Effect of Panicle Fertilizer Amounts on the Yield and Population Quality of Indica Directly Sowing Rice under Potato-rice Rotation System

PurposeIn order to achieve the goals of reducing fertilizer without reducing yield, saving cost, increasing efficiency and reducing environmental pollution. We explored a new method of high yield and high efficiency fertilization for directly sowing rice under winter potato-rice rotation system in the humidity indica subzone of Yunnan Province.

MethodField experiments were conducted in a plot of former planting winter potato in Shuangjiang County, Lingcang City, Yunnan Province. Using indica hybrid rice Fyou 498 and Longliangyou 1206 as materials. On the basis of no basal and tillering fertilizer, four panicle fertilizer amounts 0, 60, 90 and 120 kg/hm² (expressed as N₀, N₁, N₂ and N₃, respectively) were topdressed as spikelet-promoting and spikelet-sustaining fertilizer in weight ratio of 1∶1. To investigate the effects of panicle fertilizer amount application on the population quality, photosynthetic characteristics and yield of indica hybrid rice.

ResultThere was no significant difference in tiller number between the two cultivars before the application of spikelet-sustaining fertilizer (P>0.05); but after the application of spikelet-sustaining fertilizer, the extinction rate of tillers could be slowed down, and the productive tiller rate and effective panicle number could be increased significantly (P<0.05). Panicle fertilizer could significantly reduce relative leaf color difference between the inverse third leaf and inverse fourth leaf (P<0.05), significantly increase of leaf area index, effective leaf area index, grain number per panicle and total spikelet number (P<0.05), at the same time significantly increase photosynthetic characteristic parameters (P<0.05), such as the net photosynthetic rate, intercellular carbon dioxide concentration, stomatal conductance and transpiration rate, promote dry matter accumulation in full heading stage, mature stage and after full heading. Application panicle fertilizer amount of 60, 90 and 120 kg/hm² to promote Fyou 498 yield by 12.10%, 19.33% and 17.34%, respectively, and Longliangyou 1206 yield by 12.15%, 19.35% and 7.88%, respectively. Two varieties under panicle fertilizer amount of 90 kg/hm² got the highest yield, Fyou498 was 10.36 t/hm², and Longliangyou 1206 was 9.52 t/hm². The maximum yield was achieved by increasing effective panicle and spikelet number per panicle, obtaining high total spikelet number and maintaining high grain setting rate and 1 000-grain weight. The agronomic efficiency of Fyou 498 and Longliangyou 1206 increased to 18.65 and 17.15 kg/kg, respectively under the optimal panicle fertilizer amount of 90 kg/hm².

ConclusionThe former crop was winter potato high foundation fields in Yunnan Province, no basal and tillering fertilizer were applied in the early stage, combined with field drying to control peak tillers, prompting ineffective tillering stage leaf color yellow, applying 45 kg/hm² of pure nitrogen as panicle fertilizer to the inverse fourth leaf and the inverse second leaf can respectively reduce death rate of tillers, increase the effective panicles, promote the formation of big panicle, and thus achieve high yield.