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1.
Farmers in the inland valleys of northern Ghana are challenged with nitrogen (N) deficiency as a major production constraint of rainfed lowland rice (Oryza sativa L.). With extremely low use of external inputs, there is a need to efficiently use the systems' internal resources such as native soil N. Largest soil nitrate‐N losses are expected to occur during the transition between the dry and wet season (DWT) when the soil aeration status changes from aerobic to anaerobic conditions. Technical options avoiding the build‐up of nitrate are expected to reduce N losses and may thus enhance the yield of rice. A field study in the moist savanna zone of Ghana assessed the in situ mineralization of native soil N, the contribution of nitrate to the valley bottom by sub‐surface flow from adjacent slopes, and the effects of crop and land management options during DWT on seasonal soil Nmin dynamics and the yield of lowland rice. Large amounts of nitrate accumulated during DWT with a peak of 58 kg ha−1 in lowland soils, of which 32 kg ha−1 were contributed from the adjacent upland slope. Most of this nitrate disappeared at the onset of the wet season, possibly by leaching and denitrification upon soil flooding. While the incorporation of rice straw (temporary immobilization of soil N in the microbial biomass) had little effect on soil N conservation, growing a crop during DWT conserved 22–27 kg of soil N ha−1 in the biomass and Crotalaria juncea supplied an additional 43 kg N ha−1 from biological N2 fixation. Farmers' practice of bare fallow during DWT resulted in the lowest rice grain yield that increased from 1.3 (2.2) to 3.9 t ha−1 in case of the transition‐season legume. Growing a pre‐rice legume during DWT appears a promising option to manage N and increase lowland rice yields in the inland valleys of northern Ghana.  相似文献   

2.
Background : Rice production in low‐input systems of West Africa relies largely on nitrogen supply from the soil. Especially in the dry savanna agro‐ecological zone, soil organic N is mineralized during the transition period between the dry and the wet seasons. In addition, in the inland valley landscape, soil N that is mineralized on slopes may be translocated as nitrate into the lowlands. There, both in‐situ mineralized as well as the laterally translocated nitrate‐N will be exposed to anaerobic conditions and is thus prone to losses. Aim : We determined the dynamics of soil NO3‐N along a valley toposequence during the dry‐to‐wet season transition period and the effects of soil N‐conserving production strategies on the grain yield of rainfed lowland rice grown during the subsequent wet season. Methods : Field experiments in Dano (Burkina Faso) assessed during two consecutive years the temporal dynamics and spatial fluxes of soil nitrate along a toposequence. We applied sequential and depth‐stratified soil nitrate analysis and nitrate absorption in ion exchange resin capsules in lowlands that were open to subsurface interflow and in those where the interflow from the was intercepted. During one year only we also assessed the effect of pre‐rice vegetation on conserving this NO3‐N as well as on N addition by biological N2 fixation in legumes using δ15N isotope dilution. Finally, we determined the impact of soil N fluxes and their differential management during the transition season on growth, yield and N use of rainfed lowland rice. Results : Following the first rainfall event of the season, soil NO3‐N initially accumulated and subsequently decreased gradually in the soil of the valley slope. Much of this nitrate N was translocated by lateral sub‐surface flow into the valley bottom wetland. There, pre‐rice vegetation was able to absorb much of the in‐situ mineralized and the laterally‐translocated soil NO3‐N, reducing its accumulation in the soil from 40–43 kg N ha?1 under a bare fallow to 1–23 kg N ha?1 in soils covered by vegetation. Nitrogen accumulation in the biomass of the transition season crops ranged from 44 to 79 kg N ha?1 with a 36–39% contribution from biological N2 fixation in the case of legumes. Rice agronomic performance improved following the incorporation as green manure of this “nitrate catching” vegetation, with yields increasing up to 3.5 t ha?1 with N2‐fixing transition seasons crops. Conclusion : Thus, integrating transition season legumes during the pre‐rice cropping niche in the prevailing low‐input systems in inland valleys of the dry savanna zone of West Africa can temporarily conserve substantial amounts of soil NO3‐N. It can also add biologically‐fixed N, thus contributing to increase rice yields in the short‐term and, in the long‐term, possibly maintaining or improving soil fertility in the lowland.  相似文献   

3.
Long-term effect of mungbean inclusion in lowland rice-wheat and upland maize-wheat systems on soil carbon (C) pools, particulate organic C (POC), and C-stabilization was envisaged in organic, inorganic and without nutrient management practices. In both lowland and upland systems, mungbean inclusion increased very-labile C (Cfrac1) and labile C (Cfrac2) in surface soil (0–0.2 m). Mungbean inclusion in cereal-cereal cropping systems improved POC, being higher in lowland (107.4%). Lowland rice-based system had higher passive C-pool (11.1 Mg C ha?1) over upland maize-based system (6.6 Mg C ha?1) indicating that rice ecology facilitates the stabilization of passive C-pool, which has longer persistence in soil. Organic nutrient management (farmyard manure + full crop residue + biofertilizers) increased Cfrac1 and carbon management index (CMI) over inorganic treatment. In surface soil, higher CMI values were evident in mungbean included cropping systems in both lowland and upland conditions. Mungbean inclusion increased grain yield of cereal crops, and yield improvement followed the order of maize (23.7–31.3%) > rice (16.9–27.0%) > wheat (lowland 7.0–10.7%; upland 5.4–16.6%). Thus, the inclusion of summer mungbean in cereal-cereal cropping systems could be a long-term strategy to enrich soil organic C and to ensure sustainability of cereal-cereal cropping systems.  相似文献   

4.
Alarming climate change, rainfed upland farming, and low resource-use efficiency of conventional fertilizer management practices are major production constraints detrimental to rice productivity in the northwestern (NW) Himalayas. Recent agronomic intervention of direct-seeded rice (DSR) coupled with suitable rice germplasm well suited to rainfed upland ecosystems in combination with appropriate integrated nutrient-management (INM) technology can enhance the rice productivity in the region. Thus, a field experiment with seven treatments replicated three times in a randomized block design was conducted on INM technology in rainfed upland rice cv. HPR-1156 (Sukaradhan-1) to harness the potential of DSR technology in order to boost rice productivity in the NW Himalayas. Results on INM in direct-seeded upland rice revealed that nitrogen, phosphorus, and potassium (NPK) at 90:45:45 kg ha?1 + farm yard manure (FYM) at 5 t ha?1 (oven dry-weight basis) significantly resulted in the greatest magnitude of growth and development (plant height, tillers m?2) and yield-contributing characters (panicles m?2, panicle length, grains panicle?1 and 1000-grain weight), resulting in significantly greatest grain, straw, and biological yield followed by sole use of NPK at 90:45:45 kg ha?1 and NPK at 60:30:30 kg ha?1 + FYM at 5 t ha?1, respectively, in rainfed upland rice. Application of NPK at 90:45:45 kg ha?1 + FYM at 5 t ha?1 again resulted in significant improvement in soil organic carbon and available NPK status over other treatments and initial soil fertility status in an acidic Alfisol. Overall, it is inferred that INM technology with judicious use of NPK at 90:45:45 kg ha?1 + FYM at 5 t ha?1 in rainfed upland rice under DSR technology can enhance the rice productivity and resource-use efficiency in NW Himalayas.  相似文献   

5.
The rice–wheat cropping system (RWCS), producing about 5–10 Mg ha–1 y–1 of grain, is the backbone of food‐crop production in South‐East Asia. However, this system shows signs of fatigue as indicated by declining yields, negative nitrogen (N) balances, and reduced responses to applied fertilizer at some research centers. The return of rice and wheat residues can recycle up to 20%–30% of the N absorbed by the crops. However, their wide C : N ratio can temporarily immobilize native and applied N. To overcome this immobilization, wheat‐straw application was supplemented with the incorporation of Sesbania green manure and mungbean residues, and their effects on productivity, agronomic N efficiency, and system's apparent N balances were studied. Combining the application of wheat straw with Sesbania green manure or mungbean residues increased cereal grain yield and agronomic N efficiency and improved the generally negative apparent N balances. The combined use of wheat straw and mungbean produced an additional 0.5–0.6 t ha–1 protein‐rich grain and thus appears to be the most promising residue‐management option for rice–wheat cropping systems in South Asia, provided that the transition cropping season between wheat harvest and rice transplanting is long enough.  相似文献   

6.
A field experiment was conducted for 3 crop years (July‐June) at the Indian Agricultural Research Institute, New Delhi to study the effects of Sesbania and cowpea green manuring (GM) and incorporation of mungbean residues after harvesting grain, Leucaena loppings, FYM and wheat straw incorporation before planting rice and application of 0,40,80 and 120 kg N ha?1 to rice on the soil organic carbon (SOC), alkaline permanganate oxidizable N (APO‐N), 0.5 M sodium bicarbonate extractable P (SBC‐P) and 1N ammonium acetate exchangeable K (AAE‐K) in surface 0–15 cm soil after the harvest of rice and wheat grown in sequence. Green manuring and addition of organic residues prevented the decline in SOC. On the other hand addition of N fertilizer tended to decrease SOC after rice harvest. On the contrary application of green manures, organic residues, FYM and fertilizer N increased APO‐N, which indicates the benefit of these treatments to a more labile soil organic N pool. Also application of green manures, organic residues, FYM and fertilizer N increased SBC‐P. Not much change was observed in AAE‐K by the treatments applied.  相似文献   

7.
Productivity of rainfed finger millet in semiarid tropical Alfisols is predominantly constrained by erratic rainfall, limited soil moisture, low soil fertility, and less fertilizer use by the poor farmers. In order to identify the efficient nutrient use treatment for ensuring higher yield, higher sustainability, and improved soil fertility, long term field experiments were conducted during 1984 to 2008 in a permanent site under rainfed semi-arid tropical Alfisol at Bangalore in Southern India. The experiment had two blocks—Farm Yard Manure (FYM) and Maize Residue (MR) with 5 fertilizer treatments, namely: control, FYM at 10 t ha?1, FYM at 10 t ha?1 + 50% NPK [nitrogen (N), phosphorus (P), potassium (K)], FYM at 10 t ha?1 + 100% NPK (50 kg N + 50 kg P + 25 kg K ha?1) and 100% NPK in FYM block; and control, MR at 5 t ha?1, MR at 5 t ha?1 + 50% NPK, MR at 5 t ha?1 + 100% NPK and 100% NPK in MR block. The treatments differed significantly from each other at p < 0.01 level of probability in influencing finger millet grain yield, soil N, P, and K in different years. Application of FYM at 10 t ha?1 + 100% NPK gave a significantly higher yield ranging from 1821 to 4552 kg ha?1 with a mean of 3167 kg ha?1 and variation of 22.7%, while application of maize residue at 5 t ha?1 + 100% NPK gave a yield of 593 to 4591 kg ha?1 with a mean of 2518 kg ha?1 and variation of 39.3% over years. In FYM block, FYM at 10 t ha?1 + 100% NPK gave a significantly higher organic carbon (0.45%), available N (204 kg ha?1), available P (68.6 kg ha?1), and available K (107 kg ha?1) over years. In maize residue block, application of MR at 5 t ha?1 + 100% NPK gave a significantly higher organic carbon (0.39%), available soil N (190 kg ha?1), available soil P (47.5 kg ha?1), and available soil K (86 kg ha?1). The regression model (1) of yield as a function of seasonal rainfall, organic carbon, and soil P and K nutrients gave a predictability in the range of 0.19 under FYM at 10 t ha?1 to 0.51 under 100% NPK in FYM block compared to 0.30 under 100% NPK to 0.67 under MR at 5 t ha?1 application in MR block. The regression model (2) of yield as a function of seasonal rainfall, soil N, P, and K nutrients gave a predictability in the range of 0.11 under FYM at 10 t ha?1 to 0.52 under 100% NPK in FYM block compared to 0.18 under MR at 5 t ha?1 + 50% NPK to 0.60 under MR at 5 t ha?1 application in MR block. An assessment of yield sustainability under different crop seasonal rainfall situations indicated that FYM at 10 t ha?1 + 100% NPK was efficient in FYM block with a maximum Sustainability Yield Index (SYI) of 41.4% in <500 mm, 64.7% in 500–750 mm, 60.2% in 750–1000 mm and 60.4% in 1000–1250 mm rainfall, while MR at 5 t ha?1 + 100% NPK was efficient with SYI of 29.6% in <500 mm, 50.2% in 500–750 mm, 40.6% in 750–1000 mm, and 39.7% in 1000–1250 mm rainfall in semi-arid Alfisols. Thus, the results obtained from these long term studies incurring huge expenditure provide very good conjunctive nutrient use options with good conformity for different rainfall situations of rainfed semiarid tropical Alfisol soils for ensuring higher finger millet yield, maintaining higher SYI, and maintaining improved soil fertility.  相似文献   

8.
ABSTRACT

Phosphorus (P) nutrition of the rice-wheat (RW) systems of the Indo-Gangetic Plain of South Asia has become important due to the alternate flooding and drying cycles of this crop rotation. Field experiments on the RW cropping sequence were conducted at three locations of Bangladesh on three soil types. Two fertilizer doses—farmers' practice (FP) and soil-test based (STB), containing recommended amounts of P, nitrogen (N), potassium (K), and other nutrients—were compared with mungbean or maize as a third crop. The objective of the experiments was to detect P deficiency, if any, in rice, wheat, mungbean, and maize, and to compare the FP and STB doses of fertilizers in rice-wheat-mungbean and rice-wheat-maize sequences under two mungbean management practices (residue removed or retained) and one maize management practice (residue removed) in terms of P nutrition of those crops and annual system-level P removal and apparent P balance in the soil. The apparent P balance was negative with the FP dose (?1 to ?9 kg ha?1 for mungbean sequences at Joydebpur and Nashipur) and there was soil P accumulation under both the STB dose (9–49 kg ha?1) and zero N control (13–50 kg ha?1) across sites. The effect of maize or mungbean as the pre-rice crop on the apparent P balance of various RW sequences was not significant. Phosphorus deficiency occurred at all sites in wheat and maize, and at Ishwordi in rice, suggesting that P fertilizer recommendations need to be revised for RW systems in Bangladesh. The results also suggest that long-term monitoring for P concentration, uptake, and balance would be necessary for improving not only the productivity and sustainability of this system but also the fertilizer P-use efficiency.  相似文献   

9.
Rice is a major cereal crop in Himachal Pradesh, a Himalayan state of India, where paddy acreage is about 78,000 ha with a low average yield of 19.62 q ha?1 due to rainfed upland farming. High seeding rates and poor resource-use efficiency of conventional fertilizer nitrogen (N) management practices in rainfed upland paddy have also been major production constraints in rainfed upland ecosystems. To validate and refine the production technology on seed rate and fertilizer N management, the Farm Science Centre, Sundernagar, India, conducted numerous on-farm trials (OFTs) during 2006–2010 under an on-farm participatory technology development approach to enhance resource use efficiency through these resource conservation technologies and boost the paddy productivity in the region. Results of two OFTs conducted during Kharif 2006 in the Mandi District of Himachal Pradesh on different seed rates under different sowing methods on VL Dhan-221 and Sukaradhan-1 (HPR-1156) cultivars suitable for rainfed upland conditions revealed that the seed rate at 80 kg ha?1 sown in rows 20 cm apart resulted in the greatest average paddy productivity to the tune of 25.6 q ha?1 besides greater profitability, followed by a seed rate at 60 kg ha?1 sown in rows 20 cm apart (25.2 q ha?1), over the earlier State Agricultural University (SAU)–recommended practice, that is, seed rate at 100 kg ha?1 in rows 20 cm apart. This refinement in the seed rate was accepted by the participating farmers of the region. The greatest average benefit/cost (B/C) ratio was observed in plots with seed rate at 60 kg ha?1 sown in rows 20 cm apart. Based on these results and data compilation from other locations of the state, now the SAU has refined the seed rate from earlier recommendation of 100 kg ha?1 to 60 kg ha?1 in rows 20 cm apart as well as 80 kg ha?1 through broadcast method under rainfed upland paddy in Himachal Pradesh. Results of two OFTs conducted during Kharif 2009 on integrated nutrient management in rainfed upland paddy revealed that farmyard manure (FYM) at 10 t ha?1 + nitrogen, phosphorus, and potassium (N, P, K) at 15:30:30 kg ha?1 at sowing followed by 15 kg N ha?1 15 days after sowing (DAS) and remaining the N [i.e., 30 kg N ha?1] at tillering (45–50 DAS) resulted in the greatest grain yield of 29.85 and 31.67 q ha?1 in VL Dhan-221 and HPR-1156, respectively, with respective greater yields of 35.99 and 36.51% over farmers’ practice, besides better profitability. To further standardize fertilizer N split doses and assess their effect on paddy productivity, another OFT was conducted during Kharif 2010 under rainfed upland paddy conditions in HPR-1156. The results revealed that NPK at 60:30:30 kg ha?1 (whole of P and K as basal, 50% N at 15 DAS, 25% N each at 45–50 DAS and 70–75 DAS splits) resulted in better grain yield (34.3 q ha?1) and net profitability (?29,786 ha?1) over other treatments. Overall, it is concluded that these resource conservation technologies developed under the OFT participatory approach can enhance the rainfed upland paddy productivity and strongly show that there is dire need to split the N requirement of rainfed upland paddy in 2–3 splits to reduce the fertilizer N losses, enhance resource-use efficiency, and increase productivity and profitability in Himachal Pradesh, India.  相似文献   

10.
A laboratory study was conducted at the Indian Agricultural Research Institute, New Delhi on a sandy clay loam soil of pH 7.9 and organic C content of 0.34% to study the effect of incorporating Sesbania or Vigna legume residues or wheat straw at 15 and 30t ha?1 on temporal variation in ammoniacal and nitrate‐N in soil under submergence and well drained conditions. Under submergence most mineral N was present as ammoniacal‐N, while under well drained conditions it was present as Nitrate‐N. The content of ammoniacal N in soil was the highest after 30 days of incubation and declined thereafter under submergence. On the other hand under well drained conditions the mineral‐N (mostly nitrate) content in soil at 30 DAI was very little and showed increases only later, reaching the highest level at 90 DAI. Application of wheat straw specially at 301 ha?1 level resulted in immobilization of native soil‐N. These results show that rice which is grown under submergence can be transplanted soon after incorporation of legume residues, but for wheat or other crops which are grown under well drained condition a time interval of 30 days or more needs to be provided before sowing the crop.  相似文献   

11.
Abstract

Use of adequate rates of phosphorus (P) in crop production on high‐P‐fixing acid soils is essential because of high crop response to P fertilization and the high cost of P fertilizers. Information on lowland rice response to thermophosphate fertilization grown on Inceptisols is limited, and data are also lacking for soil‐test‐based P fertilization recommendations for this crop. The objective of this study was to evaluate response of lowland rice to added thermophosphate and to calibrate P soil testing for making P fertilizer recommendations. A field experiment was conducted for two consecutive years in central Brazil on a Haplaquept Inceptisol. The broadcast P rates used were 0, 131, 262, 393, 524, and 655 kg P ha?1, applied as thermophosphate Yoorin. Rice yield and yield components were significantly increased with the application of P fertilizer. Average maximum grain yield was obtained with the application of 509 kg P ha?1. Uptake of macro‐ and micronutrients had significant quadratic responses with increasing P rates. Application of thermophosphate significantly decreased soil acidity and created favorable macro‐ and micronutrient environment for lowland rice growth. Across 2 years, soil‐test levels of Mehlich 1–extractable P were categorized, based on relative grain yield, as very low (0–17 mg P kg?1 soil), low (17–32 mg P kg?1 soil), medium (32–45 mg P kg?1 soil), or high (>45 mg P kg?1 soil). Similarly, soil‐test levels of Bray 1–extractable P across 2 years were very low (0–17 mg P kg?1 soil), low (17–28 mg P kg?1 soil), medium (28–35 mg P kg?1 soil), or high (>35 mg P kg?1 soil). Soil P availability indices for Mehlich 1 extractant were slightly higher at higher P rates. However, both the extracting solutions had highly significant association with grain yield.  相似文献   

12.
ABSTRACT

Nitrogen (N) nutrition of the rice-wheat (RW) systems of the Indo-Gangetic Plain is important for sustaining the region's productivity and food needs. Soil N plays an important role in regulating the supply of N to plants. Monitoring plant concentrations, uptake, and balance of N assist in our understanding of plant and soil N status and in devising N-fertilizer strategies for both individual crops and a cropping system. Field experiments with rice-wheat-mungbean and rice-wheat-maize annual cropping sequences were conducted at Joydebpur, Nashipur, and Ishwordi in Bangladesh, which differ in their soils and climates. The experiments compared three pre-rice treatments (mungbean residues retained, mungbean residues removed, and maize residues removed), supplying each with two fertilizer levels (soil-test based, or STB, and farmers' practice, or FP). Zero N (control) treatments were included, with all other nutrients applied as STB or FP. The objectives were to detect N deficiency, if any, in the component crops, and to determine the changes in soil N fertility, plant N uptake, and soil N balance for various RW sequences. There was a significant decrease in mineral N in the topsoil (0–15 cm) of the +N mungbean and maize-residues removed treatments at Ishwordi, and a generally significant but less marked decline under the same treatments at Nashipur. Wheat and maize crops suffered from N deficiency ranging from 33% to 95% each year, at all sites, but deficiency in rice and mungbean was minimal. Annual system-level N uptake across sites ranged from 89 kg ha?1 for the control to 239 kg ha?1 for sequences containing maize with N. There were significant linear relationships between total system productivity (TSP) and annual N application and between TSP and annual system-level N uptake. Considering no N loss through the system, N fertilizer resulted in a positive N balance that ranged between 24–190 kg ha?1 compared with a negative balance of between 40–49 kg ha?1 without it. However, if a 30% N loss was assumed, N balances were reduced to between ?37–62 kg/ha?1 for N-containing treatments, and to between ?64–55 kg/ha?1 for the control treatments. Further research is needed to understand N depletion and replenishment and to sustain the productivity of the RW system.  相似文献   

13.
Based on experiments conducted during 1988–2009 on rainfed pearl millet/sorghum with 9 treatments in Vertisols, an efficient treatment for sustainable productivity is identified. Twenty kg of nitrogen (N) from farmyard manure (FYM) + 20 kg N (urea) + 10 kg phosphorus (P) ha?1 in pearl millet and 40 kg N (urea) + 20 kg P + 25 kg zinc sulfate (ZnSO4) ha?1 in sorghum gave maximum yield and rainwater-use efficiency, whereas 20 kg N (FYM) + 20 kg (urea) + 10 kg P ha?1 in pearl millet and 40 kg (urea) + 20 kg P ha?1 in sorghum and gave maximum soil N, P, and potassium (K) over years. The regression model of 20 kg N (crop residue) + 20 kg N (urea) + 10 kg P ha?1 gave maximum R2 for predicting sorghum equivalent yield separately through precipitation and soil variables, whereas 20 kg N (FYM) + 20 kg N (urea) + 10 kg P ha?1 gave maximum R2 under combined model of both variables. Treatment of 20 kg N (FYM) + 20 kg N (urea) + 10 kg P ha?1 was superior for attaining maximum sorghum equivalent yield of 1062 kg ha?1, net returns of Rs. 4805 ha?1, benefit/cost (BC) ratio of 1.50, and 127 kg ha?1 of soil N, 10.3 kg ha?1 of soil P, and 386 kg ha?1 of soil K over years.  相似文献   

14.
Different methods of fertilizer application-drip fertigation and conventional fertilizer application under drip, surface irrigation, and rainfed conditions were evaluated during 2009–2012 at Krishi Vigyan Kendra, Shimla, India. The experiment was arranged in randomized block design (RBD), replicated thrice. Results suggest that fertigation significantly increased growth parameters over conventional methods. Fruit yield was significantly higher under fertigation (13.7 t ha?1) over conventional fertilizer application with drip (11.6 t ha?1), surface irrigation (10.6 t ha?1), and under rainfed (8.6 t ha?1). Fruit quality parameters were also superior under fertigation. Fertigation maintained higher available nitrogen (N) and potassium (K) content in 0-30 cm soil layers. Available phosphorus (P) was higher in 0-20 cm soil depths in all the treatments. Fertigation with 80 and 100 percent recommended NPK dose registered statistically comparable results. In addition to higher productivity, fertigation resulted in 20 percent fertilizer savings over drip irrigation and 20 percent fertilizer besides 40 percent water savings over surface irrigation.  相似文献   

15.
Abstract

Quantitative assessment of soil nitrogen (N) that will become available is important for determining fertilizer needs of crops. Nitrogen‐supplying capacity of soil to rice and wheat was quantified by establishing zero‐N plots at on‐farm locations to which all nutrients except N were adequately supplied. Nitrogen uptake in zero‐N plots ranged from 41.4 to 110.3 kg N ha?1 for rice and 33.7 to 123.4 kg N ha?1 for wheat. Availability of soil N was also studied using oxidative, hydrolytic, and autoclaving indices, salt‐extraction indices, light‐absorption indices, and aerobic and anaerobic incubation indices. These were correlated with yield and N uptake by rice and wheat in zero‐N plots. Nitrogen extracted by alkaline KMnO4 and phosphate borate buffer and nitrogen mineralized under aerobic incubation were satisfactory indices of soil N supply. For rice, 2 M KCl and alkaline KMnO4 were the best N‐availability indices. Thus, alkaline KMnO4 should prove a quick and reliable indicator of indigenous soil N supply in soils under a rice–wheat cropping system.  相似文献   

16.
Studies were conducted on paddy soils to ascertain N2 fixation, growth, and N supplying ability of some green-manure crops and grain legumes. In a 60-day pot trial, sunhemp (Crotalaria juncia) produced a significantly higher dry matter content and N yield than Sesbania sesban, S. rostrata, cowpeas (Vigna unguiculata), and blackgram (V. mungo), deriving 91% of its N content from the atmosphere. Dry matter production and N yield by the legumes were significantly correlated with the quantity of N2 fixed. In a lowland field study involving sunhemp, blackgram, cowpeas, and mungbean, the former produced the highest stover yield and the stover N content, accumulating 160–250 kg N ha-1 in 60 days, and showed great promise as a biofertilizer for rice. The grain legumes showed good adaptability to rice-based cropping systems and produced a seed yield of 1125–2080 kg ha-1, depending on the location, species, and cultivar. Significant inter- and intraspecific differences in the stover N content were evident among the grain legumes, with blackgram having the highest N (104–155 kg N ha-1). In a trial on sequential cropping, the groundnut (Arachis hypogaea) showed a significantly higher N2 fixation and residual N effect on the succeeding rice crop than cowpeas, blackgram, mungbeans (V. radiata), and pigeonpeas (Cajanus cajan). The growth and N yield of the rice crop were positively correlated with the quantity of N2 fixed by the preceding legume crop.  相似文献   

17.
Intensive rice-based cropping systems rely on nitrogenous fertilizer for optimum grain production and legume crops could be used as an alternative nitrogen (N) source for rice. We investigated the fate of N applied to dual cropping wetland rice in the form of legume residue and 15N labeled fertilizer. In 2001–2002, hairy vetch and broad bean accumulated 131 and 352 kg N ha?1 of which 41 and 78% was derived from N2 fixation. In 2002–2003, hairy vetch accumulated 64 kg N ha?1 and broad bean accumulated 320 kg N ha?1 of which 21 to 24% was derived from hairy vetch and 31 to 82% N was derived from broad bean by N difference and 15N-natural abundance method. Our results reveal that hairy vetch and broad bean can supply 50–100% of N required for intensive wetland rice and can be a viable alternative N source to enhance soil fertility.  相似文献   

18.
The relatively low solubility and availability of phosphorus (P) from indigenous phosphate rock could be enhanced by legumes in the acid soils of humid forest agroecosystems. Crotalaria micans L. was grown in a screenhouse without P or with P from triple superphosphate (TSP) and Malian Tilemsi Rock P. The P response of 20 cover crops was field‐evaluated using TSP and Rock P. In both experiments, the fertilized cover crops were followed by upland rice without mineral N or P application. Mean rice grain yield and agronomic residual P‐use efficiency were similar for both P sources. In the field, 1‐year fallow treatment of Canavalia ensiformis (velvet bean) supplied with Mali Rock P gave the highest rice grain yield of 3.1 Mg ha?1, more than 180% that of 2‐year continuous unfertilized rice (cv. ‘WAB 56‐50’). Among continuous rice plots, ‘NERICA 2’ (interspecific rice) supplied with Rock P produced the highest yield (2.0 Mg ha?1), suggesting that ‘NERICA 2’ might have greater potential to solubilize rock P. Results indicate that when combined with an appropriate legume, indigenous rock‐P can release sufficient P to meet the P requirement of the legume and a following upland rice crop in rotation.  相似文献   

19.
Approximately 40% of New Zealand's land mass is fertilized grassland with entirely non‐native plants, but currently there is substantially increased interest in restoration of native plants into contemporary agricultural matrices. Native vegetation is adapted to more acid and less fertile soils and their establishment and growth may be constrained by nutrient spillover from agricultural land. We investigated plant–soil interactions of native N‐fixing and early successional non N‐fixing plants in soils with variable fertility. The effects of soil amendments of urea (100 and 300 kg N ha?1), lime (6000 kg CaCO3 ha?1), and superphosphate (470 kg ha?1) and combinations of these treatments were evaluated in a glasshouse pot trial. Plant growth, soil pH, soil mineral N, Olsen P and nodule nitrogenase activity in N‐fixing plants were measured. Urea amendments to soil were not inhibitory to the growth of native N‐fixing plants at lower N application rates; two species responded positively to combinations of N, P and lime. Phosphate enrichment enhanced nodulation in N‐fixers, but nitrogen inhibited nodulation, reduced soil pH and provided higher nitrate concentrations in soil. The contribution of mineral N to soil from the 1‐year old N‐fixing plants was small, in amounts extrapolated to be 10–14 kg ha?1 y?1. Urea, applied both alone and in conjunction with other amendments, enhanced the growth of the non N‐fixing species, which exploited mineral N more efficiently; without N, application of lime and P had little effect or was detrimental. The results showed native N‐fixing plants can be embedded in agroecology systems without significant risk of further increasing soil fertility or enhancing nitrate leaching.  相似文献   

20.
Abstract

Yield and kernel quality of rainfed maize as affected by N fertilizer has been generally evaluated through the application of granular N sources at high rates. The purpose of this work was to estimate the response of maize yield and quality (kernel hardness—floating index, weight and test weight -, P uptake and protein) to foliar N application and preceding granular N. Data for this report were collected in 2014 and 2015 in a long-term experiment established in 2002 under permanent beds in a split plot arrangement. Main plot treatments were three foliar N rates (0, 4.5 and 9?kg ha?1) laid out on the top of four preceding granular N rates (0, 20, 40 and 60?kg ha?1) applied from 2002 to 2013 as subplots. Weather conditions were relatively wetter in 2014 than 2015. In 2014, test weight and floating index improved over that in 2015. Foliar application of 9?kg N ha?1 enhanced yield and protein. In 2014, yield response to preceding N rates showed an increasing trend whereas in 2015 response was null. Kernel P uptake response to preceding N rates showed a differential reaction among foliar N rates; 9?kg ha?1 showed the greatest uptake. Kernel floating index was associated to kernel P uptake. Apparently, this relationship has not been previously reported. Results suggests that the application of 9?kg N ha?1 to foliage of rainfed maize grown in permanent beds has the potential to substitute the traditional fertilization practice of granular N sources.  相似文献   

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