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1.
Chickpea (Cicer arietinum L.), a large seeded pulse legume, is nodulated only by a very specific group of Rhizobium strains which do not nodulate plants other than Cicer spp. If the cotyledons are removed just after germination, subsequent seedling growth is dwarfed, and plants will reliably grow and nodulate in large test tubes (25 × 200 mm) under axenic conditions with either sand or sand + venniculite as the root medium. The dwarfed seedlings of some selected chickpea lines can be used as a “trap host” for counting Cicer-Rhizobium in pure cultures and contaminated materials by a most probable number, serial dilution-plant infection technique. The value of such a plantlet as a “trap host” for studying Cicer-Rhizobium ecology, strain authentication and inoculum quality control is demonstrated.  相似文献   
2.
Legumes grown for grain may or may not contribute net N benefits to soil and succeeding crops. An experiment was conducted to assess N2 fixation attributes of six mungbean cultivars and two groundnut cultivars (Tainan 9 and Non-nod), which determine their residual benefit to the subsequent maize. Nodule number and dry weight of mungbeans peaked early (at 45 days) and declined thereafter strongly. In groundnut nodulation peaked later and declined only by 50% towards the final harvest. The N2-fixing groundnut produced higher total dry matter yield than mungbeans; however, mungbeans produced higher seed yields. Dry matter harvest index and nitrogen harvest index (NHI) were higher in mungbeans (average 0.44 and 0.69) than groundnut (0.23 and 0.47, respectively, in Tainan 9). The percentage of nitrogen derived from air (%Ndfa, 15N isotope dilution) ranged from 54% to 62% in mungbeans, similar to that of groundnut (64%). However, Tainan 9 fixed more N2 (82 kg N ha–1) than mungbeans (35–50 kg N ha–1) and resulted in a positive soil net N balance (+22 kg N ha–1) while negative values were found for Non-nod groundnut and mungbeans (–3 to –12 kg N ha–1). Maize grown after groundnut Tainan 9 had the highest total dry weight and total N uptake. This was equivalent to maize grown in fallow plots, which received 60–90 kg N ha–1, while the respective benefits after mungbeans were 30–60 kg N ha–1. Maize yield was directly related to the amount of residue N returned. Thus, the combination of high N yield, residue quality, %Ndfa and low NHI proved most beneficial to soil fertility and the succeeding crop.  相似文献   
3.
Burning of sugarcane residues contributes to air pollution and sugarcane producers have been forced to abandon it. The change from burning to residue retention is likely to alter the cycling of nutrients. Additionally, there is often a time gap of 6–8 months between two different sugarcane cycles during which legumes could be planted. Thus, the objective of this study was to assess the effects of burning, mulching or incorporation of sugarcane residues on residue decomposition and N mineralization (sugarcane residue management period) and subsequently upon ploughing (legume period) on N dynamics, N2 fixation, development and nutrient yields of groundnut and soybean grown between two sugarcane cycles on a sandy soil in Northeast Thailand.

Soil microbial biomass N increased when sugarcane residues were incorporated instead of burned or surface applied at 14 days after initiation of cane residue management. Thereafter, high net N mineralization was accompanied by a reduction in microbial biomass N, indicating that mineralized N was derived from microbial N turnover. However, upon ploughing after 96 days the different previous sugarcane residue management strategies had no significant (P > 0.05) effect on net mineral N and microbial biomass N during the subsequent legume period. Although, 15N enrichment in control reference plants and plant N uptake indicated significant N immobilization effects persisting into the legume crop phase, the proportion of N derived from N2 fixation (%Ndfa) or amount of N2 fixed were not significantly different between sugarcane residue management treatments. Soybean fixed more N2 (78%Ndfa, 234 kg N fixed ha−1) than groundnut (67%Ndfa, 170 kg N fixed ha−1) due to its larger N demand and a poorer utilization of soil N (64 kg N ha−1 vs. 85 kg N ha−1). Groundnut led to a positive soil N balance while that of soybean was negative due to its high nitrogen harvest index. Legume residues returned 61 and 146 kg N ha−1 to the soil for soybean and groundnut, respectively, compared to only 34–39 kg N ha−1 by fallow weeds. Sugarcane residue retention improved soil organic carbon and N content. The results suggested that although a change from burning to sugarcane residues retention led to alterations in N cycling and improved soil organic matter it did not significantly affect N2 fixation due to the uniforming action of ploughing and the extended time gap between sugarcane residue incorporation and legume planting.  相似文献   

4.
Drought during the pre‐flowering stage can increase yield of peanut. There is limited information on genotypic variation for tolerance to and recovery from pre‐flowering drought (PFD) and more importantly the physiological traits underlying genotypic variation. The objectives of this study were to determine the effects of moisture stress during the pre‐flowering phase on pod yield and to understand some of the physiological responses underlying genotypic variation in response to and recovery from PFD. A glasshouse and field experiments were conducted at Khon Kaen University, Thailand. The glasshouse experiment was a randomized complete block design consisting of two watering regimes, i.e. fully‐irrigated control and 1/3 available soil water from emergence to 40 days after emergence followed by adequate water supply, and 12 peanut genotypes. The field experiment was a split‐plot design with two watering regimes as main‐plots, and 12 peanut genotypes as sub‐plots. Measurements of N2 fixation, leaf area (LA) were made in both experiments. In addition, root growth was measured in the glasshouse experiment. Imposition of PFD followed by recovery resulted in an average increase in yield of 24 % (range from 10 % to 57 %) and 12 % (range from 2 % to 51 %) in the field and glasshouse experiments, respectively. Significant genotypic variation for N2 fixation, LA and root growth was also observed after recovery. The study revealed that recovery growth following release of PFD had a stronger influence on final yield than tolerance to water deficits during the PFD. A combination of N2 fixation, LA and root growth accounted for a major portion of the genotypic variation in yield (r = 0.68–0.93) suggesting that these traits could be used as selection criteria for identifying genotypes with rapid recovery from PFD. A combined analysis of glasshouse and field experiments showed that LA and N2 fixation during the recovery had low genotype × environment interaction indicating potential for using these traits for selecting genotypes in peanut improvement programs.  相似文献   
5.
This research studied the effect of biochar addition before upland rice planting, followed by sugarcane cropping, on soil fertility (nitrogen mineralization, β-glucosidase and urease activities), and mitigating greenhouse gases emission at sugarcane harvest. An incubation experiment was designed utilizing soil samples taken from a sugarcane field at final harvest with treatments, (i) Control, with no biochar or fertilizer application to upland rice (ii) CF, with fertilizer application at recommended rates; (iii) BC1, with biochar addition at the rate of 3.125?Mg ha?1 + CF; (iv) BC2, with biochar addition at the rate of 6.25?Mg ha?1 + CF. Results showed that, at the last sampling dates, soil enzyme activities of the biochar treatments were significantly greater than those of the control treatment. The lowest cumulative carbon dioxide and nitrous oxide emission was observed in the BC2 treatment. Thus, the BC2 treatment could increase both soil fertility and mitigate global warming.  相似文献   
6.
Groundnut as a pre-rice crop is usually harvested 1–2 months before rice transplanting. During this lag phase much of N in groundnut residues could be lost due to rapid N mineralization. Mixing of abundantly available rice straw with groundnut residues may be a means for reducing N and improve subsequent crop yields. The objectives of this experiment were to investigate the effect of mixing groundnut residues and rice straw in different proportions on (a) growth and yield of succeeding rice, (b) groundnut residue N use efficiency and (c) N lost (15N balance) from the plant–soil system and fate of residue N in soil fractions. The experiment consisted of six treatments: (i) control (no residues), (ii) NPK (at recommended rate, 38 kg N ha−1), (iii) groundnut residues 5 Mg ha−1 (120 kg N ha−1), (iv) rice straw 5 Mg ha−1 (25 kg N ha−1), (v) 1:0.5 mixed (groundnut residues 5 Mg: rice straw 2.5 Mg ha−1), and (vi) 1:1 mixed (groundnut residues 5 Mg: rice straw 5 Mg ha−1). After rice transplanting, samples of the lowland rice cultivar KDML 105 were periodically collected to determine growth and nutrient uptake. At final harvest, dry weight, nutrient contents and 15N recovery of labeled groundnut residues were evaluated.  相似文献   
7.
In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.  相似文献   
8.
The relationship between biomass production and N2 fixation under drought‐stress conditions in peanut genotypes with different levels of drought resistance is not well understood. The objective of this study was to determine the effect of drought on biomass production and N2 fixation by evaluating the relative values of these two traits under well watered and water‐stress conditions. Twelve peanut genotypes were tested under field conditions in the dry seasons of 2003/2004 and 2004/2005 in north‐east Thailand. A split‐plot design with four replications was used. Main‐plot treatments were three water regimes [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW], and sub‐plot treatments were 12 peanut lines. Data were recorded on biomass production and N2 fixation under well watered and water‐stress conditions. Genotypic variations in biomass production and N2 fixation were found at all water regimes. Biomass production and N2 fixation decreased with increasing levels of drought stress. Genotypes did not significantly differ in reductions for biomass production, but did differ for reductions in N2 fixation. High biomass production under both mild and severe drought‐stress conditions was due largely to high potential biomass production under well‐watered conditions and, to a lesser extent, the ability to maintain high biomass production under drought‐stress conditions. High N2 fixation under drought stress also was due largely to high N2 fixation under well‐watered conditions with significant but lower contributions from the ability to maintain high nitrogen fixation under drought stress. N2 fixation at FC was not correlated with the reduction in N2 fixation at 2/3 AW and 1/3 AW. Positive relationships between N2 fixed and biomass production of the tested peanut genotypes were found at both levels of drought stress, and the relationship was stronger the more severe the drought stress. These results suggested that the ability to maintain high N2 fixation under drought stress could aid peanut genotypes in maintaining high yield under water‐limited conditions.  相似文献   
9.
Groundnut as a pre‐rice crop is usually harvested 1–2 months before rice transplanting, during which much of legume residue N released could be lost. Our objectives were to investigate the effect of mixing groundnut residues (GN, 5 Mg ha?1) with rice straw (RS) in different proportions on: (i) regulating N dynamics, (ii) potential microbial interactions during decomposition, and (iii) associated nitrous oxide and methane emissions at weekly intervals during the lag phase until rice transplanting (i, ii) or harvest (iii). Decomposition was fastest in groundnut residues (64% N lost) with a negative interaction for N loss when mixed 1:1 with rice straw. Adding groundnut residues increased mineral N initially, while added rice straw led to initial microbial N immobilization. Mineral N in mixed residue treatments was significantly greatest at the beginning of rice transplanting. Soil microbial N and apparent efficiency were higher, while absolute and relative microbial C were often lowest in groundnut and mixed treatments. Microbial C:N ratio increased with increasing proportion of added rice straw. N2O losses were largest in the groundnut treatment (12.2 mg N2O‐N m?2 day?1) in the first week after residue incorporation and reduced by adding rice straw. N2O‐N emissions till rice harvest amounted to 0.73 g N2O‐N m?2 in the groundnut treatment. CH4 emissions were largest in mixed treatments (e.g. 155.9 g CH4 m?2, 1:1 treatment). Mixing residues resulted in a significant interaction in that observed gaseous losses were greater than predicted from a purely additive effect. It appears possible to regulate N dynamics by mixing rice straw with groundnut residues; however, at a trade‐off of increased CH4 emissions.  相似文献   
10.
Water stress during the vegetative development normally is not detrimental and sometimes actually increases yield of peanut (Arachis hypogaea L.). Root growth might play an important role in response to early season drought in peanut and might result in an increase in yield. Information on the response of root characters of diverse peanut genotypes to these conditions will provide useful information for explaining mechanisms and improving peanut genotypes for exploiting positive interaction for pod yield under pre-flowering drought. The aim of this study, therefore, was to investigate the root dry weight and root length density of peanut genotypes with different yield responses to pre-flowering drought stress and their relationships with pod yield. Field experiments were conducted at the Field Crop Research Station of Khon Kaen University, Khon Kaen, Thailand during February to July 2007 and during February to July 2009. A split-plot experiment in a randomized complete block design was used. Two water management treatments were assigned as the main plots, i.e. field capacity and pre-flowering stress, and six peanut genotypes as the sub-plots. Total crop dry matter, root dry weight and root length density were recorded at 25 DAE, R5 and R7. Top dry weight and pod yield were measured at harvest and pod harvest index (PHI) was computed using the data on pod yield and biomass. Peanut genotypes were categorized into three groups based on their responses to drought for pod yield, e.g. increasing, decreasing and non-responsive groups. The genotypes of each group showed a differential response for root quantity and distribution. The increasing pod yield group had more root dry weight and root length density in the deeper soil layers during pre-flowering stress compared to the non-stress treatment. The non-responsive group showed no root response under pre-flowering drought conditions compared to the non-stress treatment. A larger root system alone without considering distribution may not contribute much to pod yield but a higher RLD at deeper layers may allow plants to mine more available water in the sub-soil. However, as yield is a complex trait, several mechanisms may be involved. The increasing pod yield group also had the ability to maintain a high PHI.  相似文献   
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