Optimization Model of the Effects of Transplanting Density,Nitrogen and Potassium Fertilization on Yield and Quality of an Aromatic Hybrid Rice "Luyoumingzhan"

Zeqin DENG, Xianbo HUANG*, Mingdian RAO, Chengbao LIN, Jiangxia TANG, Meijuan LIN,Shuijin LIANG

1． Sanming Academy of Agricultural Sciences，Shaxian 365051, China;

2． Fujian Liusan Seeds Company Limited, Shaxian 365500, China

Luyoumingzhan, developed by Sanming Academy of Agriculture Sciences, is a new highyield and high-quality hybrid rice taking Luxiang 618A, bred by Sichuan Academy of Agricultural Sciences, as a female parent and the restorer line Shuangkangmingzhan, bred by Sanming Academy of Agricultural Sciences as a male parent.During 2010-2011, regional tests were conducted with Luyoumingzhan in Honghe Hani and Yi Autonomous Prefecture and the results showed that average yield reached 10 894.5 kg/hm2, which increased by 6.8%compared with II You 838 in control group. In 2011, the average yield was 11 467.5 kg/hm2and its whole growing period was about 162 d.It is moderately tolerant against white leaf blight and tolerant to rice blast. In 2011, the variety was approved by Honghe Crop Variety Committee in Yunnan Province. During 2010-2011, regional tests were carried out with Luyoumingzhan in Fujian late-maturing in late rice group, and the results showed that average yield of the two years was 7 058.1 kg/hm2,which increased by 6.44% compared with control group; in 2012, the yield averaged 8 075.55 kg/hm2, increasing by 6.48%compared with Guyou 527 in control group.The whole growth period was about 127 d, the variety matured earlier(1 d)than the control variety; it was tolerant to rice blast; rice quality met grade-2 highly-qualified rice standard.In 2013,it was approved by Fujian Crop Variety Committee.

It is known that yield and quality of rice are mainly determined by genetic characteristics, as well as eco-environment and cultivation[1-3]. Currently,many researches focus on effects of variety types, fertilizer quantity, transplanting age, and cultivation density,using one or multiple factors on yield and yield components, but less attention is paid to the effects of treatmentconditions with multiple factors on rice yield and quality. Therefore, based on researches available,the test explored the effects of density,K fertilizer and N fertilizer on yield and quality of rice with Luyoumingzhan, and an optimization model will be established in order to select the optimal treatment with three cultivation factors and to provide references for high-yield cultivation of the variety.

Materials and Methods

Test design

As shown in Table 1, planting density, K fertilizer and N fertilizer were taken as test factors and yield and quality of rice contributed to an objective function, as per optimal design[4-6]and 311-A scheme.The practical scheme was shown in Table 2.Additionally, there were 22 test regions,with twice repetitions and every test region(S)was 13.34 m2.

Testing

The test site was situated in Zhuyuan Village, Qiujiang Street Office, Shaxian County, Fujian Province.The soil fertility was moderate, and soils contain organic matter at 39.5 g/kg, hydrolyzable nitrogen at 182 mg/kg, available P at 17.7 mg/kg, and available K at 34 mg/kg. Plastic films were used to divide different test regions in case of fertilizers or water accumulation.On May 18,the variety was sown, transplanted on June 18, and matured during September 26-30.

In general, the variety was fertilized with superphosphate at 375 kg/hm2; N fertilizer was applied with ratio m(base fertilizer)∶m(tillering fertilizer)∶m(earing fertilizer)at 4∶4∶2;P and K fertilizers were applied as per m(base fertilizer)∶m (tillering fertilizer)at 5∶5. Tillering fertilizer was applied 7-8 d after rice transplanting and earing fertilizer applied during the 2nd-3rddifferentiation period of young ears. In addition, disease or pest damages should be controlled, including rice blast, banded sclerotial blight, and striped rice borer.

Measurements

At maturing, effective ears from 30 rice patches and 5 typical patches were collected for exploring rice.In different test regions, moist grains were cut and weighed, and 1.5 kg moist grains were collected to dry and compute drying rate and the quality of dry grains in every test region. Then, dry grain was sampled 1 kg from every treatment to analyze quality of rice.Additionally, rice quality was assayed and analyzed by Supervision & Testing Center for Agricultural Product Quality, Ministry of Agriculture(Wuhan).

Table 1 Levels and codes of factors

Table 2 Experimental design and results on rice yield

Table 3 Significance test on regression models

Results and Analysis

Regression model establishment and testing

Establishment and testing of yield regression model As shown in Table 2, it is computed[5]that the regression equation of yield per hm2was as follows:

The unbiased estimation of random error was

It can be concluded that 95%confidence region of the regression model was (y±699.2) kg. According to regression model, significance test (F)can be carried out and the results(Table 3) showed that the value of F was 0.01(F0.05(1,10)=4.54)through repetitions, which indicated that treatments within a test region were of insignificant differences. Furthermore,the value of F in regression test was 21.65(F0.01(10,10)=4.85),which incorporated that it is reliable to establish a regression model reflecting the relationship of yield with yield factors. The test of partial regression coefficient demonstrated that, bx1, bx2, bx3, bx32,bx1x2, bx1x3and bx2x3reached significant differences (0.01) and bx12reached significant differences at 0.1.

Establishment of rice quality regression model and testing The test results and the prediction value indices of rice quality were shown in Table 4, covering gel consistency,amylose content, chalky rice rate, and head rice rate, and partial regression coefficients were shown in Table 5.Subsequently, the practical value and prediction value were through significance test and it is proved by F testing that differences were below significant level, which suggested that different regression equations are in consistent with practical condition.

Analysis on agronomic measure effects

Analysis on effects of individual agronomic measure The relationship of different factors with yield can be analyzed by Dimensionality Reduction and partial regression equations of density, the quantities of pure K and pure N with yield can be concluded,supposing the other factors are zero,as follows:

The monomial coefficient refers to that supposing the other two factors are zero,density (x1),the increases of K fertility (x2) and N fertilizer (x3) per unit, the yield per hm2would grow by 722.27, 182.29 and 329.17 kg, respectively. Furthermore, the orientation of a parabola can be determined by a quadratic term ratio,and the positive or negative values of the coefficients suggest minimum or maximum of a partial regression coefficient. In general,the higher the absolute value,the smaller the parabola’s openness.Hence, it can be concluded that the quadratic term ratio of the equation of three measures and yield was negative, with maximum, suggesting that the highest yield can be achieved when three measures are conducted at proper values.

Table 4 The test results and the prediction value indexes of rice quality

Table 5 The rice quality indicators of partial regression coefficient in the regression equation

Analysis on interaction effects of two factors on yield According to yield regression equation, interaction effects exist among different factors and the sign of interaction coefficient indicates the orientation of the interaction. For example, positive and negative signs suggest positive and negative interactions, and the highest absolute value, the highest interaction effect.

In the test,density(x1)was of negative interaction with both of K fertilizer(x2)and N fertilizer (x3), with significant differences at 0.01, which demonstrated that the number of basic seedlings was small in the treatment with lower density, and more N and K fertilizers would dramatically improve yield. With a high density, the number of basic seedlings was high, and a high yield can be accomplished with fewer N and K fertilizers.

In addition, K fertilizer (x2) and N fertilizer (x3) showed positive interaction effect, with significant differences at 0.01, which incorporated that when N fertilizer was applied at a high quantity,a high yield can be reached with K fertilizer at a high quantity,and when N was applied at a low quantity, a high yield could be accomplished also with K fertilizer applied at a low quantity.

Analysis on agronomic measures’effects on quality of rice It can be concluded from regression analysis of gel consistency that planting density is a dominant factor affecting gel consistency of Luyoumingzhan, and the gel consistency is improving as density grows.What’s more,the increase of N quantity would enhance gel consistency also. As for K fertilizer, gel consistency changed from increasing to decreasing with the quantity growth, but gel consistency improved to certain extent also with K fertilizer at a proper quantity(Fig.1).Meanwhile,interaction effects of density with K and N fertilizers were both negative (Table 5),which incorporated that the decreasesof N and K fertilizers would increase gel consistency of rice and improve rice tastes.

Table 6 Technical scheme and the predictive value of each index on yield ≥7 500-9 000 kg/hm2, rice gel consistency ≥70 mm, rice amylose content 15.5%-17.0%,chalky rice rate≤30%,rice head rice rate≥55%

In accordance with the regression equation of amylose, K and N fertilizers are major factors influencing the content of amylose. Specifically, the increase of K fertilizer would enhance the content of amylose.For N fertilizer,however, the increase of N fertilizer would increase the content of amylose within a certain extent.

Based on regression equation of chalky rice rate,density is a major factor affecting chalky rice rate. With proper density, the chalky rice rate would maintain low,but the rate would increase upon rice density, reducing appearance quality of rice. In addition,with K fertilizer applied at a proper quantity, chalky rice rate would drop also, but the fertilization of N fertilizer would improve chalky rice rate (Fig.3).As shown in Table 5, the interaction effect between density and K fertilizer was negative, which suggested that chalky rice rate would decline by increasing K fertilizer with a low density,or by decreasing K fertilizer with a high density.

It can be concluded from the regression equation of head rice rate is mainly under influence of density and K fertilizer.With the density increased,head rice rate would decline, and the rate would increase by application of K fertilizer (Fig.4).What’s more,the interaction effect was negative (Fig.5),which indicated that head rice rate would decline by applying K fertilizer with a low planting density, or by reducing K fertilizer with a high planting density.

Determination of a cultivation scheme of high-yielding and highlyqualified rice In order to explore a cultivation scheme of high-yielding and highly-qualified rice, statistical optimization method was used to make frequency analysis on objective function of rice yield and quality. Given that-2 ≤xi≤2 and step size at 1, 5 treatments were design of the three factors, respectively, as per full factorial design (125 factors). Subsequently,optimization test was simulated with consideration of yield,gel consistency,the content of amylose, chalky rice rate, and head rice rate[5]. Specifically,the technology combination totaled 52 with yield per hm2≥7 500-9 000 kg,taking up to 41.6% ; the technology combination totaled 63 with gel consistency≥70 mm,representing 50.4%;the technology combination reached 92, with the content of amylose in the range of 15.5%-17.0%,accounting for 73.6% ; the technology combination achieved 74 with chalky rice rate ≤30%,taking up to 59.2%; the technology combination totaled 53 with head rice rate≥55%,accounting for 42.4%.Hence, the average weighted values can be concluded (Table 6).It is obvious that with given values in different schemes differed, the prediction values of gel consistency, the content of amylose, and head rice rate were similar, with exceptions of theoretical yield and chalky rice rate, and therefore, the averages of yield and chalky rice rate can be used. Specifically, in terms of the treatment with a high yield and a low chalky rice rate, the densitywas designed-0.139 6(214 500 patches rice/hm2),K quantity at 0.077 7(K2O at 140.2 kg/hm2) and N quantity at 0.023 4 (pure N at 136.6 kg/hm2). Although the theoretical yield of the scheme with a high yield and a low chalky rice rate, was low compared with the high-yielding scheme, the original yield can be improved by corresponding cultivation and management.

Conclusions and Discussions

The research indicate that with Luyoumingzhan as test materials, the quadratic functions of yield with density,K fertilizer and N fertilizer were parabolas, and the regression equation fitted well with practical ones.What’s more, a high yield of the cultivar can be accomplished with optimal density,K and N fertilizers,and the effects of the three factors on yield coincide with researches available[7-9].

As a comprehensive character,rice quality, including appearance quality and tastes, are mainly controlled by genetic factor,as well as environment and nutrients, although the specific index shows different sensitivity degrees.

The content of amylose is the most important one of physicochemical indexes influencing rice tastes,whose content has a deciding effect on rice stickiness and softness[10]. In China,the rice with content of amylose in to the range of 8%-17% is called soft rice which tastes soft and sweet,with elasticity[11]. According to the test,within a certain range, the effects of the three factors on amylose content of Luyoumingzhan are in the range of soft rice, which suggested that the cultivar is of stable excellent texture, and the factors, including unpolished rice rate, milled rice rate, rice length,length-to-width rate, chalky degree,transparency rate, alkali spreading value,and protein content,are less affected by the three cultivation measures, with insignificant differences. In addition,among gel consistency,head rice rate, and chalky rice rate, only chalky rice rate showed considerable differences in the high-yielding scheme,which can be improved by interaction coordination.Hence,it is necessary to make adjustments on the cultivation measures in order to achieve the integration of both high yield and high quality. The test has proved that a rational combination of cultivation factors makes it possible for Luyoumingzhan to get a high yield with highly-qualified property.

Further analysis demonstrated that among the three cultivation measures, density is a dominant factor affecting chalky rice rate, and the highest chalky rice rate, the lower head rice rate, but with density increased,gel consistency would grow also. As for the effects of density on rice quality,more researches have been carried out on the aspect. For instance, Jin[12],Zhou et al.[13], and Hu et al.[14]researched that the increase of density would enhance chalky rice rate and reduce head rice rate. Xu et al.[15]believed that the increase of density would decrease head rice rate. Hu et al.[14]explored that gel consistency changed from increasing to decreasing under influence of density. Ding[16]investigated that the growth of density would improve gel consistency.Therefore, the research is in consistent with researches available. Nevertheless,the research[17]indicated that density has insignificant effects on gel consistency, the content of amylose and chalky rice rate. The research of Zhong et al.[18]showed that density is of insignificant correlation with rice quality.Xu et al.[15]believed that the increase of density would even decrease gel consistency. Still, the differences are possibly caused by test variety and fertilizers.

In terms of the effects from fertilizer quantity, the test showed that the increase of N fertilizer would improve chalky rice rate and gel consistency,which coincides with researches available. For example, Hu et al.[14]investigated that the increase of N fertilizer would improve gel consistency and chalky rice rate changed from increasing to decreasing. Zhang et al.[19]concluded that the increase of N fertilizer would enhance gel consistency and chalky rice rate. Xu et al. believed that under influence of N fertilizer,chalky rice rate changed from increasing to decreasing. Ding[16]and Zhou[20]concluded that the increase of N fertilizer would increase chalky rice rate.However, the research made by Xu et al.[15]and Ding[16]suggested that the increase of N fertilizer would reduce gel consistency. Hence, the effects of N fertilizer on gel consistency possibly vary considerably upon rice variety.Previous researches demonstrate that K fertilizer has effects on rice quality,and the effects tend to be volatile upon variety.Hu et al.[21]explored that with K fertilizer increased, chalky rice rate of Lianjiajing 1 changed from increasing to decreasing, but of Wuyujing 3 was decreasing. The research of Wang et al.[22]indicated that the increase of K fertilizer would improve head rice rate,chalky rice rate and chalky degree.Wang et al.[23]made research which demonstrated that K fertilizer quantity was of extremely significant positive correlation with the content of amylose.The research proved that K fertilizer at a proper quantity would improve gel consistency and reduce chalky rice rate.

On basis of simulation, the optimized technology combination involves density at -0.139 6 (214 500 patches rice/hm2),K quantity at 0.077 7 (K2O at 140.2 kg/hm2),and N quantity at 0.023 4 (pure N at 136.6 kg/hm2),and interactions among the factors should be well considered to improve rice quality and quantity simultaneously.

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