摘要：
Elastic sowing dates (ESDs) are correlated with rice grain yield. ESD is the easiest factor for farmers to manipulate in mechanized large-scale farming. In this study, field experiments were conducted over a 2-year period to determine the effects of different sowing dates on growth duration, effective accumulated temperature, and yield attributes in two early- and late-season machine-transplanted rice cultivars. In early rice (ER), a delay in the sowing date led to decreased grain yield and shorter growth duration. In late rice (LR), delayed sowing led to significantly lower grain yield and prolonged growth duration. In LR, significantly positive correlations were detected between effective accumulated temperature in the post-heading stage and both filling ratio and yield. Reproductive redundancy increased markedly in LR, by 7.72% over a 5-day interval. We determined that the ESDs for LR were 10 days later than the control, and that of ER was recommend early sowing rather than late sowing. These findings suggest a new strategy to meet the demands of mechanized large-scale rice farming: the development of thermal sensitive high-yield long-duration ER cultivars and high-yield short-duration LR cultivars.
作者机构：
[唐启源] College of Agronomy, Hunan Agricultural University, Changsha, 410128, China;[朱天彪; 邵迪; 舒星] College of Life Science and Technology, Honghe University, Mengzi, 661199, China;[杨永兵; 王岳东] Agricultural Maechinery Research Institute of Yunnan Honghe Hani and Yi Autonomous Prefecture, Mengzi, 661100, China;[雷恩] College of Agronomy, Hunan Agricultural University, Changsha, 410128, China, College of Life Science and Technology, Honghe University, Mengzi, 661199, China
通讯机构：
[Tang, Q.-Y.] C;College of Agronomy, China
关键词：
玉米;机械粒收;器官含水率;力学强度;籽粒破碎率
摘要：
在玉米正常收获期间,明确器官含水率、力学强度和机收质量的变化规律,探明影响籽粒机收效果的直接因素,对实现玉米籽粒机收和提升机收质量具有重要意义.本试验以两个不同熟性品种为材料,采用半喂入式籽粒收割机,开展分期收获的田间试验研究.结果 表明,籽粒静态压碎强度(耐破碎性)和籽粒与穗轴连接强度(易脱粒性)分别与籽粒破碎率形成了直接的因果关系,两者同是影响破碎率的关键因素.籽粒压碎强度(x)与破碎率(y)可高度拟合为二项式回归关系(R 2=0.8827,P<0.001),回归方程为(y)=0.0021x 2-1.5443x+293.78,籽粒和穗轴连接强度(x)与破碎率(y)可高度拟合为幂函数型回归关系(R 2=0.7656,P<0.001),回归方程为(y)=0.007 x 4.12,而穗轴弯折强度与破碎率之间的关系小于上述(R 2=0.1644,0.01<P<0.05).在玉米收获后期,虽然早熟品种'金玉99'的籽粒与穗轴连接强度明显小于晚熟品种'宝玉9号',但是'宝玉9号'的籽粒压碎强度却显著大于'金玉99',最终导致两品种的籽粒破碎率差异不显著(P>0.05).落地籽粒损失率除了与植株倒伏倒折有关以外,对刀式割台容易在果穗脱粒前产生落地籽粒损失,并且越容易脱粒的籽粒损失越大,籽粒含杂率总体上随杂质器官含水率的下降而显著降低.适宜籽粒机收的玉米品种应具备的主要特征是茎秆坚韧抗倒伏、籽粒坚硬易脱粒.
摘要：
<jats:p>Growth and development of spikelets are asynchronous during hybrid rice seed production. However, knowledge is limited about the variation in seed vigour between superior and inferior spikelets. The main objective of this study was to evaluate the differences in seed vigour between
superior and inferior spikelets of hybrid rice, and to explore the mechanisms associated with such variations with regards to seed filling characteristics and starch accumulation. Field experiments were conducted in 2017 and 2018, and seed vigour parameters, seed filling characteristics and
starch accumulation were determined. We found that significant differences were recorded in seed vigour parameters between superior and inferior spikelets. Germination percentage (GP) and vigour index (VI) of superior spikelets were higher than that of inferior spikelets, irrespective of year
or variety. Moreover, significant differences were observed in seed filling characteristics and starch accumulation between superior and inferior spikelets. Lower total starch content, amylose content and amylopectin content were recorded in inferior spikelets with low seed filling rate and
long seed filling duration. Superior spikelets with high seed filling rate and short seed filling duration increased final seed weight by 23.9 and 22.3% for each variety, respectively. Therefore, these results raise the possibility that seed filling influences the starch accumulation and seed
weight, and is closely associated with differences in the vigour of seeds from superior and inferior spikelets during hybrid rice seed production.</jats:p>
摘要：
<jats:title>Abstract</jats:title><jats:p>High‐density planting is a strategy employed to save resources in crop production, particularly in environmentally friendly double‐season rice (<jats:italic>Orvza sativa</jats:italic> L.) cropping, where it promotes high grain yield and reduces required nitrogen (N) input. We conducted a field experiment in 2014–2018 to detect the combined effect of increased seedling density and reduced N input on early rice grain yield and N use efficiency (NUE). The higher basic seedling with low N input treatment (T2) had an average grain yield of 7.01 t ha<jats:sup>−1</jats:sup>, which was 16.3% greater than that of the control (CK). There was a strong linear relationship between grain yield and panicles m<jats:sup>−2</jats:sup> (<jats:italic>R</jats:italic><jats:sup>2</jats:sup>=.82, <jats:italic>P</jats:italic><.001). Grain yield increased significantly with above‐ground biomass before the full‐heading stage (<jats:italic>R</jats:italic><jats:sup>2</jats:sup>=.79, <jats:italic>P</jats:italic><.001), which in turn promoted an increase in panicles m<jats:sup>−2</jats:sup> (<jats:italic>R</jats:italic><jats:sup>2</jats:sup>=.85, <jats:italic>P</jats:italic><.001). Mean agronomic efficiency (AE) in the T2 treatment was 34.3kg kg<jats:sup>−1</jats:sup> N, which was 48.1% higher than that in the CK treatment. Therefore, increasing seedling density from 62.5 to 176 seedlings number m<jats:sup>−2</jats:sup> while reducing inorganic N input in the early season resulted in significantly higher grain yield in hand‐transplanted rice production. Our results indicate that dense planting with N reduction could improve early rice grain yield and enhance NUE.</jats:p>
摘要：
Seed filling is crucial for seed vigor and starch accumulation and structure. Differences in hybrid rice seed vigor were evaluated in field experiments, conducted across two sites in 2017 and 2018, under different seed filling temperatures along with the underlying mechanisms related to the seed filling characteristics and starch accumulation and structure. Significant differences in the seed vigor parameters were revealed, with different seed filling characteristics observed under different temperatures. When averaged across cultivars, the seeds with a low seed filling rate and long seed filling duration obsessed 11.9% higher germination percentage (GP) and 22.7% higher vigor index (VI) than those with a high seed filling rate and short seed filling duration. Moreover, a high seed filling rate and short seed filling duration significantly decreased the total starch and amylose contents and increased the amylopectin content. Additionally, when averaged across cultivars, the relative crystallinity and starch granule diameter obtained with a high seed filling rate and short seed filling duration were 3.8% and 15.1% higher, respectively, than those with a low seed filling rate and long seed filling duration. In summary, it can be speculated that seed filling characteristics determine hybrid rice seed vigor by affecting starch accumulation and structure.
关键词：
annual yield;double rice;nitrogen use efficiency;ratoon rice
摘要：
<jats:title>Abstract</jats:title>
<jats:p>Simple and practical water-saving irrigation practices (WIP) with nitrogen-reduction are beneficial to the development of rice cultivation technology with promotion of resource-conservation and environmental friendliness. The effects of WIP with nitrogen-reduction on population quality, annual yield and nitrogen use efficiency were studied by a field experiment. WIP could maintain or increase the annual yield of rice production models. The highest annual yield of more-water-saving irrigation practice (WIP150) was 8.42 t hm−2 for the double-season rice production model and 12.71 t hm−2 for the ratoon rice production model, respectively. Compared with non-application of nitrogen, the annual yield of nitrogen-reducing practice (NRP) and farms' fertilizer practice (FFP) increased significantly (p &lt; 0.01), while a non-significant difference of annual yield between the FFP and NRP was observed; the annual yield of the NRP and FFP was 9.73 and 10.02 t hm−2 of the double-season rice production model, and 12.84 and 14.34 t hm−2 of the ratoon rice production model, respectively. AEN, PEN, PFPN and RUEN of the NRP were higher than those of the FFP. Therefore, observing the change of water layer in the soil layer via a simple self-made PVC indicator tube, reducing about 20% nitrogen quantity was a feasible and simple cultivation technique for water-saving and nitrogen-reduction in the rice production models.</jats:p>
关键词：
Gibberellic acid;Hybrid rice;Seed vigor;Seed yield;Stigma vigor index
摘要：
Gibberellic acid (GA(3)) application after anthesis is an important practice in hybrid rice seed production, and it plays diverse roles in seed quality and seed yield. The main objective of this study was to determine (1) the effects of GA(3) application after anthesis on seed vigor and (2) the optimal GA(3) dosage applied to Indica hybrid rice seed production. Field experiments of different GA(3) dosages (15 g hm(-2) and 30 g hm(-2), respectively) after anthesis were conducted in 2016 and 2017, and seed vigor parameters, stigma vigor index, and seed yield were determined. We found that significant differences in seed vigor parameters by a standard germination test and a cool germination test were observed among different GA(3) dosages after anthesis. Compared with the water spraying treatment, the germination percentage (GP) increased by 2.5-6.3%, and the vigor index (VI) increased by 8.9-19.8% from GA(3) application after anthesis, respectively. Moreover, the stigma vigor index of the female parent was enhanced with an increasing GA(3) dosage, and there were significant increases (7.5-16.0%) between the water spraying treatment and GA(3) spraying treatments. There were positive significant relationships between the VI and stigma vigor index. Additionally, the seed yield of the GA(3) application with 30 g hm(-2) was 3.9% higher on average than that of the water spraying treatment. Therefore, our study suggests that seed vigor can be increased by GA(3) application after anthesis, and GA(3) application should be applied at a rate of 30 g hm(-2) to improve seed vigor and maintain seed yield in Indica hybrid rice seed production.
作者机构：
[郑华斌; 唐启源; 陈元伟; 李波; 张炎胜] College of Agronomy, Hunan Agricultural University, Changsha, 410128, China;[陈其敏] Yibin College of Vocational Technology, Yibin, Sichuan 644000, China
