Lianghuan Wu

Comparisons of Yield, Water Use Efficiency, and Soil Microbial Biomass as Affected by the System of Rice Intensification

To compare the effects of the system of rice intensification (SRI) on yield, water use efficiency, and microbial biomass in associated rice soils, a field experiment was conducted in 2004 at the Agriculture Experimental Farm of Zhejiang University in Zhejiang Province, China. The treatments evaluated were traditional flooding (TF) vs. SRI cultivation methods. Grain yield in the SRI treatment was 26.4% greater than that in the TF treatment, reducing water use by 461.5 mm. Compared to TF, SRI increased water use efficiency by 91.3% and irrigation water use efficiency by 194.9%. Soil microbial indicators during the rice‐growing season also diverged between TF and SRI. Microbial biomass C (MBC) was in the range of 101–196 mg kg−1 for TF vs. 113–224 mg kg−1 for SRI; microbial biomass N (MBN) was in the range of 14–33 mg kg−1 for TF vs. 28–53 mg kg−1 in SRI. Compared to TF, SRI significantly increased both MBC and MBN, regardless of sampling date.

Soil microbial biomass as affected by non-flooded plastic mulching cultivation in rice

The long-term field experiments were initiated in 2001 on five sites in Zhejiang province of China to monitor the impacts of non-flooded plastic mulching management on rice soil microbial biomass for sustainable agro-ecosystem. The three treatments were plastic film mulching with no flooding (PM), no plastic film mulching and no flooding (UM), and the traditional flooding management (TF). Microbial biomass C accounted for 0.3–2.4% of the soil total organic C, microbial biomass N for 0.79–4.3% of the soil total N, and microbial biomass P for 0.1–1.6% of the soil total P. Three years of non-flooded plastic film mulching reduced microbial biomass C and N and increased microbial biomass P in rice soil.

Nutrient uptake and water use efficiency as affected by modified rice cultivation methods with reduced irrigation

A field experiment was conducted in 2005 to investigate the effects of modified rice cultivation methods on: water use efficiency, the uptake of nutrients (N, P and K) by plants, and their distribution within plants and their internal use efficiency. The treatments were modified methods of irrigation, transplanting, weeding, and nutrient management, comparing the System of Rice Intensification (SRI) with standard rice-growing methods including traditional flooding (TF). Results showed that the uptake of N, P, and K by rice plants during their growth stages was greater with SRI management compared to TF, except during the tillering stage. At maturity stage, SRI plants had taken up more nutrients in their different major organs (leaves, stems, and sheaths; panicle axis; and seeds), and they translocated greater amount of nutrients to the grain. Under SRI, the ratio of N, P, and K in seed grain to total plant N, P, and K was 4.97, 2.00, and 3.01% higher, respectively, than with TF. Moreover, under SRI management, internal use efficiency of the three macronutrients (N, P, and K) was increased by 21.89, 19.34, and 16.96%, respectively, compared to rice plants under TF management. These measurements calibrate the crop’s physiological response to differences in cultural practices, including the maintenance of aerobic versus anaerobic environment in the root zones. With SRI, irrigation water applications were reduced by 25.6% compared to TF. Also, total water use efficiency and irrigation water use efficiency was increased with SRI by 54.2 and 90.0%, respectively. Thus, SRI offered significantly greater water saving while at the same time producing more grain yield, in these trials 11.5% more compared to TF.

Effects of iron and zinc foliar applications on rice plants and their grain accumulation and grain nutritional quality

BACKGROUND Foliar sprays of iron (Fe) and zinc (Zn) fertilisers are known to be an effective way to improve Fe and Zn concentrations in rice grain. However, results can differ significantly among different rice cultivars and/or types of foliar fertiliser. In this study, several Fe-rich rice cultivars were used to identify an effective foliar fertiliser for optimal Fe and Zn enrichment of rice grain. RESULTS Foliar Fe amino acid (Fe-AA) fertiliser significantly improved the Fe concentration in brown rice of most cultivars. Compared with the control, the average Fe concentration in all tested cultivars was increased by 14.5%. The average Fe concentration was increased by 32.5% when 1% (w/v) nicotianamine (NA) was added to Fe-AA, while the average Zn concentration was increased by 42.4% when 0.5% (w/v) ZnSO₄ · 7H₂O was added to Fe-AA. CONCLUSION The results suggested that NA at a suitable concentration added to Fe-AA fertiliser could accelerate Fe accumulation in rice grain. A relatively low concentration of ZnSO₄ · 7H₂O added to Fe-AA significantly increased Fe and Zn accumulation in rice grain. The study identified some useful foliar fertilisers for enhancing the levels of Fe and Zn in selected Fe-rich rice cultivars.

Iron and zinc biofortification in polished rice and accumulation in rice plant (Oryza sativa L.) as affected by nitrogen fertilization

Abstract With focus on maximizing grain yield in rice (Oryza sativa L.) production, especially in China, information available in the literature on how nitrogen (N) fertilization of rice crops affects biofortification of iron (Fe) and (Zn) in grains is limited. The objective of the experiment was to investigate to what degree application of N fertilizer attained the optimum Fe and Zn concentration in rice grains as well as grain yield under pot conditions. Two rice cultivars of the indica ‘Zhenong 952’ and the japonica ‘Bing 98110’, grown widely in the area of the Yangtse River Delta in southern China, and fertilized with four rates of urea (0, 0.50, 1.00 and 1.50 g N pot−1), were investigated. The results showed that, in the pot trails, the optimum application of N alone on rice crops could increase the concentration of Fe in the polished rice. By considering both health and commercial reasons, when N application reached 1.00 g pot−1, the optimal Fe and Zn concentrations were attained as well as grain yield for ‘Zhenong 952’, and for ‘Bing 98110’ the optimum N application was 1.50 g pot−1. Fe appeared not to be so easily mobilized as Zn in the plant. The ratio of Zn deposited in the brown rice was about 40% of total Zn in the plant, irrespective of N application. However, deposited Fe was only about 3% of total Fe. Fe concentration in brown rice was only about ½ that in rice husk, 1/5 that in peduncles, 1/10 that in leaves, and only a little more than 1% of that in roots. These results suggested if we wanted to increase the amount of Fe in grains the translocation mechanism of Fe in rice plant must be clearly understood first.

Can foliar iron-containing solutions be a potential strategy to enrich iron concentration of rice grains (Oryza sativa L.)?

Abstract The available literature on whether or not foliar iron (Fe)-containing solutions can be one of the sustainable and low-cost strategies to increase Fe concentration in edible portions of staple food crops consisted of a few previous studies of Fe in plants, and mainly focused on Fe-deficiency remedies. Our experiment was carried out to examine the effects of foliar Fe-containing solutions on Fe enrichment and on the nutritional, cooking, and eating qualities of polished rice of the japonica ‘Bing 98110’ planted on a powdery loam soil under pot conditions. The results showed that Fe concentration in polished rice could be enriched with foliar Fe(II)-amino acids [the main formulation was the complex of 0.1% (w/v) FeSO4 •7H2O and 0.4% (w/v) compound amino acids, 18.6% N] application. Compared with the control, Fe concentration increased significantly, by 88.0%. Meanwhile, the positive effects on Zn concentration and protein and amino acid content improvement were found with boric acid (H3BO3, B) added to Fe(II)-amino acids foliar application. In detail, Zn concentration significantly increased (19.6%), and protein and lysine were increased significantly by 30.1 and 35.1%, respectively. Also the cooking and eating qualities were improved with foliar Fe(II)-amino acids and B compound spray.

Effects of Nitrogen Application Rates on Rice Grain Yield, Nitrogen-Use Efficiency, and Water Quality in Paddy Field

Excessive nitrogen (N) fertilizer application is common in the central Zhejiang Province area, China. A three-year (2009–11) experiment was conducted to determine the optimum N application rate for this area by studying the effects of various N rates on rice (Oryza sativa L.) yield, N-use efficiency (NUE), and quality of paddy field water. Results showed that no significant yield differences were observed under N rates from 180 to 315 kg ha−1. The NUE could be improved by reducing N application rates without significantly decreasing yield. Due to high ammonia (NH4+-N) and nitrate (NO3—N) concentrations, 5–7 days after N application was a critical stage for reducing N pollution. The N rate for the greatest yield was 176 kg ha−1, accounting for 65 percent of the conventional N rate (270 kg ha−1). The N-rate reduction in this area may be necessary for maintaining high yield, improving NUE, and reducing environmental pollution.

Optimizing Weight Method to Evaluate Nitrogen Release Characters of Polymer-Coated Urea in Paddy Soil under Field Conditions

ABSTRACT Polymer-coated urea can improve nitrogen (N) use efficiency of rice. But, the nitrogen release characters from flooded paddy soil are lacking. Traditional weight methods use a vacuum oven to dry. Depending on the coating, some polymer-coated urea still retain water after drying. A new weight method was proposed: washing fertilizer granules in the buried bags with distilled water, and transferring to a plastic bag, then placing it at −80°C for 2 h, and then transferring to the lyophilizer to dry for 24 h. The method was compared with chemical analyses. This result indicated that the weight method can be used for determining N release characteristics in paddy soil. In the whole growing season, over 75% of N was released. Different amounts of granules in the bag can influence the result. The release rate of 10.0 g in bags was higher than 3.0 g. Surface applied polymer-coated urea has a higher rate than deep application.