| Wheat is important in China's food crops.Jianghan Plain,located in the middle and lower Yangtze River,is one of the major wheat producing areas in Hubei Province.In the traditional cultivation methods,the amount of nitrogen fertilizer is high,and nitrogen fertilizer was mainly applied as basal,and the topdressing rate was lower or even without topdressing.In order to provide a theoretical basis for the efficient use of nitrogen in the high-yield cultivation of wheat after rice in Jianghan Plain,and to determine the most suitable nitrogen application model.The effects of nitrogen application rate and different nitrogen application on flag leaf photosynthetic characteristics,nitrogen uptake and translocation,root growth dynamics and soil nitrate nitrogen accumulation and distribution were studied in the experimental base of the Agronomy College of Yangtze University in Jingzhou,Hubei Province in 2014-2016 in wheat cultivar named Zhengmai 9023.In 2014-2015,set up 7 nitrogen treatment,with pure nitrogen 0,126,144,162,180,216kg/hm2 respectively,denote N0,N126,N144,N162,N180,N198,N216 respectively.In 2015-2016,N was topdressed before sowing,before winter,and during the jointing stage.The ratios of base-to-dressing application were 1:1:0(N1),1:0:1(N2),2:1:1(N3),1:1:1(N4),and 0:0:1(N5),under the same amount of total N(180 kg·hm-2)during the growing season.The treatment that did not use N was the control(N0),randomized block design.The main conclusions are as follows: 1.The effects of nitrogen application rate on flag leaf photosynthetic characteristics,nitrogen uptake and translocation and soil nitrate nitrogen accumulation and distribution.With the increase of nitrogen application,the SPAD value of flag leaf showed an upward trend,but when the nitrogen application rate reached 180 kg/hm2,the increasing trend was not obvious.The photosynthetic rate of flag leaf increased first and then decreased with the increase of nitrogen application rate.The Fv/Fm,qP,photochemical efficiency and ETR of wheat flag leaf photosystem? were increasing in the range of 0-180 kg / hm2.With the increase of nitrogen dry matter accumulation increased at booting stage,after anthesis the dry matter accumulation increased first and then decreased,when the amount of nitrogen is more than 180 kg/hm2,increase nitrogen has no gain effect on dry matter accumulation.With the increase of nitrogen application rate,the content of MDA in flag leaves of wheat decreased,and the effect of increasing nitrogen fertilizer on delaying the decline of MDA content in Flag Leaves of wheat was not significant when the nitrogen application rate increased to 180 kg/hm2,indicating that the appropriate amount of nitrogen can reduce the lipid peroxidation of flag leaf cell membrane,thereby delaying the senescence of leaves.The application of nitrogen fertilizer could significantly increase the nitrogen accumulation and grain protein content of wheat plants.The nitrogen transfer of vegetative organs increased with the increase of nitrogen application rate,and the accumulation of nitrogen after anthesis increased first and then decreased,and N180 was the highest.The nitrogen use efficiency and nitrogen fertilizer production efficiency of wheat showed a decreasing trend,while nitrogen uptake efficiency and nitrogen yield index increased first and then decreased with the increase of nitrogen application rate.N180 treatment was higher.The accumulation of NO3-N in 0-100 cm soil layer increased with the increase of nitrogen application rate.In anthesis the NO3-N content in soil decreased with the increase of soil depth.In the mature stage,the content of nitrate decreased with the increase of soil depth,except for N216 treatment.The soil nitrate content of N216 treatment of 60-100 cm was significantly higher than other treatment.In the range of 0-180kg/hm2,the yield increased with the increase of nitrogen application rate,and the yield was decreased when the nitrogen application rate was more than 180kg/hm2.The spike number increased with the increase of nitrogen application rate.When the nitrogen application amount was 180kg/hm2,the effect of increasing spike number was not significant.As to the number of grains per spike,with the increase of nitrogen application rate,it showed a trend of increasing and then decreasing.And the grain weight did not show obvious change with the increase of nitrogen application rate.180 kg / hm2 is the more appropriate level of nitrogen application.2.The effects of different nitrogen application on flag leaf photosynthetic characteristics,nitrogen uptake and translocation,root growth dynamics and soil nitrate nitrogen accumulation and distributionSPAD value and photosynthetic rate of N1 and N5 treatments was higher before anthesis and sharply decreased after anthesis,while the nitrogen topdressing at jointing stage can delay the decline of SPAD value and photosynthetic rate of flag leaf after anthesis.Nitrogen fertilizer as base fertilizer,before winter and jointing application,can improve the maximum photochemical efficiency(Fv/Fm),the actual photochemical efficiency(PSII)and photosynthetic activity(qP)of photosystemII,maintain a high photosynthetic activity after anthesis.Fertilization in the early stage is conducive to the transfer of dry matter,topdressing at jointing stage was beneficial to the accumulation of dry matter after anthesis.Reasonable application of nitrogen fertilizer can coordinate transfer before anthesis and accumulation after anthesis of dry matter,increased dry matter accumulation in wheat.Reasonable nitrogen fertilization(N4)could increase the amount of nitrogen accumulation after anthesis and the amount of nitrogen transferred by vegetative organs,and finally get higher grain nitrogen accumulation and increase the efficiency of nitrogen absorption and utilization.The amount of basal fertilizer was related to the accumulation of NO3-N in 100-200 cm soil layer,while the amount of topdressing was related to the accumulation of NO3-N in 100-200 cm soil layer.Therefore,the excessive application of nitrogen fertilizer at jointing stage could increase the nitrate nitrogen residue in 0-100 cm soil layer,but the high nitrogen application rate before winter could increase the soil nitrate accumulation in the 100-200 cm soil layer,which could easily lead to leaching loss,so,N4 treatment is a more appropriate nitrogen application.The root diameter to show a downward trend from the joint stage,and with the increase of soil depth the root diameter decreases.Application of nitrogen fertilizer at jointing stage could slow down the decrease of root diameter.The root length showed a trend of increase first and then decrease,and reached the maximum at anthesis stage,nitrogen application at jointing stage was favorable for the growth of root system before anthesis,and reduced the decrease of root length of wheat after anthesis.For the root numbers,except for N0 and N5,the other treatments showed the trend of rising and then decreasing,and reached the maximum value at the booting stage.The decrease in N5 and N1 treatment was much larger than that of other nitrogen fertilizers from the jointing stage to the mid-grain filling stage.The number of different depths is 20-40cm> 40-60cm> 0-20 cm,and the root number of 0-20 cm soil layer is relatively stable.The proportion of 20-40 cm and 40-60 cm was decreased,and the total number of root changes are caused by changes in the number of 20-40 cm and 40-60 cm soil layers.The reasonable nitrogen application can make the wheat yield factors reach a high level,and get high yield.Considering wheat yield,grain protein content,grain protein yield,nitrogen fertilizer uptake and utilization,and accumulation of NO3-N in 0-200 cm soil layer.N4 treatment,the ratios of base-to-dressing application were 1:1:1 under the amount of total N(180 kg·hm-2),which consideration on both economic and ecological benefits. |
PDF Full Text Request