Abstract:

Rice quality can be improved through nitrogen fertilizer strategy, such as the rate and the timing of application. The establishment of “the leaf age model of development process of rice” makes rice cultivation move accurate in growth and development process modeling, cultivation diagnosis standardization and regularization of technical measures. The objective of this study was to find the suitable way of nitrogen application for improving the rice quality under the condition of the high yield. Using hybrids Kyou818 and Changyou1 planted with a total applied nitrogen amount of 225 kg/ha in the all growth stage. The different proportion of N-fertilizer at earlier and middle stages (the ratio of basic-tilling and stem- panicle fertilizer was 3:7, 5:5 and 7:3, respectively) and N-applying leaf age of stem- panicle N-fertilizers (Stage of remaining leaf primordium number 5, 3; 5, 4, 3, 2, 1; 4, 2; 3, 1, respectively) were imposed on the experiment. The results showed that with the increasing of N-application rate at earlier stages, head milled rice, protein content, setback, chalkiness and pasting temperature were decreased; gel consistency, peak viscosity and breakdown increased gradually; effect of N-fertilizer on trough viscosity and final viscosity varied with different cultivars. It suggested that the decrease of the nitrogen application proportion at middle stage improved facial features、cooking quality and viscosity of amylum, but adverse effect on milling quality and nutrient quality were found. Effect of N-applying leaf age on quality varied in different application proportions and cultivars. With decreasing proportion of N-application at middle stages, good facial features, cooking quality and viscosity of amylum were obtained by postponing the time of N-applying leaf age. Some quality indexes of Changyou 1 reached maximum (such as gel consistency, peak viscosity, trough viscosity, final viscosity and breakdown etc.) or minimum (such as chalkiness percentage, chalkiness degree and setback etc.) when the time of panicle fertilizer application was at a leafage later than that of K-you 818. This maybe attributes to Changyou 1 with long days-to-maturity. As a whole, the N-application proportion of 7:3 at earlier and middle stages could result in a good performance for quality of the two cultivars, while under this proportion, a much more good performance for quality of K-you 818 and Changyou 1 could be observed when applied stem- panicle N-fertilizers with equal amount in 4^th and 2^nd, and 3^rd and 1^st leaf age from top, respectively.

Key words: Hybrid rice, Nitrogen application, Quality, RVA