| Japonica Rice is the major cultivated rice subspecies in China, accounting for over25.5%of the total rice growing area. Jiangsu province is the main base for the production of rice in China, the planting area of240×104hm2and the yield per unit area over7500kg-hm"2since1994. Jiangsu province has adjusted the structural of rice cultivars and makes Japonica rice area reached more than80%. Nowadays, Japonica rice has become the rice planting and rice consumption occupies a principal position in Jiangsu province. Jianghuai area is the most important base of Japanica rice cropping region in Jiangsu province, since the alteration of rice cropping from Indica rice to Japanica rice in1990s. Therefore, to study the improvement trends of rice yield, rice quality and mineral element concentrations in grain will be benefits to rice variety breeding in Jianghuai area.To study different levels of nitrogen fertilizer influence on rice yield, rice quality and mineral element concentrations in grain, to provide important reference for cultivation technology of high yield, high quality in rice planted. Therefore, on field experiment was conducted with three N treatment levels in2009. Our objectives were to study the improvement trends of rice yield, grain quality and mineral element concentrations in grain in Jianghuai area. The main conclusions are as follows:1. Along with rice varieties of succession, the tillering ability of rice decreased, while the bearing tiller increased. Before heading stage, the biomass decreased firstly and then increased, the minimum biomass was in the1980s, but from heading stage to maturation stage, the biomass increased. The harvest index, which was highest in the1980s varieties, showed a parabolic trend. On the basis of economic yield equivalent to biomass multiply by harvest index, the higher yield of varieties after1970than varieties in1960s was because the higher harvest index and higher biomass from heading stage to maturation stage。As regards to yield components, spike number, which was highest in the1980s, showed a parabolic trend; Seed setting are tending to increase; Thousand-grain weight in the1970s,1990s and2000s varieties was significantly greater than1960s and1980s. The above result indicated that1960s and1970s varieties achieve high yield due to higher spike number, seed setting and greater thousand-grain weight, while1980s varieties were due to higher spike number and seed setting, however,1990s and2000s varieties were because of higher grain per-spike, seed setting and greater thousand-grain weight. Increasing N supply increased rice tillering ability which was enhanced more in1980s,1990s and2000s varieties than in the1960s and1970varieties in the high N treatment. When the N supply was increased, the biomass of heading stage increased, and the1960s and1970s varieties increased more than the varieties of1980s,1990s and2000s. The biomass of varieties before1980s decreased from heading stage to maturation stage along with increasing N supply. The yield of all the varieties inceased by increasing N supply, but the1980s,1990s and2000s varieties enhanced more than the1960s and1970varieties. In the yield components, spike number and thousand-grain weight, which were all significantly difference among the N treatments, were most sensitive to N application. Seed setting was significantly lower in high N treatment than in CK. The effect of N fertilizer on grain per-spike, and spike length were not obvious.2. Grain quality indicators of brown rice rate increased along with rice varieties of succession, but milled rate decreased, head rice rate increased first and then decreased and the biggest is1970s. Chalkiness character can be improved, the chalky grain rate and chalkiness is significantly. Length-width ratio was significantly higher than that other times in1960s, from1970s to1990s showed increase tendency, the minimum was in the2000s. The protein content and amylose content had similar results with length-width ratio, but proteins content changed significantly along with rice varieties of succession. Peak viscosity increased, cool viscosity and setback decreased. The application of nitrogenous fertilizer inhibited the milling quality, but appearance quality can be improved. Amylase content deceased, but protein content increased by nitrogenous fertilizer application. Cool viscosity and setback decreased with along nitrogen application, but difference not remarkable. 3. Some mineral concentrations (P, Mg, Zn, Fe, Cu) of rice increased first and then decreased and the biggest is1990s along with rice varieties of succession; Mn concentrations has a similar results, but the biggest is1970s; Ca concentrations are the different changing trends because the different nitrogenous fertilizer application. Some mineral concentrations (P, Mg, Ca, Zn, Fe,) of brown rice increased first and then decreased and the biggest is1990s along with rice varieties of succession, Mn and Cu concentrations are the different changing trends because the different nitrogenous fertilizer application. P, Zn, Mn accumulation of5times rice was inhibited by nitrogenous fertilizer application, but Cu concentrations increased. In addition to the1990s, Mg, Ca, Fe accumulation was inhibited by nitrogenous fertilizer application. P, Mg, Ca, Zn accumulation of5times brown rice was inhibited by nitrogenous fertilizer application; Fe, Mn, Cu was the different influence to nitrogen fertilizer because the different rice varieties. So, the most of the accumulation of mineral elements in rice improve along with rice varieties of succession, but the most of the accumulation of mineral elements in rice inhibit because nitrogen fertilizer.4. Along with rice varieties of succession, the nitrogen content of rice plants is a little change in the control treatment (CK), but it’s downward trend in the nitrogen treatment, except for the1980s. Along with rice varieties of succession, the accumulated nitrogen of all varieties rice was downward trend in the control treatment (CK), and it have a similar trend in1960s,1970s,1980s and1990s in the nitrogen treatment, but the opposite for in the2000s. The nitrogen harvest index and nitrogen partial productivity changes are relatively obvious along with rice varieties of succession. The nitrogen harvest index present parabolic trend, and1980s,1990s and2000s than the1960s and1970s; the nitrogen partial productivity increase gradually, and in2000s is the largest. The nitrogen content and accumulated nitrogen of rice increased along with the increase of N application amount, but the nitrogen use efficiency decline. |
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