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Feeding a growing population and preventing dangerous climate change are two challenges facing humanity. Biological nitrogen (N) fixation is considered a sustainable production measure that helps maintain crop production and mitigate climate change by supplementing alternative N nutrients. However, the simultaneous impacts of symbiotic N fixation (SNF) by leguminous green manure crops on rice crop production and nitrous oxide (N 2 O) emissions remain poorly understood. Here, a field experiment of two annual rotation cycles was conducted to monitor rice yield and the N 2 O emissions under rice (Oryza sativa subsp. japonica Kato.)-wheat (Triticum aestivum L.) (RW) and rice-hairy vetch (Vicia villosa Roth.) (RV) cropping systems at three N input rates (0 (N0), 50 (N1) and 100 (N2) kg ha−1) for the upland crops and 200 kg ha−1 for the rice crop. Growing hairy vetch introduced a significant amount of N as SNF to the agroecosystem, ranging from 123 to 182 kg ha−1. Compared to the treatments without N for the RV system, the N1 and N2 treatments significantly increased the amount of SNF by 44–47% and 19%− 24%, respectively. The cumulative N 2 O emissions from SNF ranged from 0.28–0.65 kg ha−1, with the N 2 O emission factor from SNF (EF SNF) ranging from 0.18%− 0.52% for the RV system. The RV system significantly decreased the N 2 O emission factor from the total N input (EF TN) by an average of 10.0% compared with the RW system. The RV-N1 treatment produced an obviously lower EF TN , averaging 0.37%, than the other treatments receiving N applications. Compared to the RW system, the RV system slightly increased rice yield by an average of 3.5%. Therefore, the most appropriate N application rate was 50 kg ha−1 for the leguminous crop, and SNF of leguminous green manure could serve as complementary to mineral N fertilizers for reducing N 2 O emissions while improving soil quality and rice yield in paddy field. [Display omitted] • Symbiotic nitrogen fixation (SNF) contributed 58.1-84.9% of N uptake by hairy vetch. • N 2 O emission factor from SNF (0.18%−0.52%) was firstly established in agroecosystems. • The N1 at 50 kg ha−1 facilitated SNF and reduced N 2 O emission factor of total N input. [ABSTRACT FROM AUTHOR]

Green manure application in agricultural soil is known to enhance nitrogen use efficiency and crop yield. However, limited research exists on the potential effects of green manure returning on N 2 O emissions. This study aims to investigate the effects and underlying mechanisms of N 2 O emissions in maize fields under different green manure management practices. A field experiment was conducted using common vetch as a green manure crop following the harvest of spring wheat. The study employed a completely randomized block design and examined four treatments: tillage with total green manure incorporation, no-tillage with total green manure mulching (NTG), tillage with green manure root incorporation (T), and no-tillage with aboveground green manure removal (NT). The study explored both non-biological and biological factors affecting nitrogen conversion to elucidate the mechanisms in N 2 O emissions. N 2 O emissions were 17.7% lower in TG and NTG compared to T and NT (P < 0.01), with NTG showing a 12.2% reduction compared to TG (P < 0.05). NTG also exhibited the lowest average N 2 O fluxes at 24.2 μg N m−2 h−1. In terms of non-biological factors, N 2 O emissions were negatively correlated only with aggregate NH 4 +-N and NO 3 －-N (P < 0.05). Despite increasing soil mineral nitrogen, NTG had approximately 72.3%− 92.4% of it in the form of aggregate nitrogen. In addition, under NTG, the aggregates have better structure and stability. q-PCR analysis revealed higher nos Z gene abundance in NTG than in other treatments (P < 0.05). Regression analysis showed that N 2 O emissions were negatively correlated with nos Z's abundance and N 2 O reductase diversity (P < 0.05). No-tillage with total green manure mulching (NTG) effectively reduced N 2 O emissions by enhancing mineral nitrogen in soil aggregates and increasing the abundance of the nos Z gene. Our findings offer valuable insights for long-term agricultural management strategies aimed at improving nitrogen retention and mitigating climate change impacts. • No-till mulch with green manure retention reduces N 2 O emissions from maize fields. • N 2 O emissions are reduced by increasing aggregate mineral nitrogen in soil mineral nitrogen. • N 2 O emissions are also reduced by enhancing nos Z's abundance. [ABSTRACT FROM AUTHOR]

Increasing rice production to feed the world’s growing population while protecting the environment requires more optimal use of fertilizers. In China, the current high input, high output and high reliance on synthetic nitrogen (N) fertilizer in agriculture has resulted in high N losses, especially ammonia (NH 3 ) emission. Urea combined with green manure (GM) might be a promising approach to improve N fertilizer management. However, few studies have evaluated duckweed in this manner. Duckweed does not require arable land for cultivation and thus avoids competition with food crops. Therefore, a field experiment was conducted for three years with five treatments (CK, no N-fertilizer; CT, conventional practice, urea alone at 300 kg N ha −1 ; CTD, urea combined with duckweed at 300 kg N ha −1 ; RN, urea alone at 225 kg N ha −1 ; and RND, urea combined with duckweed at 225 kg N ha −1 ) in an intensive rice cropping system in the Taihu Region of China. The results for two years showed that urea combined with duckweed cover reduced NH 3 loss by 36–52% over CT. This reduction was attributed primarily to the formation of a physical barrier and the uptake of NH 4 + by duckweed. The 15 N recovery for 15 N balance conducted for one year was 38% higher and the 15 N loss was 16% lower for CTD than that of CT. Furthermore, urea combined with duckweed increased N accumulation in the aboveground plants by 14–25% over CT for the 3 years. As a result, urea combined with duckweed achieved higher rice yield by 9–10%, and higher net economic benefit by 10–11% over CT for the 3 years; however, using the conventional rate of 300 kg N ha −1 did not increase rice yield over using the reduced N rate of 225 kg N ha −1 , with or without duckweed. Thus, duckweed as GM combined with chemical fertilizer application provided an approach for increasing the rice yield without increasing inputs of N fertilizer and thereby provided a financially attractive option for farmers to achieve environmental integrity and ensure food security in rice production. [ABSTRACT FROM AUTHOR]

Biochar has been shown to reduce soil emissions of CO 2 , CH 4 and N 2 O in short-term incubation and greenhouse experiments. Such controlled experiments failed to represent variable field conditions, and rarely included crop growth feedback. The objective of this study was to assess the effect of biochar, in comparison to green manure and mineral nitrogen, on greenhouse gas Emissions Intensity (EI = emissions in CO 2 equivalents per ton of grain yield) in a low-fertility tropical Ultisol. Using a field trial in western Kenya, biochar (0 and 2.5 t ha −1 ; made from Eucalyptus wood) was integrated with urea (0 and 120 kg N ha −1 ) and green manure ( Tithonia diversifolia ; 0, 2.5 and 5 t ha −1 ) in a factorial design for four consecutive seasons from October 2012 to August 2014. Compared to the control, biochar increased soil CO 2 emissions (9–33%), reduced soil CH 4 uptake (7–59%) and reduced soil N 2 O emissions (1–42%) in each season, with no seasonal differences. N 2 O emissions increased following amendment with T. diversifolia (6%) and urea (13%) compared to the control. Generally, N 2 O emissions decreased where only biochar was applied. The greatest decrease in N 2 O (42%) occurred where all three amendments were applied compared to when they were added separately. EI in response to any of the amendments was lower than the control, ranging from 9 to 65% (33.0 ± 3.2 = mean ± SE). The amendments increased SOC stocks by 0.1–1.2 t ha −1 year −1 (mean ± SE of 0.8 ± 0.09 t ha −1 year −1 ). The results suggest decreased net EI with biochar in low fertility soils mainly through greater net primary productivity (89% of the decrease). [ABSTRACT FROM AUTHOR]

Green manure can be a source of nutrients for crops to spare some of the mineral fertilizer required for sustainable intensification of agriculture in smallholder context. We explored with a calibrated model the potential of legume green manure to help spare mineral fertilizer for sustainable intensification of rainfed rice production in Madagascar highlands. This study builds on a two-year rice experiment with rice and green manure as previous crop. The experiment investigated the response of rainfed rice growth to the incorporation into the soil of i) rice residue only (C:N ratio of 44.9) and ii) mucuna + crotalaria green manures (C:N ratio of 18.7). Two levels of fertilizer were investigated: manure only (5 t DM ha−1) (F1) and manure (5 t DM ha−1) in combination with mineral fertilizer (136 kg N ha−1) (F2). The crop model STICS was calibrated against observed soil water and soil mineral N, plant N uptake, aboveground biomass and grain yield to reproduce the impact of residue type and fertilizer input on mineralization of organic N in soil and in crop residue, crop growth and grain yield. The calibrated crop model was then used to explore rice response to mineral N fertilizer, with or without green manure, for the historical climate (1994–2018). Relative Root Mean Square Error (rRMSE) of model simulations fell within the observed relative variation in grain yield due to treatment effect. With green manure, mineral N available for rice increased compared with the situation without green manure, leading to greater agronomic use efficiency of N fertilizer. Green manure helped spare mineral fertilizer to achieve a reference yield set at 75 % of potential yield. This reference yield (3.67 t ha−1 on average across years) was reached with 40 kg N ha−1 with 6 t ha−1 of green manure, and 100 kg N ha−1 without green manure. The analysis of rice yield inter-annual variability indicated that (i) N leaching increased with total seasonal rainfall, which undermined the benefits of green manure on rice productivity in wetter years, and (ii) the increase in rice productivity allowed by the green manure did not fully compensate the rice yield foregone with the cultivation of the green manure. The calibrated model can be a useful tool to explore additional management strategies that will help maximize the benefit of green manure for sustainable intensification of rice-based cropping systems, especially in low-input cropping systems. • Impacts of green manure incorporation into the soil was assessed using modeling approach. • Rice response to mineral N fertilizer and green manure was evaluated with historical climate. • N available for crop increased with the use of green manure. • Green manure helped spare mineral fertilizer to achieve potential yield. • Benefits of green manure is undermined in wet years partly due to N leaching. [ABSTRACT FROM AUTHOR]

Melilotus officinalis is an important forage and green manure crop. There is a high degree of genetic diversity within species of M. officinalis. Despite the forage potential and the ability of nitrogen fixation, it has not been propagated in recent years because its high coumarin content. As a forage crop, the breeding goal of M. officinalis was mainly focused on improving forage yield and quality and reducing coumarin content. In this study, 25 superior half sib (HS) families of M. officinalis were used to carry out the second cycle recurrent selection, and genotypic variation of key traits (yield, quality and coumarin content) at two locations during 2018 and 2019 seasons were evaluated. Significant genotypic variation existed for the key traits: plant height (PH), dry biomass (DB), crude protein (CP), acid detergent fiber, neutral detergent fiber and coumarin. Also, significant genotype × location interactions were observed for the traits: DB, PH, CP, stem diameter, acid detergent lignin and acid insoluble ash (P < 0.05). Coumarin was negatively correlated with DB and PH, and positively correlated with CP. Genetic gain of all the traits of the second cycle recurrent selection were lower than that of the first cycle recurrent selection, except for PH and leaf/stem ratio (LSR). After the second cycle recurrent selection, the genetic gains of coumarin and LSR were higher than for other traits. Furthermore, new breeding lines generated by polycrossing superior HS families were evaluated. The polycrossing improved the yield and in vitro rumen fermentation characteristics and reduced the coumarin content. Our work provides new breeding lines of M. officinalis, beneficial for a sustainable grassland-based livestock industry. • Genotype × environment interactions affect yield and quality traits. • Recurrent selection process is useful to obtain plant materials with low coumarin content and high yield. • Superiority of new M. officinalis lines over currently grown demonstrated on fields and in vitro rumen fermentation. • We developed new breeding lines of M. officinalis beneficial for livestock industry. [ABSTRACT FROM AUTHOR]

Crop rotation and nitrogen (N) fertilization can influence soil N cycling, however, less is known about their interactive effects under varying soil and climatic conditions. We examined the interactive effects of preceding crops and N fertilizer rates on soil N cycling in canola ( Brassica napus L.) and spring wheat ( Triticum aestivum L.) cropping systems in no-till soils in the Canadian prairies. Field pea ( Pisum sativum L.), lentil ( Lens culinaris Medik), faba bean ( Vicia faba L.; faba bean-seed), canola and wheat grown for grain, and faba bean green manure (faba bean-GRM) were the preceding crops and were direct-seeded at 7 and 6 locations in 2009 and 2010, respectively. Canola and wheat were seeded in 2010 and 2011 (2012 for wheat at one site), respectively with N fertilizer applied at 0, 30, 60, 90 and 120 kg N ha −1 . Above-ground residue N returned was greatest for faba bean-GRM and lowest for canola and wheat. On average across sites, apparent in-crop N mineralization (ANM) under canola was greater following faba bean-GRM than all other preceding crops, except field pea, while under wheat, ANM was greater following all the legumes than following canola and wheat. Crop N uptake increased with N fertilizer rate, but the response was generally lower following faba bean-GRM and lentil. The N budget showed that 40–65% of crop N uptake (35–100% at highest ANM site) was possibly derived from ANM, more so following legumes, as compared to 35–60% from N fertilizer. The surplus and unaccounted N were particularly pronounced when canola and wheat were preceded by legumes rather than by canola or wheat. Our findings indicate that legumes can enhance soil N supply in no-till soils, and also highlight the importance of adjusting N fertilizer rates based on preceding crops to minimize the potential for N losses. [ABSTRACT FROM AUTHOR]

Rice–rice rotation is the most important intensive cropping system for food security in China. So far, few studies have examined sustainability of double-rice cropping system using partial substitution of fertilizer N (FN) by green manure (GM). The effects of 100% FN (N 100 ) and different substitution rates of FN by GM (80%, 60%, 40% and 20% FN plus 20%, 40%, 60% and 80% N through GM, and represented respectively by N 80 M 20 , N 60 M 40 , N 40 M 60 and N 20 M 80 ) on the rice productivity and N-supplying capacity of paddy soil were evaluated in double-rice system from 2008 to 2013. Soil organic matter and total N content in the 0–15 cm layer and rice grain yield of early and late rice annually increased in N 80 M 20 and N 60 M 40 plots, but decreased in N 100 , N 40 M 60 and N 20 M 80 plots. Compared with N 100 plots, the NH 4 + -N content and agronomic efficiency of applied N significantly increased in N 80 M 20 and N 60 M 40 plots. The grain yield and sustainable yield index of rice crops were improved in N 80 M 20 and N 60 M 40 plots, while declined in N 40 M 60 and N 20 M 80 . Soil NO 3 − -N content decreased significantly under partial substitutions of GM for FN. It can be concluded that the appropriate substitution of GM for FN (e.g., 20–40%) is beneficial for improving the productivity and sustainability of paddy field under double-rice cropping system. [ABSTRACT FROM AUTHOR]

Legume hairy vetch and non-legume barley mixtures are broadly cultivated to improve the value of cover crops in mono-rice paddies. Nevertheless, the effects of mixing conditions of the two cover crops on biomass and nutrient productivities and on the yield characteristics of subsequent rice crops have not been well studied. To evaluate the effects of mix-seeding legume and non-legume cover crops on the value of green manure in paddy soil, barley and hairy vetch were sown at the rice harvesting stage as pure crops at the recommended rates (180 kg ha −1 of barley, B100; 90 kg ha −1 of hairy vetch, V100), and as mixtures, in which the two cover crops were mix-seeded with varying seed ratios according to the replacement principle. The mixed seeding of the two crops significantly increased the cover crop biomass and nutrient productivities compared with the single barley and hairy vetch cultivation. Biomass productivity linearly increased with increasing barley seeding level, but it was not affected by the hairy vetch seeding rate. The total N content of the barley biomass clearly increased as the proportion of the total biomass accounted for by hairy vetch was increased, and this significantly improved the value of the green manure of cover crop biomass. In contrast, the total N content of the hairy vetch biomass was not affected by changes in the barley proportion. Biomass produced in the pure barley seeding could not produce the nutrients required by the recommended chemical fertilization level (N–P 2 O 5 –K 2 O = 90–45–57 kg ha −1 ) for rice, but the biomass increase caused by mixed seeding of the two cover crops resulted in enough nutrients to satisfy the recommended fertilization level. The highest biomass and nutrient yields were observed for the mixed seeding of barley and hairy vetch at 25 and 75% (B75V25) of their respective recommended seeding rates. This increased nutrient input stimulated the rice plant growth and significantly improved the rice yields. The highest yields were achieved with the B75V25 treatment. In conclusion, mixed seeding of legume hairy vetch and non-legume barley could be a very useful agronomic practice for increasing the cover crop biomass and its nutrient productivity and to improve the productivity of subsequent rice crops in temperate rice paddies. [ABSTRACT FROM AUTHOR]

Cover crop selection should be oriented to the achievement of specific agrosystem benefits. The cover crop, catch crop, green manure and fodder uses were identified as possible targets for selection. The objective was to apply multi-criteria decision analysis to evaluate different species ( Hordeum vulgare L., Secale cereale L., × Triticosecale Whim, Sinapis alba L., Vicia sativa L.) and cultivars according to their suitability to be used as cover crops in each of the uses. A field trial with 20 cultivars of the five species was conducted in Central Spain during two seasons (October–April). Measurements of ground cover, crop biomass, N uptake, N derived from the atmosphere, C/N, dietary fiber content and residue quality were collected. Aggregation of these variables through utility functions allowed ranking species and cultivars for each usage. Grasses were the most suitable for the cover crop, catch crop and fodder uses, while the vetches were the best as green manures. The mustard attained high ranks as cover and catch crop the first season, but the second decayed due to low performance in cold winters. Mustard and vetches obtained worse rankings than grasses as fodder. Hispanic was the most suitable barley cultivar as cover and catch crop, and Albacete as fodder. The triticale Titania attained the highest rank as cover and catch crop and fodder. Vetches Aitana and BGE014897 showed good aptitudes as green manures and catch crops. This analysis allowed comparison among species and cultivars and might provide relevant information for cover crops selection and management. [ABSTRACT FROM AUTHOR]

Abstract: The sustainability of crop production systems depends on the adoption of practices that allow the balancing of nutrient output and the preservation of soil organic matter. In Brazil, no-tillage (NT) is widely adopted for soybean-based cropping systems. In the Southern region, soybean alternates with maize in the summer and black-oats or wheat in the winter. Green-manure legumes are occasionally introduced in the crop rotation to break the continuous use of wheat in the winter. The objective of the present study was to evaluate if NT adoption would increase biological nitrogen fixation to soybean and other legumes. The hypothesis that a system richer in N would bring about positive effects on soil C stocks, was also tested. The study was carried out in Londrina, Paraná State, in Southern Brazil on a clayey Ferralsol that was cropped under NT with soybean as the main crop for more than 25 years. In 1997, three different crop rotations under both NT and conventional plough tillage (CT) were introduced. The crop rotations were composed of soybean, maize, wheat, black-oats and white lupins, but differed from each other in the frequency that each crop appeared in the rotation. Crop yields and the biomass of lupins and black-oats were quantified at every harvest during the 12 years of this study. Conversion factors of measured yield and biomass into C and biologically fixed N inputs to the crop system were developed from whole plant measurements performed in four of the twelve years of the study. The contribution of biological N2 fixation (BNF) to the legumes was determined using the ureide abundance and the 15N natural abundance techniques in 1998, 1999, 2005 and 2007. From these data, the calculation of N balance for each rotation (input N minus output N in harvested grain) was carried out. Soil C and N stocks to 80cm depth were quantified in 1997, 2003 and 2009. Grain yields were higher under NT for soybean and under CT for maize, in the rotation with the lowest frequency of legume crops. Soybean reliance on BNF was higher under NT (76%) than under CT (68%) whilst for lupins the reliance was 68% under NT and 60% under CT. The use of lupins as a green manure represented an extra contribution to soil N of approximately 300kgNha−1 and this was essential to maintain a positive N balance for the system. The comparison of soil C stocks between 1997 and 2009 revealed almost no gain in soil C under NT, but a C loss of 19MgCha−1 after 12 years of CT. Significant soil C and N losses were recorded in the rotation where lupins were planted more frequently and fertilizer N application to maize was suspended, which resulted in a very negative N balance for the system. The results highlight the importance of NT to enhance BNF inputs to the system and the need to recognize the N balance as a key driver of C stock changes in the soil. In addition, it suggests NT in this study had the consequence of avoiding soil C loss rather than increasing soil C stocks. [Copyright &y& Elsevier]

Abstract: Fields and Homegardens (representative of tropical smallholder extensive and intensive systems) were compared for soil quality and productivity of maize and mungbean in a hilly region of Sri Lanka (twinned 30 farms with Fields and Homegardens, each) over 2 years. The inclination categories were Flat (0–10%), Moderate (10–30%) and Steep (>30%). On half of the farms, green manure was added using Gliricidia leaves (3tonnesha−1 per season). Soil organic matter contents of Homegardens were at least 30% greater than in Fields, most pronounced in the Flat category. After 2 years of continuous maize and mungbean cropping in the major and minor rainy seasons, respectively, SOM generally declined; the greater depletion rate in Homegardens was positively correlated with crop yields. With recommended fertilizers (NPK), maize yield was always significantly higher in Homegardens than in Fields Flat and Moderate, this hold true at Steep lands only without NPK. Maize yield with NPK was on average two times higher than with Gliricidia alone, a respectable 4.5tonnesha−1 at Flat and Moderate, and 3.5tonnesha−1 even on Steep lands, seemingly the chemical soil fertility was more lacking than the physical properties. Gliricidia alone had no impact on yield in Fields but just in Homegardens, yield was increased by almost 30% in comparison to Zero fertilizer, an indication that chemical fertility was not directly supported by Gliricidia. Mungbean yields were generally less influenced by treatments, just the beneficial short term impacts of Gliricidia in Fields were relatively much higher than in maize. Conclusively, the long term input of organic manure in Homegardens was translated into a higher productivity in comparison to extensively managed Fields. However, the annual green manure supply supported yields mostly at marginal input levels and was overridden by mineral fertilizers independent of the inclination. Although, the usefulness of Gliricidia in degraded Steep lands was proven, the great risk of erosion remains in this landscape. Arable cropping there should be replaced by access to NPK on low inclined land once socio-economic conditions allow it. [Copyright &y& Elsevier]

Abstract: A 2-year field experiment was conducted in northern Greece to study the mulch effects of seven annual [anise (Pimpinella anisum L.), sweet fennel (Foeniculum vulgare P. Mill.), sweet basil (Ocimum basilicum L.), dill (Anethum graveolens L.), coriander (Coriandrum sativum L.), parsley (Petroselinum crispum (P. Mill.) Nyman ex A.W. Hill) and lacy phacelia (Phacelia tanacetifolia Benth.)] and three perennial [mint (Mentha X verticillata L.), oregano (Origanum vulgare L.) and common balm (Melissa officinalis L.)] aromatic plants, used as incorporated green manure, on the emergence and growth of barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.], common purslane (Portulaca oleracea L.), puncturevine (Tribulus terrestris L.), common lambsquarters (Chenopodium album L.) and maize (Zea mays L.). In addition, the phytotoxic potential of the abovementioned aromatic plants extracts was determined in the laboratory using a perlite-based bioassay with maize and barnyardgrass. The bioassays indicated that germination, root elongation and fresh weight of barnyardgrass were reduced by the most aromatic plant extracts. However, maize growth parameters were only affected by the extracts of anise, sweet fennel, coriander, common balm and oregano. In the field, emergence of barnyardgrass, common purslane, puncturevine or common lambsquarters was reduced by 11–50%, 12–59%, 26–79% or 58–83% in green manure-treatment plots, respectively, as compared with green manure-free plots (control). On the contrary, maize emergence was not affected by any green manure. At harvest, maize grain yield in green manure-herbicide untreated plots was 10–43% greater than that in the corresponding green manure-free plots. In particular, maize grain yield in anise, dill, oregano or lacy phacelia green manure-herbicide untreated plots was 27–43% greater than that in the green manure-free-herbicide untreated and slightly lower than that obtained in the corresponding herbicide treated plots. These results indicated that green manure of aromatic plants, such as anise, dill, oregano or lacy phacelia could be used for the suppression of barnyardgrass and some broadleaf weeds in maize and consequently to minimize herbicide usage. [Copyright &y& Elsevier]

• Both Δ Y R and Δ WUE R in the LGM systems were over 5% when rainfall was adequate. • Soil in the LGM systems was 39.7 % times more desiccated than that in the fallow system. • LGMs yielding ≥1926 kg ha−1 reduced wheat yield in this dry-land region. • The safety threshold of soil water consumption by the LGMs was 26.2 mm (0−200 cm). • The minimum annual rainfall for applying the LGM approach was estimated to be 551 mm. The growth of leguminous green manure (LGM) in place of bare fallow in summer improved soil fertility but resulted in reduced soil water storage and crop yield in semiarid regions of the Loess Plateau. To balance the contradiction between yield production and soil water consumption in LGM systems, we investigated the effects of replacing fallow with three LGMs on the relative changes in grain yield and water use efficiency of winter wheat (Triticum aestivum L.), the plant available water distribution pattern, and the soil desiccation characteristics in the 0−200 cm layer from 2009 to 2018. Additionally, we assessed the correlations between Δ soil water storage, LGM biomass, and annual precipitation with Δ grain yield, and Δ soil water storage with LGM biomass over 10 years. Results showed that the relative changes in wheat yield and water use efficiency in the LGM systems were all negative in a dry year, however, they were all positive and over 5 % when rainfall was adequate. There were strong positive correlations between the annual precipitation with Δ soil water storage (R2 =0.59) and Δ grain yield (R2 =0.67). The minimum annual rainfall for applying the LGM approach was estimated to be 551 mm. Conversely, the slight correlations between the LGM biomass with Δ soil water storage (R2 =0.125*) and Δ grain yield (R2 =0.25**) under the LGM systems were all negative. Compared to the fallow system, for every 71.4 kg ha−1 of LGM aboveground biomass produced, the soil water storage during the fallow period was reduced by 1 mm, and for 1 mm of soil water storage decreased, the wheat yield was reduced by 18.9 kg ha−1 in the LGM systems. Consequently, managing the LGM aboveground biomass within 1926 kg ha−1 or less may be an efficient option to reduce the risks of wheat yield and soil water balance due to replacing fallow with LGMs on the Loess Plateau and in similar dry-land regions. [ABSTRACT FROM AUTHOR]

Abstract: Biological nitrogen fixation (BNF) as a result of the legumes–rhizobia symbioses is the main source of nitrogen in organic farming systems. Lucerne (Medicago sativa L.), used as green manure or as forage legume, is important on arable farms under dry site conditions. In a field experiment on organically managed agricultural fields, we examined the impacts of the utilisation system (harvested=forage production versus mulched=green manure) and the crop composition (pure lucerne crops versus lucerne–grass mixtures) on yield, biological nitrogen fixation (BNF), soil inorganic N content, N balance and water consumption of autumn-cultivated lucerne crops. The study was conducted at the University of Natural Resources and Applied Life Sciences, Vienna, in eastern Austria—a region characterized by pannonian site conditions (9.8°C mean annual temperature, 545mm average total precipitation) and stockless farming systems. Our results indicate that the utilisation system and the crop composition had no marked influence on above- and below-ground dry matter (DM) and N yield, soil inorganic N contents, BNF, or water use efficiency of lucerne. The level of symbiotically fixed N2 in harvested lucerne was 89–125kgNha−1 (27–33% Ndfa=nitrogen derived from atmosphere) in the first year and 161–175kgNha−1 (47–49% Ndfa) in the second year of the study. The high soil inorganic N supply in the first year increased the N uptake from soil by lucerne and led to a reduced BNF. Under the dry and unfavourable conditions in both study years, the nitrogen release from the legume mulch was retarded and BNF in mulched lucerne was not reduced. Assuming low gaseous N losses by mulching (15–30kgNha−1), the green manure system reached a positive N balance (+137 to +186kgNha−1) for the subsequent crops because abundant residues remained on the field. [Copyright &y& Elsevier]

Velvet bean (Mucuna pruriens (L.) DC cv. group utilis) is widely promoted as a GMCC for tropical regions. Reports of insufficient biomass production in certain environments and concerns over seed production, however, suggest a need for a more complete description of growth and development of velvet bean under different production scenarios and environments. Process-based simulation models offer the potential for facilitating an assessment of management strategies for different environments, soils and production systems. The objective of this study was to review the physiology of velvet bean and using the generic legume model CROPGRO, to provide a structured and quantitative framework for describing crop response to management and environment. Model coefficients used to describe growth and development of soybean (Glycine max (L.) Merr.) served as initial reference values. Information on velvet bean from published sources was then used to revise the functions and parameters of the model. Phenology, canopy development, growth and partitioning were calibrated for two velvet bean varieties using experimental data from three sites in Mexico. Compared to soybean, velvet bean has a much longer growth cycle, allowing a very large numbers of nodes to form. Velvet bean has larger, thinner leaves than soybean, resulting in more rapid leaf area development, and larger seeds, which affects germination, early season growth and pod development. A modification to CROPGRO to track senesced tissues was incorporated. Overall, the physiological processes underlying growth and development of velvet bean appear to be similar to other tropically adapted legumes. The new model, incorporated as part of the DSSAT, version 3.5 suite of crop simulation models, has potential for evaluating management strategies in specific environments and to identify potential regions for introduction of velvet bean as a green manure cover crop. [Copyright &y& Elsevier]

Integrated use of organic and inorganic fertilizers can improve crop productivity and sustain soil health and fertility. The present research was conducted to study the effects of application of green manures [sesbania (Sesbania aculeate Poiret) and crotalaria (Crotalaria juncea L.)] and farmyard manure on productivity of rice (Oryza sativa L.) and its residual effects on subsequent groundnut (Arachis hypogaea L.) crop. Rice and groundnut crops were grown in sequence during rainy and post-rainy seasons with and without green manure in combination with different fertilizer and spacing treatments under irrigated conditions. The results showed that application of green manures sesbania and crotalaria at 10 t ha−1 to rice compared to no green manure application significantly increased grain yield of rice by 1.6 and 1.1 t ha−1, and pod yields of groundnut crop succeeding rice by 0.25 and 0.16 t ha−1, respectively. There was no significant difference between the application of crotalaria or farmyard manure at 10 t ha−1 on grain yields of rice, but pod yields of subsequent groundnut crop were greater with application of green manure. There was no significant effect of different spacing 20×15,15×15,15×10 cm2 (333 000; 444 000; 666 000 plant ha−1, respectively) on grain yield of rice. Pod yields of groundnut were significantly greater with closer spacing 15×15 cm2 (444 000 plants ha−1) as compared to spacing of 30×10 cm2 (333 000 plants ha−1). Maximum grain of rice was obtained by application of 120:26:37 kg NPK ha−1 in combination with green manures, whereas maximum pod yield of groundnut was obtained by residual effect of green manure applied to rice and application of 30:26:33 kg NPK ha−1 in combination with gypsum applied to groundnut crop. [Copyright &y& Elsevier]

• Short term fallows enhance productivity, improve soil fertility and serve dual purpose in crop-livestock systems. • Green manuring increased wheat grain yield by 18–26 % over mineral fertilizers. • Root biomass of green manures alone increased yield of subsequent crop by 25 %. • Green manuring improved soil water, soil pH, organic carbon and nutrients. • Residual effect of green manuring compensates 33 % of N demands of wheat. Soil fertility depletion is a major constraint of smallholder farming in sub-Saharan Africa. We tested the aftereffects of green manures, namely vetch (Vicia sativa L.), lupin (Lupinus polyphyllus L.), and lablab (Lablab purpureus L.) incorporated into the soil compared to three fertilizer levels (0/0, 23/0, and 78/20 kg N/P ha−1) and evaluated their effect on soil fertility status and wheat yield in acidic Nitisols of southern Ethiopia, for three consecutive years (2017–2019). The treatments were laid out in a randomized complete block design with three replications. In 2017 and 2018, green manures were sown in March and April, respectively, using short rains and incorporated into the soil during late flowering stage, either (i) the whole shoot and root biomass were plowed under, (ii) shoot biomass was transferred to non-treated plots or (iii) only the below ground root biomass was used. Wheat was sown during long rains during the same growing season a month after the incorporation of green manures. In 2019, wheat was grown on the residual plots with the application of an additional 64/20 kg N/P ha−1. Results revealed that in 2017 and 2018 the application of vetch and lupin green manure resulted in grain yield advantages of 49 and 32 % and 34 and 19 %, respectively, over 0/0 and 23/0 kg N/P ha−1, though it produced less grain yield compared to higher fertilizer rates. In 2019, the addition of vetch and lupin whole biomass treatments gave significantly higher wheat yield over fertilizer treatments, with yield advantages of 18–26 %. Similarly, root biomass only also produced a significantly higher yield than fertilized plots. The yield benefits from green manures were due to improved soil water content, improved P-availability, significantly increased exchangeable K, Ca, and Mg, and increased pH by about 0.5 units. The residual effect of green manures could compensate for up to 33 % of the recommended rate of 78 N kg ha−1. We conclude that niche-based integration of green manures could improve yield, enhance soil carbon sequestration and sustain crop-livestock systems, whereby the above ground biomass could serve as quality livestock feed without compromising soil fertility benefits. [ABSTRACT FROM AUTHOR]

• Evaluation of green manure application effect by meta-analysis. • Green manure can significantly improve soil nutrient content. • Green manures' type affects succeeding crops yield. The application of green manure is a traditional and valuable practice for agroecosystem management. In northern China, the effects of green manure on production of the region's major crops have been extensively investigated, but the inconsistent conclusions that these case studies have yielded cannot provide effective guidance for practical local agricultural production. Here, we conducted a meta-analysis to generate a comprehensive evaluation of the effects of green manure on soil properties and crop yield in this region. Our results shown that green manure improves soil quality effectively, decreasing soil bulk density by ∼ 5.6 %, increasing microbial biomass carbon by 28 %, and improving the activities of soil enzymes by 14 % ∼ 39 %. Among the different types of green manure, legume green manure more markedly increased both nitrate and hydrolysable nitrogen, while non-legume green manure more markedly increased available potassium. Soil gravimetric water content was decreased under green manure treatment. Maize yield was significantly increased under green manure by 11 % on the whole, while effects of green manure on wheat and potato were inconsistent. In summary, the application of green manure in northern China can improve soil quality significantly, and proper green manure use can improve cash crop yields. [ABSTRACT FROM AUTHOR]

• Covariates associated with mean and variance of wheat and rye yield were investiagted. • Mixed models served to identify mean and variance trends associated with covariates. • Mean yield affected by water availability in different stages of the generative phase. • Yield variance was found to increase with the calendar year for both crops. • Coefficient of variation decreased for wheat and increased for rye with time. There is considerable interest in assessing genetic gain from breeding efforts, as well as trends from non-genetic sources such as climate change. Long-term data from official variety trials provide an ideal opportunity to do so. Whereas past work on the subject was mainly focussed on trends in mean performance, little attention has been paid to yield stability. The purpose of the present paper therefore is to provide a framework for assessing trends in stability and to exemplify this using long-term data from German variety trials. Specifically, trends in the mean and variance of winter wheat and winter rye yields associated with genotypic, spatial, and climatic covariates were investigated based on a long-term series of multi-environment trials from 1983/1985 to 2016. Yield stability is assessed based on the variance of yield. For climatic covariates, trends were investigated using growth stage-specific covariates which were obtained by dividing the total growth period into five or ten growth stages within which covariates were aggregated. The analysis was done by linear mixed models and forward selection served to identify trends in mean and variance. Specifically, trends in the mean were selected based on a coefficient of determination, R 2 , while variance trends associated with a covariate were selected based on the change in variance attributable to the covariate. For spatial covariates, mean yield increased with the field capacity in up to one meter soil depth in case of rye. For both crops, mean yield was negatively affected by a deficit in available water during the development of vegetative parts while water deficit towards the end of the growth period was positively associated with mean yield. Trends were also selected accounting for interactions of climatic covariates and genotypic groups (wheat: quality type; rye: breeding type), revealing that R 2 generally increased when interactions were taken into account. The responses to covariates were similar for the different groups, meaning the increase in R 2 is mainly attributable to the main effects of the genotypic groups. Variance trends associated with the calendar year were identified for both crops, revealing yield variance slightly increased with time. Based on the selected model, a coefficient of variation was obtained for each year to assess relative yield stability, showing a decrease for wheat and an increase for rye. [ABSTRACT FROM AUTHOR]

• N surplus under the conventional PBC rotation was significantly higher than the alternative PSB rotation. • Nitrogen surplus was strongly correlated with leachate N concentration. • Potato and red clover phases produced most of the N leaching during the rotations. • Conventional practice of amending red clover as green manure poses a high risk to the environment. • Potato yield following the PSB rotation was 13.4% higher than the PBC rotation. Elevated nitrate levels in surface and ground waters on Prince Edward Island (PEI), Canada, are of concerns for both drinking water quality and aquatic habitat protection. These elevated nitrate levels have been closely linked to excessive nitrogen (N) leaching from land under intensive potato production. An improved understanding of the effects of conventional and alternative potato rotation systems and associated rotation crops on N leaching and potato tuber yield is needed to inform if the alternative rotation can impose less impact on water quality while maintaining the economic viability. We contrasted two field based, 3-year potato-based rotations: a potato-barley-red clover (PBC) rotation (conventional), and a potato-soybean-barley (PSB) rotation (alternative), from 2014 to 2017. Crop tissue N accumulation, soil mineral N and N concentrations in soil leachate were measured during the experimental period for assessing N dynamics and potential N leaching loss from the two systems. On a rotation basis, soil mineral N and N concentrations in leachate under the PBC rotation were significantly higher when compared with the PSB rotation after the planting of red clover. The overall N utilization efficiency of the PSB rotation was 1.6 times to that of the PBC rotation. Due to the high N surplus during the red clover and potato phase, total N surplus of the PBC rotation across the 3 years was significantly higher than that of the PSB rotation. A strong positive correlation was found between nitrogen surplus and average seasonal leachate nitrate concentration. On rotation crop level, potato and red clover phases produced most of the potential N leaching loss during the rotation cycles. The red clover phase accumulated the largest amount of N and produced the largest amount of N loss when compared with other rotation crops. Nitrogen leaching occurred primarily in the non-growing season, with different rotation crops demonstrating different leaching patterns. In the potato phase, N leaching occurred primarily between October and late December. Nitrogen leaching sourced from the red clover spanned a long-lasting process: the high mineralization rate and extended mineralization period of the residue led to carry-over of N leaching into the subsequent growing season. In addition, potato yield following the PSB rotation was 13.4% higher than the PBC rotation in 2017. These data suggested that the alternative PSB rotation could increase potato yields while reducing N leaching compared to the conventional PBC rotation. [ABSTRACT FROM AUTHOR]