| Plant type characteristics of high yielding cultivars of double cropping rice19 early rice cultivars and 16 late rice cultivars were used to study the plant type characteristics of stems, leaves and spikes in the experimental fields of science and technique demonstrating garden of Jiangxi Agricultural University and Wenzhen town Jinxian county Jiangxi province from 2005-2007. The main results were as follows. For double cropping rice, high yielding cultivars had the characteristics of large number of spikelets, high panicle weight and plant height and the powerful abilities of dry matter production and N uptake. But some differences in plant type were also existed between early rice and late rice. For early rice, about 110 d of growth duration, high plant height (95-105cm), long length and big angle of the second and third leaves to top, long length of the panicle, large numbers of second branches of panicle, 100-130 spikelets per panicle, and big weight of grain (27-29g for 1000-grains). For late rice, about 120-125 d of growth duration, high plant height (100-110cm), long length of the top internode, middle length and lesser angle of the top three leaves, wide stem, long spike, large numbers of second branches of spike, high density of the grains, large number of the grains (120-150 grains per panicle), 25-27 g for 1000-grains weight. Part 2 Plant type indices of high yielding population of double cropping rice in main growth stageIn the experimental fields of science and technique demonstrating garden of Jiangxi Agricultural University and Wenzhen town Jinxian county Jiangxi province from 2004-2007, three early rice cultivars Jinyou463, Luliangyou996, Ganxin203 and five late rice cultivars Ganxin688, Xiannong16, Zhongyou329, Shanyou963 and Yueyou9113 were used to study the plant type indices for the population with the yield over 9000kg/hm2 in the stages of ( N-n ) leaf age, panicle initiationⅡ, full heading and milky on the experiments of nitrogen application amount, top addressing stage for nitrogen, nitrogen application amount and planting density, basal and top dressing ratio of nitrogen, planting density, seedling age, application amount of bean cake fertilizer by using the methods of variance analysis, path analysis, correlation analysis and regression analysis. The main results were as follows.1. Plant type indices of high yielding population of double cropping rice in (N-n) leaf age stageFor early rice, seedlings number per hectare was 3.45-4.00 million, N contents in leaves was 5.23%-5.5%, RSPAD was 0-6%, LAI 0.8-1.0 and dry matter accumulation was 550-610 kg/hm2.For late rice, seedlings number per hectare was 3.75-4.15 million, N contents in leaves was 4.17%-4.55%, RSPAD was 5%-8%, LAI 3.2-3.7 and dry matter accumulation was2200-2500 kg/hm2.2. Plant type indices of high yielding population of double cropping rice in panicle initiationⅡstageFor early rice, seedlings number per hectare was 5.70-6.15 million and the number of the seedling over 0.15 g was 3.80-4.05 million, tiller-panicle ratio 49%-62%, N contents in leaves was 3.83%-4.37%, LAI4.1-4.8 and dry matter accumulation was 3000-3500kg/hm2. For late rice, seedlings number per hectare was 5.05-5.80 million and the number of the seedling over 0.30 g was 3.50-4.00 million, tiller-panicle ratio 57%-77%,N contents in leaves was 2.66%-3.06%, LAI6.4-7.0 and dry matter accumulation was 5500-6400kg/hm2.3. Plant type indices of high yielding population of double cropping rice in full heading stageFor early rice, 93-107cm height of the plant, 30-35cm length for top internode,17-20cm length for the second internode, 15-18cm length for the third internode, 20-28cm length for the flag leaf, 37-47cm length for the second leaf, 43-51cm length for the third leaf, 8°-12°for the angle of the flag leaf, 18°-21°for the angle of the second leaf, 25°-42°for the angle of the third leaf, 38.60-43.10 million per hectare for the total number of spikelets, 3.55-3.95 million per hectare for the effective number of panicle, over 96% for the tiller of 1/0 for panicle, over 92% for the tiller of 2/0 for panicle, over 54% for the tiller of 3/0 for panicle, over 14% for the tiller of 4/0 for panicle, 6.2-7.6 for LAI, 3.0%-3.4% for N contents in leaves, 20-26 for population index, 8220-9420kg/hm2 for dry matter accumulation.For late rice, 105-110cm height of the plant, 28-30cm length for top internode,17-19cm length for the second internode, 12-17cm length for the third internode, 23-34cm length for the flag leaf, 39-51cm length for the second leaf, 49-58cm length for the third leaf, 8°-13°for the angle of the flag leaf, 10°-16°for the angle of the second leaf, 16°-19°for the angle of the third leaf, 44.30-50.20 million per hectare for the total number of spikelets, 3.00-3.85 million per hectare for the effective number of panicle, over 93% for the tiller of 2/0 for panicle, over 82% for the tiller of 3/0 for panicle, over 58% for the tiller of 4/0 for panicle, over 18% for the tiller of 5/0 for panicle, over 38% for the tiller of 1/1 for panicle, over 30% for the tiller of 2/1 for panicle, over 11% for the tiller of 3/1 for panicle, 7.4-8.0 for LAI, 2.6%-3.2% for N contents in leaves, 19-26 for population index, 10500-10950kg/hm2 for dry matter accumulation.4. Plant type indices of high yielding population of double cropping rice in milky stageFor early rice, LAI was 5.5-6.5, decrease range of chlorophyll contents was 5-10%, light transmittance 5cm above ground was 3%-6%, light transmittance 30cm above ground was 5%-7%, under the condition of optimal spikelets number, weight adding per grain after full heading was 1.11-1.35mg in 5 days, 1.71-1.95mg in 5-10 days, 0.55-1.47 mg in 10-15 days, 0.14-0.62 in 15-20 days, 0.03-0.53 mg in 20-25 days, dry matter accumulation was 12600-13400kg/hm2 in milky stage and 5350-6220kg/hm2 after full heading and 14400-15100kg/hm2 in the total.For late rice, LAI was 6.5-7.5, decrease range of chlorophyll contents was 5%-10%, light transmittance 5cm above ground was 1%-2%, light transmittance 30cm above ground was 2%-3%, under the condition of optimal spikelets number, weight adding per grain after full heading was 1.03-1.23mg in 5 days, 1.14-1.42mg in 5-10 days, 0.59-1.31 mg in 10-15 days, 0.13-0.81 in 15-20 days, 0.01-0.45 mg in 20-25 days, 0.04-0.30 mg in 25-30 days, dry matter accumulation was 13500-15000 kg/hm2 in milky stage and 5140-5650kg/hm2 after full heading and 15770-16470kg/hm2for the total.Part 3 Regulating of the plant type indices of high yielding population for double cropping riceDuring studied on the plant type indices, the effects of cultivation measures on tiller for panicle, plant characteristic, matter production and transportation were also discussed. The main results were as follows.1. Main limiting factors for yield formation of double cropping riceMain limiting factors for the yields of early rice were panicle number and grain number per panicle, and for the yields of late rice were panicle number and Filled grain ratio. So, the most effective way to enhancing yields for early rice was adding panicle number and grain number per panicle, and for late rice was enhancing grain filled ratio on the base of obtaining optimal panicle number.2.Effects of nitrogen application amount on plant type indices of double cropping riceOptimal nitrogen application amount increasing the contents of nitrogen in leaves, promoting tillering growth, increasing the number and the rates of the tillering over the critical stem-weight for panicle, adding panicle number and enhancing the dry matter accumulation before full heading. Optimal nitrogen application amount also increaseing plant height, adding the length of top three internodes and leaves, enhancing LAI and the contents of chlorophyll in leaves.Excessive application of nitrogen can't enhance the nitrogen contents in leaves significantly, but decrease the ratio of tillering over the critical weight for panicle due to a lot of ineffective tillering, reduce the number of grains per panicle and the filled grain ratio, decrease dry matter accumulation from milky to maturity and the total duration because of the sharp declining of LAI.The optimal nitrogen application amount was 80-225kg/hm2, and less for small panicle rice cultivar and more for big panicle rice cultivar.3. Effects of top application stage of nitrogen on plant type indices of double cropping riceFor nitrogen, top application earlier was benefit for tillering adding and the tiller-panicel ratio increasing. Top application at early stage can increase the dry matter production before full heading and enhance the matter transport rate in stem, but reduce the dry matter accumulation amount of anaphase. Top application at middle stage can burst a lot of ineffective tillering and decreased the tiller-panicel ratio, at the same time, it can add the length and the angle of the top leaves, and made leaves dropped. Top application at late stage can increase the panicle number and the grain number per panicle, and enhance the content of chlorophyll in leaves, add the dry matter accumulation amount of anaphase, but too earlier for top application can prolong leaf length, increase LAI, and add leaf angle, drop grain-leaf ratio.Appropriate time for top application of nitrogen was 5 days after transplanting and the stage of the second leaf to top shooting out.4. Effects of transplanting density on plant type indices of double cropping rice Low transplanting density was benefit for tiller of high node and second order to grow into panicle, and put off the leaf age for getting enough seedling, thus added the plant plasticity of rice population. When nitrogen application amount was low, high transplanting density increased the number of panicle and LAI. When nitrogen application amount was high, low transplanting density can also get a high LAI, and the LAI dropped more slowly than high transplanting density population, which was benefit for the adding of grain number per panicle and grain-leaf ratio, and promoting dry matter production and the matter transport rate.The optimal planting density for double cropping rice was 250000-320000 holes per hectare. Under the conditions of low nitrogen application and weak tillering ability, high density is good, and under the conditions of high nitrogen application and strong tillering ability, middle density is better.5. Effects of nitrogen application ratio of base and topdressing on plant type indices of double cropping riceHigh ratio of basal nitrogen application increased the nitrogen contents in leaves, promoted tiller growth, added panicle number, enhanced dry matter accumulation before full heading and the matter transport rate, but was not so good for dry matter production of anaphase. Optimal ratio of nitrogen application was benefit to harmonizing panicle number and grain number and obtaining large number of total grains and enhancing the yields. The optimal ratios of nitrogen application were 7:3 for early rice, and 6:4 for late rice cultivar of heavy panicle, 7:3 for late rice cultivar of middle panicle.6. Effects of seedling age on plant type indices of double cropping rice With the short seedling age, rice had a high speed of tillering in early stage and had an advanced fastigium of tillering, which promoted the tiller of low node to grow into panicle and enhanced the number of panicle and total grains, and made a high yield. The optimal seedling age for double cropping rice was 20-25 d. |
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