Being divided into three groups-strong, moderate and weak-according to the different kinetic parameters (Fmax, km, Cmin) of potassium uptake by crops, 21 cultivars of rice have been studied to find out the relationshi...Being divided into three groups-strong, moderate and weak-according to the different kinetic parameters (Fmax, km, Cmin) of potassium uptake by crops, 21 cultivars of rice have been studied to find out the relationships between their potassium nutrition and the oxidation-reduction status in the rhizosphere soils.Results show that, with no application of K fertilizer, there were higher contents of active reducing substances and ferrous iron in rhizosphere soils planted with cultivars, such as Zhongguo 91, week in absorbing potassium than in soils cropped with cultivars, Shanyou 64, stronger in absorbing potassium. As a result of K application, however, these toxic substances were decreased appreciably in the soil, particularly in the root zone where weakly K-absorbing cultivars were growing, and the parameter of soil redox (pH +pE) was increased, the most striking example of this being found in the rhizosphere soil where the more strongly K-absorbing cultivars were growing. On and close to the root surface in soils where rice plants were supplied with potassium fertilizer, rather more iron oxide had been accumulated compared with rice receiving no potash, and even greater amounts of red iron oxide precipitated on the rice root in neutral paddy soils. As shown by the concentration distribution of active reducing substances and ferrous iron in a microzone of the profile, the redox range of rice roots supplied with potassium may extend as far as several centimeters from the root surface. It can thus be seen that potassium nutrition exerts its effect first on the morphological properties of rice roots and their exudation of oxygen, then on the content of soluble oxygen and the count and species of oxygen-consuming microbes in the rhizosphere soil, and finally on the redox status of the soil.展开更多
A two-year on-farm study was carried out at Eglime in the moist savanna （MS） and Ouake in the dry savanna （DS） of Benin to evaluate the contribution of inoculation of dual-purpose soybean varieties to grain yield ...A two-year on-farm study was carried out at Eglime in the moist savanna （MS） and Ouake in the dry savanna （DS） of Benin to evaluate the contribution of inoculation of dual-purpose soybean varieties to grain yield of upland NERICA rice fertilized with low N level. In 2005, four dual-purpose, promiscuous soybean varieties （cv. TGx1440-IE; TG×1448-2E; TG×1019-2EB; and TG×1844-18E）, and a popular improved variety （cv. Jupiter） were sown in 12 farmer fields with and without Bradyrhizobium japonicum inoculation. There was also land which was left fallow that acted as the control. In 2006, upland interspecific rice （NERICA 1） was sown in all the plots and supplied with 15 kg N haL. Dry matter yield, N accumulation, and net N-balance were significantly enhanced by over 40% with inoculation of cv. TG× 1844-18E than non-inoculation in the DS in comparison to other cultivars. There were no significant effects of inoculation of previous soybean cultivars on soybean grain yield and on the succeeding NERICA rice yield. Averaged over inoculation, previous cv. TG× 1019-2EB plots supplied with only 15 kg N hal gave the highest grain yield, more than twice the yield of control plots in the DS, possibly because of significant production of higher tillers, panicles and harvest index than the other cultivars; and it could be recommended for upland rice-based system for NERICA production.展开更多
Small-scale household agricultural production has been in conflict with China＇s agricultural modernization.In the context of vigorously promoting rural land circulation and moderate scale management nationwide,resear...Small-scale household agricultural production has been in conflict with China＇s agricultural modernization.In the context of vigorously promoting rural land circulation and moderate scale management nationwide,research on the relationship between farm size and scale efficiency has become increasingly important.In this paper,we use the ＂DEA-OLS＂ two stage method to analyze data from 368 surveys of rice farming households in the Jianghan Plain.The scale efficiency of rice farming was calculated,and the relationship between farm size and scale efficiency investigated.The results indicate that（1） the rice farm size is generally small in Jianghan Plain,with an average of 0.77 ha.The average scale efficiency is 0.88,and it is the main factor limiting an increase in comprehensive technical efficiency.Moreover,88.32% of households are in the stage of increasing returns to scale.（2） There is a stable inverted ＂U＂ type relationship between rice farm size and scale efficiency.Considering characteristics of the householder,the household and land quality,the maximum scale efficiency corresponds to a household with 5 ha of rice farm.（3） Among householder characteristics,age has a significant negative influence on scale efficiency,and scale efficiency is lower for a household whose householder is engaged in non-farm work than for one whose householder is devoted to farming.As for land quality,there was a significant positive effect of irrigation on scale efficiency.Among family characteristics,the application of a machine during the seeding process increased scale efficiency by 3.07%.Therefore,we suggest that local government should actively promote rural land circulation,implement a staged-scale management subsidy,and other forms of support for the purchase of agricultural machinery and technical popularization.Increased investment in irrigation improvements and mechanical facilities and encouragement of farmers to enlarge their farm size could improve scale efficiency and farming profit and lead to the development of moderate scale management.展开更多
文摘Being divided into three groups-strong, moderate and weak-according to the different kinetic parameters (Fmax, km, Cmin) of potassium uptake by crops, 21 cultivars of rice have been studied to find out the relationships between their potassium nutrition and the oxidation-reduction status in the rhizosphere soils.Results show that, with no application of K fertilizer, there were higher contents of active reducing substances and ferrous iron in rhizosphere soils planted with cultivars, such as Zhongguo 91, week in absorbing potassium than in soils cropped with cultivars, Shanyou 64, stronger in absorbing potassium. As a result of K application, however, these toxic substances were decreased appreciably in the soil, particularly in the root zone where weakly K-absorbing cultivars were growing, and the parameter of soil redox (pH +pE) was increased, the most striking example of this being found in the rhizosphere soil where the more strongly K-absorbing cultivars were growing. On and close to the root surface in soils where rice plants were supplied with potassium fertilizer, rather more iron oxide had been accumulated compared with rice receiving no potash, and even greater amounts of red iron oxide precipitated on the rice root in neutral paddy soils. As shown by the concentration distribution of active reducing substances and ferrous iron in a microzone of the profile, the redox range of rice roots supplied with potassium may extend as far as several centimeters from the root surface. It can thus be seen that potassium nutrition exerts its effect first on the morphological properties of rice roots and their exudation of oxygen, then on the content of soluble oxygen and the count and species of oxygen-consuming microbes in the rhizosphere soil, and finally on the redox status of the soil.
文摘A two-year on-farm study was carried out at Eglime in the moist savanna （MS） and Ouake in the dry savanna （DS） of Benin to evaluate the contribution of inoculation of dual-purpose soybean varieties to grain yield of upland NERICA rice fertilized with low N level. In 2005, four dual-purpose, promiscuous soybean varieties （cv. TGx1440-IE; TG×1448-2E; TG×1019-2EB; and TG×1844-18E）, and a popular improved variety （cv. Jupiter） were sown in 12 farmer fields with and without Bradyrhizobium japonicum inoculation. There was also land which was left fallow that acted as the control. In 2006, upland interspecific rice （NERICA 1） was sown in all the plots and supplied with 15 kg N haL. Dry matter yield, N accumulation, and net N-balance were significantly enhanced by over 40% with inoculation of cv. TG× 1844-18E than non-inoculation in the DS in comparison to other cultivars. There were no significant effects of inoculation of previous soybean cultivars on soybean grain yield and on the succeeding NERICA rice yield. Averaged over inoculation, previous cv. TG× 1019-2EB plots supplied with only 15 kg N hal gave the highest grain yield, more than twice the yield of control plots in the DS, possibly because of significant production of higher tillers, panicles and harvest index than the other cultivars; and it could be recommended for upland rice-based system for NERICA production.
基金National Natural Science Foundation of China(41571095)
文摘Small-scale household agricultural production has been in conflict with China＇s agricultural modernization.In the context of vigorously promoting rural land circulation and moderate scale management nationwide,research on the relationship between farm size and scale efficiency has become increasingly important.In this paper,we use the ＂DEA-OLS＂ two stage method to analyze data from 368 surveys of rice farming households in the Jianghan Plain.The scale efficiency of rice farming was calculated,and the relationship between farm size and scale efficiency investigated.The results indicate that（1） the rice farm size is generally small in Jianghan Plain,with an average of 0.77 ha.The average scale efficiency is 0.88,and it is the main factor limiting an increase in comprehensive technical efficiency.Moreover,88.32% of households are in the stage of increasing returns to scale.（2） There is a stable inverted ＂U＂ type relationship between rice farm size and scale efficiency.Considering characteristics of the householder,the household and land quality,the maximum scale efficiency corresponds to a household with 5 ha of rice farm.（3） Among householder characteristics,age has a significant negative influence on scale efficiency,and scale efficiency is lower for a household whose householder is engaged in non-farm work than for one whose householder is devoted to farming.As for land quality,there was a significant positive effect of irrigation on scale efficiency.Among family characteristics,the application of a machine during the seeding process increased scale efficiency by 3.07%.Therefore,we suggest that local government should actively promote rural land circulation,implement a staged-scale management subsidy,and other forms of support for the purchase of agricultural machinery and technical popularization.Increased investment in irrigation improvements and mechanical facilities and encouragement of farmers to enlarge their farm size could improve scale efficiency and farming profit and lead to the development of moderate scale management.
