| The experiment was carried out in the off-campus experimental base of Maba Town,Xuyi County,Huai ’an City,Jiangsu Province from 2019 to 2020.Under the Rice and shrimp continuous cropping,the mid-maturing mid-japonica rice varieties Nanjing 5718 and Tianlongjing 6,which are mainly promoted in the local area,were used as materials.The split-zone design was adopted,with nitrogen fertilizer amount(N)as the main zone and pot seedling planting density(D)as the split-zone design.The fertilizer was mixed with team controlled-release nitrogen fertilizer and quick-acting nitrogen fertilizer,which was applied at one time.The total applied pure nitrogen amount was 0 kg hm-2(NO)、120 kg hm-2(N1)、180 kg hm-2(N2)和 240 kg hm-2(N3)respectively.Transplanting technology was used to simulate the width and narrow rows of pot seedlings(33/23cm),and the plant spacing specifications were 17.9 cm(D1),15.5 cm(D2)and 12.4 cm(D3)respectively.The local representative high-yield urea application scheme was adopted as the control.The nitrogen fertilizer operation was carried out according to the ratio of base fertilizer:tillering fertilizer:spike fertilizer=3:3:4,and the total pure nitrogen application amount was 240 kg hm-2,In this experiment,the effects of the formula amount of controlled mixing nitrogen fertilizer and the planting density of pot seedlings on rice yield characteristics,nitrogen absorption and utilization characteristics and rice quality were systematically studied,so as to explore the suitable combination of formula amount of controlled mixing nitrogen fertilizer and planting density of pot seedlings in Rice and shrimp continuous cropping,and provide data support for high-quality and high-yield cultivation techniques of rice in Rice and shrimp continuous cropping.The main research results are as follows:The yield of the two varieties increased with the increase of formula dosage of controlled mixing nitrogen fertilizer under the same planting density of pot seedlings.The yield of Nanjing 5718 increased with the increase of planting density of pot seedlings under the same formula of controlled mixing nitrogen fertilizer,and the highest yield was 10.39～10.77 t hm-2 under N3D3 treatment,which was 2.85%～4.36%higher than CK.Tianlongjing 6 increased with the increase of planting density of pot seedlings under N1 and N2,and first increased and then decreased with the increase of planting density under N3.The highest yield appeared under N3D2 treatment,which was 10.10～10.28 t hm-2,which was 1.51%～2.09%higher than CK.Under the same transplanting density of pot seedlings,the spikelet amount of the two varieties increased with the increase of the formula amount of controlled mixing nitrogen fertilizer,while the seed setting rate and 1000-grain weight decreased.Under the same amount of nitrogen fertilizer,the spikelet amount of Nanjing 5718 population increased with the increase of transplanting density of pot seedlings.Tianlongjing 6 increased with the increase of transplanting density of pot seedlings under N1 and N2,and first increased and then decreased under N3.Compared with CK,the spikelet amount of Nanjing5718 and Tianlongjing 6 increased by 3.76%～4.55%and 1.94%～2.16%respectively under N3D3 treatment.In terms of 1000-grain weight and seed setting rate,the 1000-grain weight of the two varieties decreased with the increase of transplanting density,and the seed setting rate varied.Further analysis of yield components showed that under the same planting density of pot seedlings,the spike number per unit area and grain number per spike of the two varieties showed an upward trend with the increase of the formula amount of controlled mixing nitrogen fertilizer.Under the same amount of nitrogen fertilizer,with the increase of transplanting density of pot seedlings,the spike number per unit area of the two varieties showed an upward trend,while the grain number per spike showed a downward trend.Under the same planting density of pot seedlings,with the increase of the formula dosage of controlled mixed nitrogen fertilizer,the leaf area index and dry matter accumulation of plant population in each key growth stage of rice showed an upward trend,and the population growth rate and photosynthetic potential in each main growth stage showed an upward trend,which made the dry matter accumulation in mature stage higher,ensured the higher dry matter accumulation after heading,and was conducive to the formation of high yield.Under the same formula of controlled mixing nitrogen fertilizer,with the increase of transplanting density of pot seedlings,the leaf area index and dry matter accumulation of Nanjing5718 rice increased at each key stage,and the population growth rate and photosynthetic potential increased at each main growth stage.Tianlongjing No.6 changed the same as Nanjing5718 under N1 and N2 treatments,and each index first increased and then decreased under N3 treatment.The nitrogen content in the main growth period and the total nitrogen uptake of the two varieties increased with the increase of the formula amount of controlled mixing nitrogen fertilizer under the same planting density.Under the same formula of controlled mixing nitrogen fertilizer,with the increase of transplanting density of pot seedlings,the nitrogen content of the two varieties showed a downward trend,and the total nitrogen uptake of Nanjing 5718 showed an upward trend under all fertilizer treatments.The total nitrogen uptake of Tianlongjing No.6 showed an upward trend under N1 and N2 treatments,while the total nitrogen uptake of the plants under N3 treatment showed an upward trend at first and then a downward trend.Under the same density,with the increase of the amount of controlled mixed nitrogen fertilizer,the nitrogen accumulation in each treatment stage,the transport of plant stem sheath and leaf and the nitrogen accumulation in spike all increased.Under the same fertilization treatment,the nitrogen accumulation in plant stage increased with the increase of density.In terms of nitrogen utilization efficiency,with the increase of nitrogen fertilizer application rate,nitrogen absorption and utilization rate,nitrogen partial productivity,nitrogen physiological utilization rate and nitrogen agronomic utilization rate all showed a downward trend,while nitrogen absorption per 100 kg of grain showed an upward trend;Under the same nitrogen fertilizer treatment,with the increase of density,all nitrogen use effi ciency indexes of plants showed an upward trend,except that the nitrogen uptake of 100 kg seeds showed a downward trend.With the increase of controlled mixing nitrogen fertilizer formula and pot seedling planting density,the brown rice rate,milled rice rate and head rice showed an upward trend,and the processing quality improved;Chalky grain rate and chalkiness degree showed a downward trend,and the appearance quality became better;The content of protein in rice increased,and the nutritional quality improved.The amylose content of rice decreased,and the taste value of rice decreased,in which the hardness of rice increased,but the appearance,viscosity and balance of rice showed a downward trend,and the taste quality became worse.As for the viscosity characteristics of rice starch,the peak viscosity,hot paste viscosity,final viscosity and disintegration value all showed a downward trend,while the reduction value showed an upward trend,but there was no significant difference in gelatinization temperature.In this study,two varieties,Nanjing 5718 and Tianlongjing 6,were treated with N3D3(240kg hm-2,plant distance 12.4cm)and N3D2(240kg hm-2,plant distance 15.5cm),respectively,to obtain the highest yield.Considering rice quality and nitrogen absorption and utilization,it also has broad application prospects under N2D3(180kg hm2,plant spacing 12.4cm)treatment. |
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