- [Show abstract] [Hide abstract] ABSTRACT: In the present study, different drought tolerance rice from different countries and areas were selected and grown in water field and drought field respectively, including 4 traditional varieties of drought rice, 18 varieties of modified drought rice, 2 varieties of drought traits rice, 2 varieties of drought tolerance rice, and a total of 30 different varieties of drought tolerance rice were involved. Using near infrared diffuse reflection spectra of leaves from water field and drought field, we studied the rice drought tolerance identification analysis. Results showed that: using the average spectra of several leaves' spectra, selecting 4,500-7,500 cm(-1) as effective analysis spectra zone, choosing the first derivative and multiple scattering correction (MSC) as spectra preprocessing method, we can set up the calibration models between the spectra of leaves from drought field and the yield of rice. Simultaneously, we concluded that the performance of calibration model for rice yield and drought tolerance identification indexes in the upper booting stage was better than in the previous booting stage whose correlation coefficient of cross validation could reach 0.8. But there was no obvious relation between the spectra from water field and the yield, the drought tolerance identification indexes. We explained the difference in these two series models' performance from the relationship between some parameter of the leaves' biochemistry (chlorophyll, moisture, etc) and yield, the drought tolerance identification indexes.
- [Show abstract] [Hide abstract] ABSTRACT: Aerobic rice is a new production system in which specially-developed varieties are grown under non-flooded, non-puddled, and non-saturated soil conditions. In 2003-2004, irrigation x Nitrogen experiments were carried out near Beijing using variety HD297. Water treatments included four irrigation levels, and Nitrogen treatments included different fertilizer N application rates and different numbers of N splits. The highest yields were 4 460 kg/ha with 688 mm of total (rain plus irrigation) water input in 2003 and 6 026 kg/ha with 705 mm of water input in 2004. Because of the quite even distribution of rainfall in both years, the four irrigation treatments did not result in large differences of soil water conditions. There were few significant effects of irrigation on biomass accumulation, but yield increased with the total amount of water applied. High yields coincided with high harvest index and high percentages of grain filling. The application of fertilizer N either reduced biomass and yield or kept it at the same level as 0 N and consistently reduced the percentage grain filling and 1 000-grain weight. With the highest water application, five splits of N gave higher yield than three splits, whereas three splits gave higher yield than five splits with lower water applications.
- [Show abstract] [Hide abstract] ABSTRACT: Aerobic rice has been considered a promising rice cultivation system as water scarcity is increasing in the world. This article summarizes the advances in aerobic rice management researches in the North China Plain, focusing on yield formation and its bottleneck. High-yielding and good-quality aerobic rice varieties adapted to aerobic soil conditions have been released officially and adopted by farmers in North China. The varieties Handao 502 and Handao 297 have been recognized as the most promising varieties reaching a yield level ranging 3.5-5.0 t ha−1 with 450-650 mm water input. Compared with lowland rice, water input in aerobic rice was more than 50% lower, and water productivity was 60% higher. Researches on responses of rice cultivars to nitrate nitrogen (N) and ammonium N supplied at early growth stages provided the first evidence for a preference of aerobic rice HD297 for nitrate N supply, compared with the lowland rice variety. Zinc uptake studies demonstrated that introduction of aerobic rice system on calcareous soils may increase zinc deficiency problems. Sink size was identified as the limitation of aerobic rice yield, because its spikelet number m−2 was too low (20 000-24 000) compared with the lowland rice. For future research, more attention is suggested to be paid to yield formation focusing on effects of water regimes on tiller dynamics. Understanding of nutrient uptake and response to fertilization effects are also urgently required to establish optimized crop management technology. Additionally, alternative cropping systems based on aerobic rice should be established, and key sustainability and environmental impact issues in the systems need to be identified.
China Agricultural University
Peping, Beijing, China
- College of Agronomy and Biotechnology