| Ratoon rice production employs the ability of rice plants to regenerate new tillers after harvest.It is a viable option for farmers where a second rice crop is not feasible and upland crops are either not profitable or cannot be grown due to poor drainage.Ratoon rice has 50-60%reduction in labor with respect to harvest of the first rice crop and transplanting the second.It is a practical way to increase rice production,with the actual planting area of 0.5 ha and potential area of 3.3 M ha in southern China.However,it has lower yield,being 2 t/ha,due to poor management of water as well as short growth period and soil sterility.The study aims to explore the physiol-ecological foundation of high quality and WUE of Ratoon rice at Longchang in Southeast Sichuan,the main production area of ratoon rice plantation in China.Twelve typical paddy fields of mountain and hill areas were selected,and seven cultivars of hybrid rice were used to compare the differences in quality traits between reatooning rice and its parent rice.In addition,Based on the daily data at six meteorological stations including Suining,Neijiang,Luzhou,Yibin,Naxi and Xuyong during 1951-2007,the FAO Penman-Monteith formula and the method of crop coefficient calculation were used to estimate the water requirements of ratoon rice for the period of sprouting of axillary bud(from late July to mid August)and the spatial and temporal distribution characteristics of precipitation and crop water requirement for the period of sprouting of axillary bud were explored.The main results are obtained as follows:(1)There is a significant differences of yield and yield components between main season and ratoon season.The number of ratooning rice panicle,seeding setting rate,grain weight and yield were lower than the main crop,while the effective panicle number was significantly higher than the main season.Grain yield of ratoon rice was lower than main season because of smaller sink size.Regarding grain quality,ratoon rice was superior to main crop.The milled rice rate and the head rice rate of ratoon season gain was significantly higher than that of main season.The protein components including albumin,globulin,gliadin and glutenin of ratoon rice were lower than those in the main crop,while the amylose higher.(2)Comparing minerals in leaves and brown rice between main season and ratoon season,it was found that the contents of Ca,Na and Mg in leaves from main rice were higher than ratoon rice.However,they showed opposite trend for brown rice.The content of Fe,Zn and Cu in leaves from ratoon rice were higher,while the content of Mn lower.The contents of Fe and Cu in brown rice from ratoon rice were visibly higher than those of the main crop,while Zn and Mn lower.Therefore,the lack of N accumulation,Ca,Na and Mg transport and Mn accumulation may be physiological mechanism of low seed setting rate of ratoon rice.(3)Combined with the spatial distribution characteristics of precipitation and crop water requirement,the water-meeting situation of ratoon rice during the sprouting of axillary bud period were analyzed.The results showed that the mean annual precipitation during sprouting of axillary bud were 156.7mm,175.4mm,168.5mm,66.7mm,227.5mm,and 153.4mm,and annual crop water requirement were 141.5mm,138.6mm,144.5mm,146.0mm,128.5mm,and 142.7mm for Suining,Neijiang,Luzhou,Yibin,Naxi and Xuyong,respectively.In terms of the congruence between rainfall and the crop water requirement,Yibin,Neijiang,Luzhou and Xuyong are suitable for ratoon rice,while Naxi is not suitable.Temporal distribution of precipitation and crop water requirement for the period of sprouting of axillary bud was evaluated by calculating the ratio of rainfall(R)to ETc.For Neijiang,63%years from 1951 to 2007 had a R/ETc ratio above 1.0,and 12%below 0.5.For Luzhou,52%years were above 1.0,whereas 4%below 0.5.Thus Neijiang is vulnerable to drought stress during sprouting of axillary period. |
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