Nitrogen （N） use efficiency is usually less than 50%, and it remains a major problem in rice cultivation. Controlled release fertilizer （CRF） technology is one of the well-known efforts to overcome this problem. T...Nitrogen （N） use efficiency is usually less than 50%, and it remains a major problem in rice cultivation. Controlled release fertilizer （CRF） technology is one of the well-known efforts to overcome this problem. The efficiency of CRF, however, is very much dependent on the timing of nutrient release. This study was conducted to determine the precise time of N uptake by rice as a guideline to develop efficient CRF. Fertilizer N uptake by rice at different growth stages was investigated by using 15N isotopic technique. Rice was planted in pots, with 15N urea as N source at the rate of 120 kg/hm2. Potassium and phosphorus were applied at the same rate of 50 kg/hm2. Standard agronomic practices were employed throughout the growing periods. Rice plants were harvested every two weeks until maturation at the 14th week and analyzed for total N and 15N content. Nitrogen derived from fertilizer was calculated. Total N uptake in plants consistently increased until the 11th week. After that, it started to plateau and finally declined. Moreover, N utilization by rice plants peaked at 50%, which occurred during the 11th week after transplanting. N derived from fertilizer in rice plants were in the range of 18.7% to 40.0% in all plant tissues. The remaining N was derived from soil. Based on this study, N release from CRF should complete by the 11th week after planting to ensure the maximum fertilizer N uptake by rice plants. Efficient CRF should contribute to higher N derived from fertilizer which also resulted in a higher total N uptake by rice plants, increasing the potential of rice to produce higher yield while at the same time of reducina loss.展开更多
A glasshouse experiment was conducted to determine the effects of elemental sulfur(S)applications on soil acidity,the solubility of soil iron,and the uptake of iron(Fe)by corn(Zea mays L.).Soil samples were treated wi...A glasshouse experiment was conducted to determine the effects of elemental sulfur(S)applications on soil acidity,the solubility of soil iron,and the uptake of iron(Fe)by corn(Zea mays L.).Soil samples were treated with four rates of sulfur and incubated for 0,20,and 40 days before corn plantation.While one unit increase in S application rate corresponded to a soil pH decrease of approximately 1.52 units,the solubility of the Fe was significantly increased.Fe concentrations in leaves and stems increased as soil pH decreased from 7.03 to 5.42,but further soil acidification decreased Fe concentrations in plant tissues.Overall,applying S at a rate of 0.5 g S kg-1 soil may to enhance corn performance by 45 percent while posing minimal risk to groundwater or crops.展开更多
基金Long-Term Research Grant Scheme of the Ministry of Education, Malaysia under the project ‘One BAJA: The Next Generation Green and Economical Urea’
文摘Nitrogen （N） use efficiency is usually less than 50%, and it remains a major problem in rice cultivation. Controlled release fertilizer （CRF） technology is one of the well-known efforts to overcome this problem. The efficiency of CRF, however, is very much dependent on the timing of nutrient release. This study was conducted to determine the precise time of N uptake by rice as a guideline to develop efficient CRF. Fertilizer N uptake by rice at different growth stages was investigated by using 15N isotopic technique. Rice was planted in pots, with 15N urea as N source at the rate of 120 kg/hm2. Potassium and phosphorus were applied at the same rate of 50 kg/hm2. Standard agronomic practices were employed throughout the growing periods. Rice plants were harvested every two weeks until maturation at the 14th week and analyzed for total N and 15N content. Nitrogen derived from fertilizer was calculated. Total N uptake in plants consistently increased until the 11th week. After that, it started to plateau and finally declined. Moreover, N utilization by rice plants peaked at 50%, which occurred during the 11th week after transplanting. N derived from fertilizer in rice plants were in the range of 18.7% to 40.0% in all plant tissues. The remaining N was derived from soil. Based on this study, N release from CRF should complete by the 11th week after planting to ensure the maximum fertilizer N uptake by rice plants. Efficient CRF should contribute to higher N derived from fertilizer which also resulted in a higher total N uptake by rice plants, increasing the potential of rice to produce higher yield while at the same time of reducina loss.
文摘A glasshouse experiment was conducted to determine the effects of elemental sulfur(S)applications on soil acidity,the solubility of soil iron,and the uptake of iron(Fe)by corn(Zea mays L.).Soil samples were treated with four rates of sulfur and incubated for 0,20,and 40 days before corn plantation.While one unit increase in S application rate corresponded to a soil pH decrease of approximately 1.52 units,the solubility of the Fe was significantly increased.Fe concentrations in leaves and stems increased as soil pH decreased from 7.03 to 5.42,but further soil acidification decreased Fe concentrations in plant tissues.Overall,applying S at a rate of 0.5 g S kg-1 soil may to enhance corn performance by 45 percent while posing minimal risk to groundwater or crops.
