leads to a series of environmental and health problems.Therefore,study the physiological mechanism of the difference of nitrogen fertilizer utilization and nitrogen fertilizer utilization among crops has a great significance.This experiment was carried out at the Northwest Agricultural and Forestry University Agricultural Experiment Station from 2016 to 2017.The compact variety Zhengdan 958 and the semi-compact variety Zhengda 12 were used as materials.Four nitrogen fertilizer levels were set at 0?N0?kg·ha-1,150?N150?kg·ha-1,225?N225?kg·ha-1,300?N300?kg·ha-1under the field conditions,studied the difference in nitrogen use efficiency and photosynthetic physiological basis of two plant type maize varieties under different nitrogen application conditions,in order to provide theoretical guidance for scientific fertilization of maize.The main results are as follows:1.Nitrogen application had no significant effect on the ear height of the two plant types of maize,but it could effectively increase the plant height of different plant types.The height of the compact variety ZD958 increased after nitrogen application was higher than the semi-compact variety ZD12.Nitrogen application had a significant effect on the leaf angles of the two leaf types of the two plant types of maize.The difference in the response of the angles between the two layers of the two types of corn to the fertility was mainly reflected in the ear layer and the lower layer of the ear.There was no significant increase in the N225 at the 12th spike layer and the lower leaf angle of the spike in the ZD12 variety,while the compact variety ZD958 did not increase significantly at the N150.Nitrogen application can significantly increase the leaf area of??each layer of the two plant types,and the increase in the area of??ZD12 leaves is greater,but the decline in leaf area at maturity is serious,especially in the lower leaves.The compact variety ZD958 has more light energy intercepted when the nitrogen application rate is higher,avoiding the loss of light leakage;the semi-compact type ZD12 has a high nitrogen application rate(300 kg·ha-1)and can easily cause ventilation inside the canopy.The poor light transmission conditions cause premature failure of the underlying leaves.2.The leaf area index?LAI?of the two plant types showed a trend of increasing with the increase of nitrogen application rate,but the increase of the semi-compact type was greater,while the leaf area of the semi-compact type had a greater attenuation at the mature stage,especiallythe lower leaves.At the same nitrogen application rate,the LAI of the compact variety ZD958 was less than the semi-compact variety ZD12,but its leaf senescence was both slower than that of ZD958.Nitrogen application could reduce the relative chlorophyll content of the two plant type corns at late growth stage,and the effect of ZD12 was more obvious.ZD958 had a longer leaf function time than ZD12 in the later stage of fertility,and leaf senescence was slower.3.The application of nitrogen fertilizer can significantly increase the net photosynthetic rate?Pn?,transpiration rate?Tr?,and leaf water use efficiency?WUE?of the two plant types,and increase the electron transfer rate?ETR?,the actual quantum efficiency??PSII?and photochemistry of the photosystem II.The quenching coefficient?qP?effectively reduces the non-photochemical quenching coefficient?qN?and improves the potential and efficiency of corn photosynthesis.In addition to qN,the index of semi-compact corn ZD12 is higher than ZD958,a compact variety.With the increase of nitrogen application rate,the Pn,Tr,WUE and ETR,?PSII,and qP of the compact variety ZD958 showed an increasing trend;the semi-compact type ZD12 showed an increase and then decreased,and the nitrogen application amount was 225 kg·ha-1.The N225 treatment is the highest.The regularity of qN in different plant types with increasing fertility is contrary to other indicators.4.Nitrogen application can significantly increase the dry matter accumulation per plant of the two plant types.With the increase of nitrogen fertilizer,the dry matter quality of the semi-compact corn cultivar ZD12 has a greater increase,and tends to be stable when the nitrogen application amount is 225 kg·ha-1.However,the dry weight of the single plant ZD958 in the compact maize increased little,and it became stable when the nitrogen application amount was 150 kg·ha-1.With the increase of nitrogen application rate during the grain filling stage,ZD12 increased the dry matter transport rate of the stem and leaf organs to the grain,and decreased the dry matter transport rate of the high fertilizer treatment to maturity.ZD958had a higher dry matter transport rate from stems and leaves to grain at the time of silking to maturity with the increase of nitrogen application rate.The nitrogen treatment amount was higher at 150 kg·ha-1,and there was no significant difference with the increase of nitrogen application rate..5.The number of grains of the semi-compact variety ZD12 increased with increasing fertility,and there was no significant difference between the nitrogen application rates of 225and 300 kg·ha-1,and the 100-grain weight and yield both increased first and then decreased with increasing fertility.The yield was the highest when the nitrogen amount was 225 kg·ha-1.The grain number and yield of the compact variety ZD958 showed the tendency of increasing with the increase of fertility,but there was no significant difference among the fertilization treatments.When the nitrogen application amount was 150 kg·ha-1,the yield reached the highest.6.The application of nitrogen fertilizer significantly reduced the nitrogen fertilizer agronomic efficiency and nitrogen use efficiency of the two plant type corns.ZD958 applied less nitrogen fertilizer(150 kg·ha-1)can maintain a higher nitrogen fertilizer agronomy efficiency,to achieve the desired yield effect.The utilization efficiency and yield of nitrogen fertilizer of ZD12 showed that N225 treatment was the largest.The canopy structure distribution of plant individuals was reasonable and the population quality was optimal. |
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