Enhancing accumulation and translocation of soluble sugar and utilization rate of climatic resources in Japonica rice in cold region through optimized fertilization

Objectives The effects of different ratios of N, P and K fertilizers on the accumulation and translocation of soluble sugar in functional leaves, stems, sheaths and grains of Japonica Rice in cold region were studied.

Methods The “3414” fertilization scheme was used in the field experiment, and the test Japonica rice variety in the cold region was Dongnong 427. At five main growth stages from tillering to maturity, the accumulation of soluble sugar (ASS) in functional leaves, stem sheaths and grains of rice were measured, and relationships with climatic resources were determined.

Results The rice yield was significantly affected by the combined application of N, P and K fertilizers, with the highest yield in N2P2K2 treatment. Compared with N0P0K0, the ASS in aboveground organs of all fertilization treatments were significantly enhanced, with the highest ASS of functional leaves in N3P2K2 treatment before anthesis and in N2P2K2 after anthesis. The ASS in stem sheath and grain were the highest in N2P2K2 treatment at all the five growth stages. The highest transport of soluble sugar in functional leaves and stem sheath was N2P2K2 treatment after anthesis. N2P2K2 and N3P2K2 had the longest growth period. The photosynthetically active radiation (PAR), radiation utilization rate (RUE) and accumulated temperature production efficiency (TPE) of all fertilization treatments were higher than those of N0P0K0 treatment, with the highest values in N2P2K2 treatment. The ASS in different parts were significantly and positively correlated with PAR, RUE and TPE. The effect of ASS in functional leaves on PAR, RUE and TPE at tillering and booting stages was greater than those in stems and sheaths. The PAR, RUE and TPE were more affected by ASS in stem sheath at full heading stage, grain filling and mature stage than those in functional leaves. The effect of ASS on PAR, RUE and TPE in mature stage was greater than that in full heading and filling stage. The effect of soluble sugar transport from stem and sheath on PAR, RUE and TPE after anthesis was greater than that of functional leaves.

Conclusions Sufficient supply of N, P and K is effective to form rice population that efficiently capture light and temperature resources during the whole growth period of Japonica rice in cold region, and the accumulation of soluble sugar in above ground organs of Japonica rice in cold region is significantly and positively correlated with PAR, RUE and TPE. Moreover, reasonable nutrient supply chold also prolonge the days of growth period, which give longer time for soluble sugar transport from functional leaves and stem sheath to grain. The ratio of N–P–K of 150–120–80 kg/hm² (N2P2K2) in this experiment is most effective for the accumualtion and transportation of soluble sugar and use of light and tenperterture resorces throught growing stage of Japonica rice in cold region, so could achive the highest yield.