Effects of Different Application Times of Tillering Fertilizer on Grain Yield and Population Development of Double-cropping Rice Transplanted by Machine

Qingyin SHANG, Weisheng LU, Yongjun ZENG, Shan HUANG, Xiuxia YANG, Xueming TAN,Qinghua SHI, Xiaohua PAN

Collaborative Innovation Center for the Modernization Production of Double Cropping Rice/Key Laboratory of Crop Physiology, Ecology and Genetic Breeding, Ministry of Education/Jiangxi Key Laboratory of Crop Physiology, Ecology and Genetic Breeding,Jiangxi Agricultural University, Nanchang 330045, China

With the social and economic development, agricultural restructuring and rural labor transfer, the existing traditional cropping pattern of rice has been unable to meet the requirements by social development. The mechanical trans planting, along with supporting cultivation techniques, is an advanced technology in line with the development direction of modern cultivation of rice. So, it has a very broad appli-cation prospect[1]. However, there are still many problems in mechanical transplanting of rice in China, such as slow tillering, less dry matter accumulation and delayed appearance of highest tiller number of early rice in doublecropping areas in Southern China.Although mechanically-transplanted late rice tiller earlier with higher tiller number,there are less dry matter accumulation and lower earbearing tiller percentage in the early tillering stage[2].So, how to promote the tillering of mechanically-transplanted rice seedlings in the early stage is the key to obtain high yield.

Numerous studies have shown that the application of tillering fertilizer has an important impact on rice tillering, yield and quality[3-8]. At present,there are some reports on application time of tillering fertilizer in China. In Northern China, tillering fertilizer is generally considered to be applied within 10 d after rice seedling turn green[7,9-10].In the double cropping areas of rice, such as Jiangxi and Human, the traditional experience advocates applying tillering fertilizer within 5-7 d after the transplanting to promote growth of rice seedlings. However,there are also some researchers suggesting that tillering fertilizer should be applied on day 13 since the transplanting of early rice and on day 11-14 d since the transplanting of late rice to control pests and diseases[11-12].The studies above provide an important guide for application of tillering fertilizer.However,they all focus on conventionally-transplanted rice. Mechanical transplanting has higher nursing density, shorter seedling age, but imperfect quantitative cultivation techniques.It shows obvious differences in cultivation and management techniques compared with conventional manual transplanting[5]. Therefore, the optimal application time of tillering fertilizer for mechanically-transplanted rice still needs to be further clarified.

Jiangxi Province is one of the typical double-cropping areas of rice in China. The acreage of rice in Jiangxi Province ranks second, and the proportion of paddy fields in arable land in Jiangxi Province ranks first across China[13]. The study on optimal application time of tillering fertilizer has great significance in further promotion of mechanical transplanting technology in Jiangxi Province. Therefore, in this study, the double cropping rice was used as the research object, and the effects of different application times of tillering fertilizer on growth and development and yield of mechanicallytransplanted rice were primarily discussed, proving a scientific basis for the promotion of mechanical transplanting technology in double cropping rice.

Materials and Methods

Materials

The test was conducted in the demonstration zone of Biaoxing Agricultural Technology and Machinery Cooperatives in Jingkou Town, Nanchang County, Jiangxi Province in 2013.Before the test,the basic physical and chemical properties of the soil were as follows:organic matter of 33.6 g/kg,total nitrogen of 1.38 g/kg,alkalihydrolyzable nitrogen of 95.5 mg/kg,available phosphorus of 18.8 mg/kg,available potassium of 93.6 mg/kg and pH of 5.12. The early rice cultivar was Zhongjiazao 17,and the late rice cultivar was H You 518. Zhongjiazao 17 is also named as Jiayu 253 or 04YK17.It is a new super high-yielding rice cultivar bred by the China National Rice Research Institute and Zhejiang Academy of Agricultural Sciences.Zhongjiazao 17, characterized by high yield,wide adaptability,short plant and large ears, is a thermal-sensitive and middle-mature early indica rice with whole growth period of about 110 d. H You 518 is a late rice cultivar bred by Hunan Agricultural University and Hengyang Institute of Agricultural Sciences. Its whole growth period is 108 d. H You 518 has characteristics of loose plant type, long and erect flag leaf and colorless sheath and apiculus.

Test design

The standard trays in length of 58 cm, width of 28 cm and height of 2.8 cm for mechanical transplanting were adopted. Before the sowing, a certain amount (4 kg) of subsoil was laid on each of the trays.The subsoil was collected from the topsoil of paddy fields.In addition, certain amounts of seedling strengthen agent(0.3%of the mass of subsoil) and compound fertilizer(0.5%of the mass of subsoil)were added to each of the trays.The tillering fertilizer was applied 7(D07),10(D10)and 13 (D13) d after the transplanting,respectively.

Both early and late rice seedlings were nursed in plastic soft trays (58 cm×28 cm×2.8 cm).The early rice was sowed on March 19th with seeding rate of 100 g/tray. The early rice seedlings were transplanted on April 19th.The late rice was sowed on June 25th with seeding rate of 90 g/tray.The late rice seedlings were transplanted on July 18th. The row and plant spacing of both early and late rice was all 30.0 cm×13.3 cm.The rice seedlings were all transplanted by high-speed transplanter. The other management measures were the same with those of conventional high yield cultivation.

The area of each plot was all 220 m2. There were three replications for each treatment. Among the treatment groups,the application amount of fertilizer was the same. The basal fertilizer was 450 kg/hm2of compound fertilizer (15% N, 15% P2O5and 15%K2O), the tillering fertilizer was 150 kg/hm2of urea (46% N) and 112.5 kg/hm2of potassium chloride (60%K2O), and the panicle fertilizer was 75 kg/hm2of urea. For the early rice, the basal fertilizer, tillering fertilizer and panicle fertilizer were applied on April 18th, April 26thand May 23th, respectively;while for the late rice, they were applied on July 17th, July 24thand August 20th, respectively. During the test,the drainage was carried out in the middle period after 80%-90% of the planned spikes emerged. The pests and diseases control and weeding were carried out regularly to maintain a normal growth and development of rice plants.

Indicator measurement and methods

Tillering dynamics and leaf area index Total 20 rice plants were sampled in each plot.They were vertical to transplanting direction with 10 on each side. The tiller numbers and leaf area indexes were investigated at tillering,booting, heading and mature stages,respectively.

Dry matter accumulation and nitrogen uptake According to the aver-age sampling method, total five plants were sampled from each of the plots at the tillering, booting, heading and mature stages, respectively. The rice plants were divided into three parts,leaf, stem-sheath and panicle (after heading).The rice plant samples were dried at 105 ℃for 15 min and then at 80 ℃to constant weight. Subsequently,they were weighed.After the determination of dry matter accumulation,the rice samples collected at the mature stage were boiled in H2SO4-H2O2,and then the nitrogen uptakes were determined using a flow analyzer.

Yield determination and seed test

The effective tiller numbers were investigated 2 d before the harvesting.In each plot, total 30 rice plants were sampled. Based on the average tiller numbers, total five rice plants were sampled from each plot for seed test.In each plot, total 200 rice plants were harvested for determination of yield.

Data processing and statistics

The data were processed and analyzed using Excel 2003 and JMP10.0(SAS Institute,Cary,NC,USA,2011).

Results and Analysis

Effects of different application time of tillering fertilizer on yield and yield components of rice

Among the treatment groups, the application time of tillering fertilizer showed no significant effect on yield of early or late rice (P＞0.05). However,when the tillering fertilizer was applied on day 7 since the transplanting, the rice yield was higher. Compared with those in the D07 treatment group, the yields of early rice in the D10 and D13 treatment groups were reduced by 9.4% and 3.8%, respectively, and the yields of late rice in the D10 and D13 treatment groups were reduced by 4.5% and 12.6%, respectively. In the early rice season, there were no significant differences in effective tiller number and 1 000-grain weight among the treatment groups. Compared with those in the D07 treatment group, the grain numbers per panicle in the D10 and D13 treatment groups were reduced by 20.6% and 3.6%, respectively, and the seed setting rates were reduced by 1.2% and 13.8%, respectively.The grain number per panicle in the D10 treatment group was significantly lower than that in the D07 treatment group, and the seed setting rate in the D13 treatment group was significantly lower than that in the D07 treatment group (P＜0.05). In the late rice season,no significant differences were observed in grain number per panicle,seed setting rate or 1 000-grain weight among the treatment groups. Compared with that in the D07 treatment group, the effective tiller numbers in the D10 and D13 treatment groups were decreased by 6.7%(P＞0.05)and 13.9%(P＜0.05),respectively.

Between the seasons, the rice yield was higher in the late season,accounting for 56.5%-60.1% of the annual production of double-cropping rice (Table 1). The variance analysis showed that the rice yield in the late season was higher than that in the early season(paired t-test).In terms of yield components,there were small differences in grain number per panicle,seed setting rate and 1 000-grain weight between early and late rice.However, the average effective tiller number of late rice was 32.2%-38.9%higher than that of early rice.

Table1 Effects of tillering fertilizer applied at different times on yield and yield components of rice

Effect of different application time of tillering fertilizer on tillering of rice

As shown in Fig.1, the variation trends of effective tiller number of both early and late rice were basically the same.From tillering to booting stages,the effective tiller numbers were all trended to be increased; from booting to heading stages, the effective tiller numbers started to decline;from heading to mature stages,the effective tiller numbers were decreased insignificantly. The variance analysis showed that the tiller number in the late rice season was higher than that in the early rice season (paired t-test). At the booting stage,the tiller numbers of late rice were higher than those of early rice by 35.0%-41.5%. At the mature stage, the tiller numbers of late rice were higher than those of early rice by 32.2%-49.6%.

Among the treatment groups, the effective tiller numbers of early and late rice were all highest in the D07 treatment group (excepting those of early rice at tillering and mature stages,Fig.1).In the early rice season,the effective tiller number differed significantly at the booting stage, but it showed no significant differences a-mong the treatment groups at the mature stage (Table 1). At the booting stage, the effective tiller numbers in the D10 and D13 treatment groups were reduced by 5.8%and 12.6%,respectively compared with that in the D07 treatment group. In the late rice season, the tiller number differed significantly among the treatment groups excepting at the tillering stage. At the booting stage,the tiller numbers in the D10 and D13 treatment groups were 1.3% and 9.0% lower than that in the D07 treatment group;while at the mature stage,they were 6.7%and 13.9%lower than that in the D07 treatment group. At the mature stage, the tiller number in the D13 treatment group was significantly lower than that in the D07 treatment group(Table 1).

Effect of different application time of tillering fertilizer on leaf area index of rice

From the tillering to booting stages, the leaf area indexes (LAIs) of various treatment groups were all trended to be increased.The leaf area indexes of early rice were increased by 250.7%-369.4% from the tillering to booting stages, while the leaf area indexes of late rice were increased by 146.4%-159.3% (Fig.2). In the late rice season, the leaf area indexes of various treatment groups were increased continuously. However, the increments of leaf area index of early rice were smaller. Compared with those at the booting stage, the leaf area indexes of late rice at the heading stage were increased by 31.6% -52.8%, while of early rice were increased by only 8.9%-39.2%.

Among the treatment groups, the leaf area index of rice was trended to be decreased with the delayed application of tillering fertilizer. However,the leaf area index differed significantly among different growth stages (Fig.2).Among the growth stages, the differences in leaf area index were smaller at the tillering stage. Compared with those in the D07 treatment group, the leaf area indexes of early rice in the D10 and D13 treatment groups were reduced by 14.8% and 30.2% , respectively at the booting stage, while of late rice were reduced by 12.5%and 12.7%. At the heading stage, the leaf area indexes of early rice in the D10 and D13 treatment groups were reduced by 17.9%and 14.1%,respectively compared with that in the D07 treatment group,while of late rice were reduced by 15.8%and 24.9%.

Effect of different application time of tillering fertilizer on dry matter accumulation in rice

In the early rice season, the variation of dry matter accumulation in the whole growth period was basically the same among different treatment groups, but the dry matter accumulation was higher in the D07 treatment group (Fig.3). Compared with that in the D07 treatment group,the dry matter accumulations in the D10 and D13 treatment groups were reduced by 21.6% and 6.2%, respectively at the mature stage.However,the proportion of dry matter accumulated after the flowering (during the heading to mature stages) was trended to be decreased with the advanced application of tillering fertilizer. The proportions of dry matter accumulated after the flowering in the D07, D10 and D13 treatment groups were 44.1%, 43.5% and 51.9%,respectively.

In the late rice season, the variation of dry matter accumulation from the tillering to booting stages was basically the same among various treatment groups. The differences in dry matter accumulation were relatively small among different treatment groups.After the booting stage,the increase trend of dry matter accumulation was similar between the D10 and D13 treatment groups, but the dry matter accumulations in the D10 and D13 treatment groups were 26.3%-28.5% lower than that in the D07 treatment group. At the mature stage,the dry matter accumulations in the D10 and D13 treatment groups were 11.5% and 22.1% lower than that in the D07 treatment group. Similar to early rice, the proportion of dry matter accumulated in late rice after the flowering was also trended to be decreased with the advanced application of tillering fertilizer. In the D07, D10 and D13 treatment groups, the proportions of dry matter accumulated after the flowering were 24.8%, 39.2%and 28.9%,respectively.

Effect of different application time of tillering fertilizer on nitrogen uptake of rice

As shown in Fig.4, there were nosignificant differences in nitrogen uptake among the treatment groups in the early or late rice season.However,the nitrogen uptakes in both early rice and late rice were all trended to be decreased with the delayed application of tillering fertilizer. Compared with those in the D07 treatment group, the nitrogen uptake by early rice in the D10 and D13 treatment groups were reduced by 15.4% and 16.0% , respectively, while by late rice were reduced by 11.7% and 21.6%, respectively.

Discussion

Rational application of tillering fertilizer is an important measure in highyielding cultivation of rice transplanted by machine. It plays an important role in obtaining optimal population and appropriate spikes. Moreover, tillering fertilizer has great impacts on yield and quality of rice[5-7].At present,there are rare researches on application time of tillering fertilizer in double cropping rice in China. This study showed that under condition of mechanical transplanting, tillering fertilizer had no significant effect on yield of double cropping rice. However, appropriately early application of tillering fertilizer was conducive to obtaining high yield,and this is similar to the findings on traditionally-transplanted rice[6-7,9].

In terms of yield components,different application time of tillering fertilizer had greater effect on effective tiller number of late rice. Compared with that in the D07 treatment group,the effective tiller numbers per unit area of late rice in the D10 and D13 treatment groups were increased by 8.4% and 16.1%, respectively. In addition, the seed setting rates of both early and late rice were trended to be decreased with the delayed application of tillering fertilizer.Han et al.[7]found that in uplands of Northern China, with the delayed application of tillering fertilizer,the effective tiller number per unit area of rice was increased, but the grain number per panicle, seed setting rate,1 000-grain weight and yield were decreased gradually. In addition, the incidence of panicle blast in rice was increased gradually, but the milled rice rate and head rice rate were reduced gradually with the delayed application of tillering fertilizer[9-10].

From the perspective of population development, the appropriately advanced application of tillering fertilizer could increase tiller number per unit area, leaf area index, biomass accumulation and nitrogen uptake. Liu et al.[14]found that tillering fertilizer should be applied appropriately in advance,and it could increase nutrient absorption and leaf area index of plants through promoting root vigor and tillering ways.Conversely,with the delayed application of tillering fertilizer,the heading and maturity of rice were delayed, thus the height of rice plants was increased, and reluctant ripen was prone to occurring, greatly increasing the chance of lodging[6,9].

However,there are also some researches believing that under conditions of adequate basal fertilizer and appropriate planting density,appropriately delayed application of tillering fertilizer can also improve effective tiller number of rice[11].In this study,no significant differences were observed in effective tiller numbers per unit area of both early and late rice between the H07 and D10 treatment groups, but the effective tiller number of late in the D13 treatment group was significantly lower than that in the D07 treatment group (Table 1), indicating that under condition of mechanical transplanting,delayed application of tillering fertilizer is not conducive to tillering and dry matter accumulation of rice.

It is worth noting that climate differs significantly during the cultivation of double cropping rice in Jiangxi Province. The whole-year test is difficult to reflect the impact of climate variability on application effect of tillering fertilizer in mechanically-transplanted rice.In addition,rational application of tillering fertilizer should also take cultivar characteristics, cultivation pattern and tillering requirements by seedlings into account. Therefore, under condition of mechanical transplanting, optimal application time of tillering fertilizer still needs in-depth studies.

Conclusions

The yields of early and late rice were all highest when tillering fertilizer was applied 7 d after the transplanting.Different application time of tillering fertilizer showed significant effects on grain number per panicle and seed setting rate of early rice. The grain number per panicle in the D10 treatment group was significantly lower than that in the D07 treatment group,and the seed setting rate in the D13 treatment group was significantly lower than that in the D07 treatment group(P＜0.05). Different application time of tillering fertilizer showed significant effect on effective tiller number of late rice, and the effective tiller number in the D07 treatment group was significantly higher than that in the D13 treatment group. Appropriately advanced application of tillering fertilizer is conducive to effective tiller number per unit area,leaf area index,biomass accumulation and nitrogen uptake.Therefore,under condition of mechanical transplanting, tillering fertilizer should be best applied on day 7-10 since the transplanting of rice seedlings.

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