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The ability of adaptation of Rhizobia in diverse environment namely, soil, rhizosphere and grown within legume roots may lead to nitrogen fixation, in a complicated process which contain a coordinated exchange of signal between plants and the symbionts. Green manures, cash and cover crops have significant role in soil fertility. Green manuring techniques also can decrease biomass burning known as main source of air pollutant in the atmosphere. Catch crops have positive effects on both physical and chemical properties of soil, subsequent crop yield, decrease nitrogen leaching into the ground water, decrease soil erosion, and decrease nitrogen losses in cropping systems. Cover crops are those crops which cover the ground and protect loss of plant nutrients, the soil from erosion, decrease rate of soil moisture by evaporation, lower ground temperature and improve weed control and nutrient recycling. Rhizobia produce Nod factors during the early development of nodules upon perception of flavonoid molecules secreted by legume roots, and Nod factor's structure dependents on species, chemical, substitutions added which may influence legume specificity. The benefic effects of rhizobia may depend on rhizobium strain, the genotype of the legume, management practices and bio-physical environment. Rhizobium can directly promote both plant growth and plant health, and modulating root architecture and growth via the release of plant phytohormones. In this manuscript, we want to review the most important advantages and benefits of green manures, catch and cover crops with considering the positive effects of rhizobium on soil fertility and sustainable agricultural production. [ABSTRACT FROM AUTHOR]

Legumes are used in crop rotations by both large‐scale and smallholder farmers alike to increase soil fertility, especially before high‐nitrogen‐demanding crops such as corn (maize). Legume crop residues and green manures are rich in nitrogen due to mutualistic rhizobia, bacteria that live in their roots and convert atmospheric nitrogen into a biologically available form. Growers can obtain recommendations from local extension offices about how much less inorganic nitrogen fertilizer needs to be added to a subsequent crop following different legume break crops for the predominant soil type (the nitrogen fertilizer replacement value, or NFRV). Due to the intimate relationship between legumes and rhizobia, conditions that affect plant health can also affect the rhizobia and how much nitrogen they provide. We use a combination of empirical data and previously published values to estimate reductions in nitrogen inputs under outbreaks of plant viruses of varying severity. We also use historical fertilizer prices to examine the economic impacts of this lost fertilizer for farmers. We find that fertilizer losses are greatest for crops that fix large amounts of nitrogen, such as clover and alfalfa as opposed to common bean. The economic impact on farmers is controlled by the proportion of plants with viral infections and the price of synthetic fertilizer. In a year of high disease prevalence, attention is normally focused on the yield of the diseased crops. We suggest that farmers growing legumes as break crops should be concerned about yields of subsequent crops as well. Viral diseases can be difficult to diagnose in the field, so the easiest way for farmers to prevent unexpected yield losses in subsequent crops is to test their soil when it is feasible to do so. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the effects of cowpea green manure and inorganic nitrogen (N) fertilizers on yields of winter wheat and soil emissions of nitrous oxide (N2O). The comparisons included cowpea grown solely as green manure where all biomass was terminated at maturity by tillage, summer fallow treatments with 90 kg N ha−1 as urea (90-N), and no fertilization (control) at planting of winter wheat. Fluxes of N2O were measured by closed chamber methods after soil incorporation of cowpea in autumn (October–November) and harvesting of winter wheat in summer (June–August). Growth and yields of winter wheat and N concentrations in grain and straw were also measured. Cowpea produced 9.5 Mg ha−1 shoot biomass with 253 kg N ha−1 at termination. Although soil moisture was favorable for denitrification after soil incorporation of cowpea biomass, low concentrations of soil mineral N restricted emissions of N2O from cowpea treatment. However, increased concentrations of soil mineral N and large rainfall-induced emissions were recorded from the cowpea treatment during summer. Growth of winter wheat, yield, and grain N concentrations were lowest in response to cowpea treatment and highest in 90-N treatment. In conclusion, late terminated cowpea may reduce yield of winter wheat and increase emissions of N2O outside of wheat growing seasons due to poor synchronization of N mineralization from cowpea biomass with N-demand of winter wheat. [ABSTRACT FROM AUTHOR]

Background and aims: Crucifers grown as cover crops are known to reduce sulphate leaching (S catch-crop service) and release large amounts of mineral sulphate for the subsequent cash crop once incorporated into the soil (S green-manure service). Crucifer-legume cover crop mixtures are effective to obtain high nitrogen related services, but few data exist on their performances for S-related services. Our study aimed to assess performances of a wide variety of bispecific crucifer-legume mixtures designed to provide soil S catch-crop and S green-manure services.Methods: A two-year field experiment was conducted at two sites near Toulouse, France (silt clay loam soil) and Orléans, France (sandy loam soil) in which cultivars from eight crucifer species and nine legume species were tested as sole and bispecific cover crops.Results: Crucifer-legume mixtures and crucifer sole cover crops provided the same level of S catch-crop service (12 kg S ha−1), significantly higher than that of legume sole cover crops (4 kg S ha−1). Similarly, crucifer-legume mixtures provided almost the same level of S green-manure service (5.5 kg S ha−1) as crucifer sole cover crops (6.5 kg S ha−1).Conclusion: Our results demonstrate the compatibility and complementarity of certain crucifer and legume species when grown together to provide S and N catch-crop and green-manure services. For a same cover crop species no strong cultivar effect has been highlighted in our growing conditions. [ABSTRACT FROM AUTHOR]

Winter cover crops may provide different environmental benefits in agricultural systems. The aim of this study was to determine the effect of cover crops used as green manure on the soil nitrogen (N) budget and yield of silage maize (Zea mays L.). A field experiment was conducted between 2011 and 2013 at three locations in Vojvodina Province, Serbia. It compared common vetch (Vicia sativa L.), triticale (× Triticosecale Wittm. ex A. Camus), their mixture grown as cover crops, N fertilisation at two doses (N1 and N2), and an unfertilised fallow as a control. Cover crops were sown in autumn 2011 and 2012 and were ploughed in during May of the year after which silage maize was sown. Results show that the ability of cover crops to provide benefit for a subsequent crop is highly related to weather conditions, mainly precipitation. The two years of the study experienced completely different weather conditions, showing two aspects of how cover crops can affect subsequent crop yield and amount of N left in the soil. In 2012, the N budget was higher in all three cover crops at all locations than N1 and the control because of unfavourable weather conditions for mineralisation of organic matter. However, the cover crops had a negative effect on silage maize yield. In 2013 (an average year), the N budget was significantly higher after cover crops, and was followed by a higher yield of silage maize. Based on the 2-year average, the highest value of apparent N remaining in the soil was recorded in the mixture treatment (288.13 kg N ha-1); treatments with vetch and triticale had approximately equal values (272.17 and 272.71 kg N ha-1). The N fertilisation treatments and the control had significantly lower average values of residual N. [ABSTRACT FROM AUTHOR]

Cover crops constitute one of the most promising agronomic practices towards a more sustainable agriculture. Their beneficial effects on main crops, soil and environment are many and various, while risks and disadvantages may also appear. Several legumes show a high potential but further research is required in order to suggest the optimal legume cover crops for each case in terms of their productivity and ability to suppress weeds. The additional cost associated with cover crops should also be addressed and in this context the use of grain legumes such as cowpea, faba bean and pea could be of high interest. Some of the aspects of these grain legumes as far as their use as cover crops, their genetic diversity and their breeding using conventional and molecular approaches are discussed in the present review. The specific species seem to have a high potential for use as cover crops, especially if their noticeable genetic diversity is exploited and their breeding focuses on several desirable traits. [ABSTRACT FROM AUTHOR]