Effects Of Chemical Control Measures At Different Densities On Lodging Resistance,Yield And Quality Of Rice

The rice variety"Daohuaxiang"is prone to overturning and has poor resistance to overturning,which is a key factor limiting its yield and quality.Reasonable planting density and chemical control measures are important regulatory tools to improve the resistance of rice to overturning.In this study,With two planting densities as the main zone:D1(15 holes·m^-2,33 cm×20 cm)and D2(19 holes·m^-2,33 cm×16 cm);four chemical control measures as the secondary zones:L1（10leaves and one heart）,and L1（10 leaves and one heart）,L1（10 leaves and a heart period sprayed with low concentration of calcium cyclamate）,H1（10 leaves and a heart period sprayed with high concentration of calcium cyclamate）,L2（11 leaves and a heart period sprayed with low concentration of calcium cyclamate）,H2（11 leaves and a heart period sprayed with high concentration of calcium cyclamate）,and another:CK（control treatment,sprayed with water）,total 10 treatments.To investigate the effects of chemical control measures on rice stalk morphological characteristics,stalk mechanical properties,stalk chemical composition,dry matter and nutrient uptake,yield and quality at different densities,and to provide a theoretical basis for achieving synergistic enhancement of high yield,high quality and resistance to overturning of rice.The main research results are as follows:（1）Reasonable close planting combined with chemical control measures can optimize the physical and mechanical properties of stems,and increase lodging resistance.Under both density conditions,Reducing density can effectively shorten the length of I1（the first internode of the stem）and significantly reduce the height of the center of gravity,with a decrease of 2.42%to7.73%.Compared with CK,spraying calcium cyclamate can effectively optimize the configuration of rice plant internodes,significantly increase the outer diameter,wall thickness,cross-sectional area,stem bending resistance,and stem plumpness of I2（the second internode of the stem）,with increases of 3.61%～11.66%,5.83%～22.61%,8.18%～16.56%,10.56%～31.47%,and21.05%～45.14%,respectively;Significantly reduced I1 length,I2 length,total length of I1+I2（between the first and second internodes of the stem）,plant height,center of gravity height（excluding L1）,and lodging index,with decreases of 12.80%to 39.16%,9.12%to 17.67%,12.90%to 25.31%,2.44%to 9.31%,5.94%to 13.75%,and 10.90%to 36.41%,respectively.Under two density conditions,there was no significant difference in the effects of spraying concentration and spraying period of calcium cyclamate on rice plant height,internode configuration,I2 outer diameter,wall thickness,and cross-sectional area.Under two density conditions and combined with economic benefits,spraying low concentration of calcium cyclamate in one center on 11leaves can achieve the optimal lodging index of rice plants.（2）Reasonable dense planting combined with chemical control measures can optimize stem composition and reduce lodging risk.Under both density conditions,Reducing density can significantly increase the content of NSC（non-structural carbohydrates）and NSC/N（ratio of non-structural drainage compounds to nitrogen content）in stems,with an average increase of7.04%and 9.42%,respectively.Compared with CK,spraying calcium cyclamate can significantly reduce the N content and N/K in rice stems,with decreases of 1.11%to 6.47%,4.03%to 15.36%,and significantly increase the K content,NSC content,NSC/N,lignin and cellulose content in stems,with increases of 2.94%to 11.39%,20.73%to 36.17%,24.18%to 34.24%,2.86%to 7.18%,and 2.48%to 6.08%,respectively.Under two density conditions,there was no significant difference in the effects of the spraying concentration and spraying period of calcium cyclamate on the N content,K content,N/K and cellulose content of rice stems.Under two density conditions and combined with economic benefits,spraying low concentration of calcium cyclamate on 11leaves can achieve the optimal lignin content of the rice plant.（3）Reasonable dense planting combined with chemical control measures can effectively increase the accumulation of dry matter and nutrients.Under both density conditions,Increasing density can significantly increase the leaves during the full heading stage（with an increase of1.92%～7.45%）and reduce the dry matter accumulation of stems and leaves during the harvest stage（with a decrease of 0.94%～4.28%）.Compared with CK,spraying calcium cyclamate can significantly increase the dry matter weight of rice stem during full heading stage,dry matter weight of stem and leaf during harvest stage,N and K accumulation of stem during full heading stage,N and K accumulation of stem and leaf during harvest stage,and K accumulation of aboveground parts during harvest stage,with an average increase of 7.60%,11.17%,5.32%,11.92%,7.27%,23.44%,and 20.84%,respectively.（4）Reasonable dense planting combined with chemical control measures can increase yield and ensure quality of rice.Under both density conditions,Increasing density can significantly or extremely significantly increase the number of grains per panicle,effective panicle number,and yield of rice,with increases of 8.88%to 15.33%,16.00%to 30.20%,and 3.50%to 5.40%,respectively.It can significantly reduce the rate of polished rice,with a decrease of 0.91%to1.48%.Compared with CK,spraying calcium cyclamate significantly increased the number of grains per spike,seed setting rate,thousand grain weight,and yield,with increases of6.99%～17.69%,0.78%～4.82%,0.50%～2.92%,and 1.47%～6.56%,respectively;Under the two density conditions,the denser rice will increase the chalkiness and chalky grain rate,both of which have no adverse effects on the quality of milled rice,nutritional quality and taste quality.In summary,increasing density will increase yield but also increase the risk of lodging in rice plants.Chemical control measures will reduce the risk of lodging in rice plants while not causing damage to rice yield and quality.Taking into account rice yield,lodging resistance,and economic benefits,it is recommended to spray low concentration calcium humate at high density during the 11 leaf one heart stage.