Cereal Cropping Systems Research Articles

Exploring the effects of extreme events on cereal cropping systems in the Ganga River basin, Haryana

ABSTRACT Recent studies have highlighted the profound impact of global warming on climate patterns worldwide, but few have specifically addressed its consequences for crop yields. This study aims to bridge that gap by examining the trends of extreme events and their effects on agriculture in adjacent Ganga River Basin Haryana districts from 1981 to 2020, focusing on the Expert Team on Climate Change Detection, Monitoring and Indices. The study area experienced increasing mean maximum and minimum temperatures, raising drought concerns, especially in Sonipat and Panipat districts. Drought indices showed prolonged events in these areas, contrasting with shifting wet-dry patterns in Yamuna Nagar and fluctuating conditions in Karnal. An analysis from 1998 to 2020 revealed intricate relationships between climate factors and rice, wheat, and pearl millet production, with rising temperatures significantly impacting crop yields. Notably, both mean maximum and minimum temperatures have increased, with a significant daytime and nighttime warming trend. Extreme maximum temperature and diurnal temperature range indices were found to negatively impact crop yields, whereas precipitation extremes demonstrated positive correlations with yield outcomes. Collaborative efforts between policymakers and farmers to integrate climate-resilient practices and continuous monitoring are crucial for ensuring food security and sustainable farming amidst climate variability.

Potassium limits productivity in intensive cereal cropping systems in Southeast Asia.

Potassium (K) has received little attention as a potential yield-limiting factor in cropping systems. Here we investigated the K status in intensive cereal cropping systems in Indonesia, which are representative of many other Southeast Asian countries. Our analysis included nutrient input-output balance, leaf nutrient status, long- and short-term fertilizer trials, and farmer surveys. We revealed that soil K levels alone are insufficient to meet plant requirements, and current fertilizer applications are inadequate to prevent K deficiencies and large negative annual soil K balances in farmer fields (average -62 kgK ha-1). On-farm fertilizer trials indicated that nearly 80% of rice crops and 70% of maize crops achieved higher yields with the application of K fertilizer. Addressing K limitations will require an enhanced capacity to predict crop responses to K fertilizer, together with long-term, flexible fertilizer and crop residue management strategies. Furthermore, similar K limitations have probably emerged in other regions globally due to intensive cropping with insufficient K replenishment, which must be addressed to close yield gaps on existing farmland.

Amorphous silica fertilization ameliorated soil properties and promoted putative soil beneficial microbial taxa in a wheat field under drought

Increasing water demand from agricultural practices and environmental pollution caused by the intensive use of agrochemicals are among the most pressing issues concerning agriculture sustainability. The use of amorphous silica (ASi) as soil amendment can represent a valid alternative measure to cope with the upcoming challenges of intensifying drought stress and to decrease the need for phosphorus fertilizer application. In this study, we investigated the impact of two levels of ASi fertilization on edaphic characteristics and the rhizosphere microbiota of winter wheat through a field experiment conducted during a drought period. Since plant phenology plays a pivotal role in shaping crop microbiota, our research explored the response of rhizosphere bacteria and fungi to ASi fertilization at three distinct stages of plant growth: pre-planting, tillering, and ripening. Firstly, our results clearly showed an ameliorative effect of ASi fertilization on edaphic properties, with notable improvements in soil moisture, particularly at higher ASi fertilization levels. Secondly, we observed that ASi exerted a profound influence on the wheat microbiota, resulting in varying effects on bacterial and fungal communities. Specifically, in comparison to the control treatment, bacterial community composition exhibited greater sensitivity to ASi fertilization during the tillering stage, whereas the fungal microbiota displayed increased dissimilarity during the ripening stage. Notably, ASi fertilization promoted in the wheat rhizosphere the enrichment of plant-beneficial microbes with putative plant-growth promoting and biocontrol capabilities. Overall, our findings highlight the efficacy of ASi fertilization as an effective measure to mitigate drought stress, enhance the availability of plant nutrients, and promote the enrichment of beneficial microbes within cereal cropping systems.

Sustainable intensification of sorghum-based cropping systems in semi-arid sub-Saharan Africa: The role of improved varieties, mineral fertilizer, and legume integration

ProblemSustainable intensification of cereal cropping systems can contribute to reducing food insecurity while mitigating biodiversity losses thanks to land sparing. Yet, intensifying crop production with more nutrient inputs often increases sensitivity to climate hazards and yields inter-annual variability. How different options for sustainable intensification interact and how they could help achieve greater and less variable yields is not well known for key cereal cropping systems of sub-Saharan Africa. ObjectiveHere, we aim to assess the impact on productivity and its interannual variation of three contrasted strategies of crop intensification, namely i) the integration of cowpea intercropped with sorghum or as sole crop, ii) improved varieties with high harvest index and greater nitrogen use efficiency, and iii) the use of more mineral fertilizer. MethodsWe did this assessment using a calibrated soil-crop model for a case study of sorghum-based cropping systems of semi-arid southern Mali, using a historical weather series from 1980 to 2010. ResultsWe found that the incremental combinations of two or three strategies helped increase productivity in terms of energy and protein. However, greater productivity went hand in hand with greater inter-annual variability. Intercropping sorghum with cowpea helped to reduce the inter-annual variability of productivity, but only when mineral fertilizer was not added. With mineral fertilizer input, sorghum contributed the largest share of the intercrop productivity, and sorghum yield was more variable from a year to another than cowpea yield. The overall productivity of intercropping sorghum with cowpea was always greater than having the two sole crops on separate plots. This was possible thanks to the facilitation of light, water and N acquisition by the two crops in the intercropping, regardless of the specificities of the growing season with regard to water and nitrogen stress. However, the variability of productivity was smaller for the cultivation of the two sole crops on separate plots, regardless of fertilizer input. ConclusionThe often-claimed benefit of intercropping on reducing the inter-annual variability of production does not hold when the three strategies are combined. ImplicationsOur results suggest that the integration of legumes does not help cushion farmers against the risk related to the intensification of cropping systems with more nutrients and improved seeds. Careful gross margin analysis that accounts for price variability and uncertainty would be required to refine this risk assessment for specific farm contexts. We discuss the implication of these findings in light of the current research agenda for the sustainable intensification of cropping systems in sub-Saharan Africa.

A redistribution of nitrogen fertiliser across global croplands can help achieve food security within environmental boundaries

A major societal challenge is to produce sufficient food for a growing global population while simultaneously reducing agricultural nitrogen pollution to within safe environmental boundaries. Here we use spatially-resolved, process-based simulations of cereal cropping systems (at 0.5° resolution) to show how redistribution of nitrogen fertiliser usage could meet this challenge on a global scale. Focusing on major cereals (maize, wheat and rice), we find that current production could be (i) maintained with a 32% reduction in total global fertiliser use, or (ii) increased by 15% with current nitrogen fertiliser levels. This would come with substantial reductions in environmental nitrogen losses, allowing cereal production to stay within environmental boundaries for nitrogen pollution. The more equal distribution of nitrogen fertiliser across global croplands would reduce reliance on current breadbasket areas, allow regions such as Sub-Saharan Africa to move towards self-sufficiency and alleviate nitrogen pollution in East Asia and other highly fertilised regions.

Physiological and Molecular Analysis Revealed the Role of Silicon in Modulating Salinity Stress in Mung Bean

Salinity stress acts as a significant deterrent in the course of optimal plant growth and productivity, and mung bean, being a relay crop in the cereal cropping system, is severely affected by salinity. Silicon (Si), on the other hand, has exhibited promising outcomes with regards to alleviating salinity stress. In order to understand the critical mechanisms underlying mung bean (Vigna radiata L.) tolerance towards salt stress, this study examined the effects of different salinity concentrations on antioxidant capacity, proteome level alterations, and influence on Si-transporter and salt-responsive genes. Salinity stress was seen to effect the gaseous exchange machinery, decrease the soluble protein and phenolic content and NR activity, and increase the accumulation of reactive oxygen species. An efficient regulation of stomatal opening upon Si application hints towards proficient stomatal conductance and CO2 fixation, resulting in efficient photosynthesis leading to proficient plant growth. The soluble protein and phenolic content showed improved levels upon Si supplementation, which indicates an optimal solute transport system from source to sink. The content of superoxide radicals showed a surge under salinity stress treatment, but efficient scavenging of superoxide radicles was noted under Si supplementation. Salinity stress exhibited more damaging effects on root NR activity, which was notably enhanced upon Si supplementation. Moreover, the beneficial role of Si was further substantiated as there was notable Si accumulation in the leaves and roots of salinity-stressed mung bean plants. Furthermore, Si stimulated competent ROS scavenging by reinforcing the antioxidant enzyme activity, as well coordinating with their isozyme activity, as expressed by the varying band intensities. Similarly, the Si-mediated increase in peroxidase activity may reveal changes in the mechanical characteristics of the cell wall, which are in turn associated with salinity stress adaptation. Proteomic investigations revealed the upregulation or downregulation of several proteins, which were thereafter identified by LC−MS/MS. About 45 proteins were identified and were functionally classified into photosynthesis (24%), metabolic process (19%), redox homeostasis (12%), transmembrane transport (10%), stress response (7%), and transcription regulation (4%). The gene expression analysis of the silicon transporter genes (Lsi1, Lsi2, and Lsi3) and SOS pathway genes (SOS1, SOS2, and SOS3) indicated the role of silicon in mitigating salinity stress. Hence, the findings of this study can facilitate a profound understanding of the potential mechanisms adopted by mung bean due to exogenous Si application during salinity stress.

Companion crops alter olfactory responses of the fall armyworm (Spodoptera frugiperda) and its larval endoparasitoid (Cotesia icipe)

BackgroundThe fall armyworm (FAW), Spodoptera frugiperda, is a devastating invasive pest and a threat to food security in Africa, with yield losses of 20–50%. Recent studies highlighted the importance of cereal crops such as maize and sorghum as the most preferred host plants for FAW oviposition. In the current work, we investigated the olfactory responses of FAW and its key larval endoparasitoid Cotesia icipe to odours from the preferred host (maize) in the presence of six potential companion crops including beans, groundnut, sweet potato, greenleaf- and silverleaf desmodium, and cassava. We hypothesized that odours released by companion crops in maize-based intercropping systems would alter host preferences of FAW for oviposition and its parasitoid responses.ResultsIn dual choice oviposition bioassays, FAW laid significantly more eggs on maize than on the other plants. However, in the multiple-choice bioassays, significantly fewer eggs were laid on maize when companion plants were present except cassava. While wind tunnel bioassays confirmed the differential behavioural responses of FAW, we found that its larval endoparasitoid C. icipe was attracted to volatiles from the companion plants tested individually and/or when they were combined with maize. Coupled gas chromatography–mass spectrometry (GC–MS) analysis detected several potential behaviour-modifying compounds including (Z)-3-hexenyl acetate, (E)-β-ocimene, (E)-4,8-dimethyl-1,3,7-nonatriene, (E)-β-caryophyllene, camphor, methyl salicylate and (E, E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene.ConclusionsOur findings provide evidence supporting diversified maize cropping system could reduce FAW damage by repelling the pest while simultaneously recruiting its natural enemies. Hence, diversifying cereal cropping system with companion crops could serve as an ecologically sustainable FAW management strategy.Graphical

Domestic Herbivores, the Crucial Trophic Level for Sustainable Agriculture: Avenues for Reconnecting Livestock to Cropping Systems

Domestic herbivores have been closely associated with the historical evolution and development of agriculture systems worldwide as a complementary system for providing milk, meat, wool, leather, and animal power. However, their major role was to enhance and maintain agricultural soil fertility through the recycling of nutrients. In turn, cereal production increased, enabling to feed a progressively increasing human population living in expanding urban areas. Further, digestion of organic matter through the rumen microbiome can also be viewed as enhancing the soil microbiome activity. In particular, when animal droppings are deposited directly in grazing areas or applied to fields as manure, the mineralization–immobilization turnover determines the availability of nitrogen, phosphorus, potassium, and other nutrients in the plant rhizosphere. Recently, this close coupling between livestock production and cereal cropping systems has been disrupted as a consequence of the tremendous use of industrial mineral fertilizers. The intensification of production within these separate and disconnected systems has resulted in huge emissions of nitrogen (N) to the environment and a dramatic deterioration in the quality of soil, air, and ground- and surface water. Consequently, to reduce drastically the dependency of modern and intensified agriculture on the massive use of N and phosphorus (P) fertilizers, we argue that a close reconnection at the local scale, of herbivore livestock production systems with cereal-based cropping systems, would help farmers to maintain and recover the fertility of their soils. This would result in more diverse agricultural landscapes including, besides cereals, grasslands as well as forage and grain crops with a higher proportion of legume species. We developed two examples showing such a beneficial reconnection through (i) an agro-ecological scenario with profound agricultural structural changes on a European scale, and (ii) typical Brazilian integrated crop–livestock systems (ICLS). On the whole, despite domestic herbivores emit methane (CH4), an important greenhouse gas, they participate to nutrient recycling, which can be viewed as a solution to maintaining long-term soil fertility in agro-ecosystems; at a moderate stocking density, ecosystem services provided by ruminants would be greater than the adverse effect of greenhouse gas (GHG).

Biomass and Methane Production in Double Cereal Cropping Systems with Different Winter Cereal and Maize Plant Densities

The biogas supply chain requires a correct combination of crops to maximize the methane yield per hectare. Field trials were carried out in North Italy over three growing seasons, according to a factorial combination of four cropping systems (maize as a sole-crop or after hybrid barley, triticale and wheat) and two maize plant densities (standard, 7.5 plants m−2 and high, 10 plants m−2) with the plants harvested as whole-crop silage. The specific methane production per ton was measured through the biochemical methane potential (BMP) method, while the methane yield per hectare was calculated on the basis of the BMP results and considering the biomass yield. The average methane yield of wheat resulted to be equal to 4550 Nm3 ha−1, and +17% and +28% higher than triticale and barley, respectively, according to the biomass yield. A delay in maize sowing reduced the yield potential of this crop; the biomass of maize grown after barley, triticale and wheat was 20%, 33% and 47% lower, respectively, than maize cultivated as a single crop. The high plant population increased the biomass yield in the sole-crop maize (+23%) and in the maize grown after barley (+20%), compared to the standard density. The highest biomass (32 t ha−1 DM) and methane yield (9971 Nm3 ha−1) within the cropping systems were obtained for barley followed by maize at a high plant density. This cropping system increased the methane yield by 46% and 18%, respectively, compared to the sole-crop maize or maize after triticale at a standard density. The smaller amount of available solar radiation, resulting from the later sowing of maize, reduced the advantage related to the application of a high plant density.

How different is the remediation effect of biochar for cadmium contaminated soil in various cropping systems? A global meta-analysis

Cadmium (Cd) poses great threats to human health as a major contaminant in agricultural soil. Biochar shows great potential in the remediation of agricultural soil. However, it remains unclear whether the remediation effect of biochar on Cd pollution is affected by various cropping systems. Here, this study used 2007 paired observations from 227 peer-reviewed articles and employed hierarchical meta-analysis to investigate the response of three types of cropping systems to the remediation of Cd pollution by using biochar. As a result, biochar application significantly reduced the Cd content in soil, plant roots and edible parts of various cropping systems. The decrease in Cd level ranged from 24.9% to 45.0%. The feedstock, application rate, and pH of biochar as well as soil pH and cation exchange capacity were dominant factors for Cd remediation effect of biochar, and their relative importance all exceeded 37.4%. Lignocellulosic and herbal biochar were found to be suitable for all cropping systems, while the effects of manure, wood and biomass biochar were limited in cereal cropping systems. Furthermore, biochar exhibited a more long-lasting remediation effect on paddy soils than on dryland. This study provides new insights into the sustainable agricultural management of typical cropping systems.

Seed row placement relative to the previous crop stubble row can harness systems benefits on water repellent sands

Context Innovations to improve crop establishment are critical to unlocking the full potential of early sown winter cereal cropping systems. Aims The aim of this set of experiments was to evaluate the systems benefits of near-row sowing treatments for surface soil water, crop establishment, crop competition with weeds, root disease infection and cereal crop yield on sandy soils in low-rainfall environments. Methods Six of the 10 site–years evaluated were on water repellent sands with the remainder on sand and loam. A second set of experiments on a water repellent sand evaluated if furrow applied amendments to increase soil fertility in the crop row might generate additional benefits to the near-row sowing effect. Key results Significant grain yield benefits from near-row placement (up to 30%) were measured in 2 site years and these were associated with crop establishment gains, improved access to furrow soil water storage and weed seed reductions, which occurred in 3 site years. In a water repellent sand, near-row placement combined with extra nutrition input generated an additional grain yield benefit (+0.4 t/ha), as did a one-off 22 cm deep furrow tilling treatment designed to bring deeper soil moisture into the seed zone (+0.4 t/ha). Conclusions Near-row placement of crop seeds can provide systems benefits in water repellent sands. The conversion of these benefits to yield benefits occurred in 30% of site-years tested on repellent sand. Implications Further innovation is required to ensure that these seeder-based innovations generate predictable responses and scaled up evaluation is necessary to fully understand the systems and landscape level benefits of improved crop establishment in soils that often suffer low and uneven crop establishment numbers.

Allelopathic Effect of Barley (Hordeum vulgare) and Rapeseed (Brassica napus) Crops on Early Growth of Acetolactate Synthase (ALS)-Resistant Glebionis Coronaria

Glebionis coronaria is a serious threat to cereal production in Northern Tunisia. Previous results showed that G. coronaria has developed resistance to acetolactate synthase (ALS)-inhibiting herbicides which limits their use in cereal cropping systems. The use of allelopathic crops has been reported as a potential alternative to herbicides to control resistant weed populations. The aim of this study is to evaluate the effect of five allelopathic crops on the early growth of G. coronaria. In vitro experiments using aqueous extracts of different crops and in pots experiments with increasing rates of barley (Hordeum vulgare) and rapeseed (Brassica napus) residues were performed for this purpose. All tested crops showed allelopathic effects on G. coronaria and were able to reduce its root length at the concentration of 50 g/L. Barley and rapeseed were the most effective crops, with 70% and 60% of root length reduction, respectively. An aqueous extract concentration study with five increasing concentrations of 12.5, 25, 50, 75, and 100 % was performed with these two crops, and root length was significantly reduced with increasing concentration, being up to 80% with the highest aqueous extract concentration of barley. The in vitro results were supported by the in pots experiment: Shortest roots length and highest dry mass reduction were obtained by the highest barley (0.64 g/kg) and rapeseed (8 g/kg) residue concentrations. This study confirmed the allelopathic potential of both barley and rapeseed in reducing the early growth of ALSresistant G. coronaria, suggesting the effectiveness of these crops if integrated with other control measures for the management of resistant population of G. coronaria in cereal fields.

Comparison on environmental impacts of cereal and forage production in the Loess Plateau of China: Using life cycle assessment with uncertainty and variability analysis

The increasing demand for high-quality animal protein calls for parts of cereal cropping systems converting to forage or forage-livestock integrated systems. This study aimed at evaluating potential environmental impacts of this transition at the farm level on the Loess Plateau of China through a life cycle assessment (LCA) approach. Four dominating crops: alfalfa, wheat, grain maize and silage maize were studied based on the ten impact categories. Based on standard unit land area (1 ha) and timestamp (2018–2020) settings, alfalfa production indicated the lowest environmental impact in nine categories compared to other crops, while wheat indicated better performance in seven of ten impact categories than other crops except alfalfa. With respect to the environmental loads of grain maize and silage maize production, both systems were very comparable. Because of the common adoption of open-land burning of straws (mainly for fuel and winter heating) in the local region, the respiratory inorganics and photochemical oxidant formation potential impact of alfalfa and silage maize per hectare produced is much lower than those of wheat and grain maize. Great differences in environmental impacts between the two types of cropping systems (cereal vs forage) indicate that transitioning from cereal to forage production should effectively reduce air pollution and enhance environmental sustainability on the Loess Plateau. Besides, uncertainty and variability of LCAs results were analyzed in this study.

Nitrous Oxide Emission and Grain Yield in Chinese Winter Wheat–Summer Maize Rotation: A Meta-Analysis

A systematic understanding of nitrous oxide (N2O) emission and grain yield in winter wheat–summer maize rotation, one of the most important cereal cropping systems in China, is still lacking. The primary aim of this study was to quantify the N2O emissions and grain yield, as well as responses to mitigation strategies, in this intensively managed agroecosystem. We conducted a pairwise meta-analysis by compiling a comprehensive dataset of annual N2O emissions (n = 530) and grain yields (n = 352) from peer−reviewed publications. The N2O emissions increased with nitrogen (N) fertilizer input rates following a linear model (r2 = 0.295, p < 0.001), giving a specific emission coefficient and background emission of 0.71% and 0.5 kg N ha−1 yr−1, respectively. The grain yields responded to the N input rates following a linear-plateau model (r2 = 0.478, p < 0.001), giving an optimal N input rate and maximum grain yield of 405 kg N ha−1 yr−1 and 15.5 t ha−1 yr−1, respectively. The meta-analyses revealed that reducing N fertilizers (approximately 50% of the full N input), water-saving irrigation, reduced or no tillage, and applying enhanced efficiency fertilizers significantly decreased N2O emissions (range: −45% to −9%) and increased or did not impact grain yields (range: −1% to 3%). We recommend that reducing agricultural inputs (i.e., N fertilizers, irrigation, and tillage) is a feasible N2O mitigation strategy in the intensively managed winter wheat–summer maize rotation that can be employed without additional environmental risks.

Diversity and Identification of Plant-Parasitic Nematodes in Wheat-Growing Ecosystems.

Several nematode species can be found in different densities in almost any soil ecosystem, and their diversity in those ecosystems depends on numerous reasons, such as climatic conditions and host presence. Cereals are one of the main hosts of plant-parasitic nematodes (PPN), chiefly root-lesion nematodes (RLN, Pratylenchus spp.) and cereal cyst nematodes (CCN, Heterodera spp.). These nematodes are known as major parasites of the cereal crops; however, agricultural areas accommodate various nematodes showing biological variation. The diversity of parasitic nematodes on cereals in the Sakarya provinces of Türkiye, where cereals are intensively grown and located in the middle of two climatic zones, has not been well studied. Therefore, in this study, we aimed to determine the diversity, identification, and molecular phylogeny of PPNs in wheat-growing ecosystems in the Hendek, Pamukova, Geyve, Akyazı, and Central districts of Sakarya. The diversity of PPNs was calculated using the Shannon diversity index. Thirteen PPN genera were detected in 92% of soil samples. Heterodera filipjevi was identified in 24% of the soil samples using morphological, morphometrical, and molecular tools. In the morphological and molecular analyses, intraspecific polymorphism was observed in H. filipjevi populations. The result indicated that the high infestation rate of H. filipjevi was recorded from Geyve and Pamukova, followed by Hendek and Akyazı; however, a low infestation rate was detected in the Central district. The moderate value of the Shannon index of migratory nematode species was obtained in wheat fields as 2.31, whereas the value of evenness was 0.93, implying moderate diversity and high evenness of nematodes. This study is the first comprehensive report on H. filipjevi from wheat cropping areas in the Sakarya province. Intensified cereal cropping systems with/without non-cereal rotations increased the risk of plant-parasitic nematodes, especially RLNs and H. filipjevi infection of wheat production areas in the province.

Diversified and Long-term Cropping Systems Alters the System Sustainability and Energy Use Efficiency in Soils of Indo-Gangetic Plains

The cereal-based intensive cropping practices have posed the yield at a plateau and reduced the energy use efficiency (EUE) of the cropping systems in the Indo-genetic plains (IGPs). The long-term cropping systems experimentations with 4 diversified legumes and cereal cropping systems and a grassland fallow system were studied for >10 years representing different agro-ecological regions at the agricultural research farm, IAS, BHU-Varanasi, Uttar Pradesh of IGPs to assess their impacts on system productivity and energy use efficiency. Out of 4 cropping systems viz, Pigeon pea-Pigeon pea (PP-PP) and Rice-Maize (R-M) systems were managed as conventional cultivation running under the breeding project, however; Dryland Rice-Lentil (R-L) and Zero-till Rice-Wheat (R-W) systems were running under agronomy project. The grassland fallow system was maintained in the agronomy block. The maximum system productivity was seen in the zero till rice-wheat (8185 kg ha-1) system and the lowestpigeon peanpea- pigeonpea system (1615 kg ha-1). However, the maximum EUE was found in pigeonpea system (13.23 MJ ha-1) and the lowest in the zero till rice-wheat system (8.88 MJ ha-1). The study suggests that the inclusion of legumes in the cropping system is vital in enhancing the system productivity and energy use efficiency than the long-term cereal-based system in long-run to the alluvial soils of IGPs.

Towards a Farmer-Centric Framework for Scaling Productive and Sustainable Cereal Cropping Systems

A case is made for an innovation system framework that integrates farmer-centric and systemic approaches to scaling plant nutrition innovations for positive transformation of cereal cropping systems in Sub-Saharan Africa. A case study from Ethiopia helps to build the case.

Continuous cropping legumes in semi-arid Southern Africa: Legume productivity and soil health implications

Abstract Legume agronomic research in Southern Africa has often focused on integrating legumes into smallholder cereal cropping systems, but there is limited information available on the feasibility and soil health implications of continuous cropping legumes in the region. Continuous legumes may be suitable in areas with large livestock populations where a premium is placed on high-quality forage, or where efforts are underway to reclaim degraded cropland. Our objectives in this study were to (i) evaluate the performance of diverse legumes under continuous cropping and conservation tillage management with no fertility inputs and (ii) assess the response of soil health parameters to continuous legumes in a semi-arid environment. A 4-year study was conducted in Limpopo, South Africa beginning in the 2011–2012 growing season in which 10 legume and fallow treatments were imposed in the same plots for 4 growing seasons. All legumes responded negatively in varying degrees to continuous cropping in terms of biomass and nutrient accumulation. Lablab (Lablab purpureus L.) was the top-performing legume in the study and accumulated 4.5–13 Mg ha−1 of biomass and 153–345, 11–34, and 75–286 kg ha−1 of N, P, and K, respectively. Lablab often outperformed natural fallow, while other legumes generally performed as well as or inferior to natural fallow, depending on species and growing season. Cowpea (Vigna unguiculata Walp) was especially incompatible with continuous cropping and averaged less than 252 kg ha−1 and 2.1 Mg ha−1 of grain and biomass, respectively, from 2012–2013 to 2014–2015. Continuous cropping did not lead to sustained improvements in soil health. By 2014–2015, soil organic matter for all treatments had either declined or resembled baseline values. Rates of potentially mineralizable N in cowpea, lablab, vining mucuna (Mucuna pruriens var. Utilis), natural fallow, and bare ground plots fell by 70–96% during the study. There was also evidence for lower recovery of leached K by legumes compared to natural fallow species. In conclusion, legumes, such as lablab, should be considered as continuous forages on marginal land in areas where high-quality forage is in demand, but continuous cropping legumes without fertility inputs are not an effective strategy for improving soil health on degraded cropland in this semi-arid region of Southern Africa. Future research efforts may focus on the grazing strategies and baling frequencies required to optimize annual biomass accumulation of continuous lablab to meet livestock demand and support smallholder livelihoods.

Diversifying cropping sequence reduces nitrogen leaching risks

• We monitored soil mineral N during various cropping sequences. • We simulated a 20-year series of N leaching for the cropping sequences. • We found an impact of the preceding cop on N leaching after the following crop. • Catch crop and oilseed rape volunteers reduced N leaching risk. • Diversified cropping sequences can reduce N leaching by up to 40 %. Overuse of chemical fertiliser in cereal cropping systems has resulted in severe degradation of air and water quality. Diversifying cropping sequence with legumes provides a natural source of nitrogen (N), but also increases N leaching risks after their growing period. Here, we hypothesize that legumes and other break crops, i.e., crops grown to diversify the cropping sequence, reduce N leaching at the rotation scale due to their contribution to increasing nutrient use efficiency and crop N recovery of the following cereal crops. In two 4-year experiments conducted in northern France, we monitored agronomic performance and the changes in the soil mineral N content at field scale in six preceding crop-current crop combinations including winter wheat ( Triticum aestivum ), pea ( Pisum sativum L.) and oilseed rape ( Brassica napus L.). We quantified N leaching after each crop as a function of the preceding crop with a water-fluxes model based on soil mineral N content, climate data and soil characteristics. We then simulated N leaching at the rotation scale, for 20 years of climate conditions and various cropping management systems. We show that growing pea or oilseed rape reduced soil mineral N content at harvest of the following cereals (up to mean values of −28 and −19 kg N ha −1 respectively), and N leaching risks during winter of the following cereals compared to the wheat-wheat cropping sequence. Although N leaching was higher during the winter after pea was cultivated, the cumulative losses over four experimental years of the pea cropping sequences were not significantly higher than the no-break cropping sequences. Over the 20 climate years, sequences including pea, oilseed rape, volunteers or catch crops reduced simulated N leaching by up to 40 % compared to wheat monoculture. Our study confirms that N leaching not only depends on the current crop but is also affected by the preceding crop. A large potential reduction in nitrogen leaching could be achieved in many intensive cereal-growing regions with very limited cropping sequence diversity.

Biomass Quantity and Quality from Different Year-Round Cereal–Legume Cropping Systems as Forage or Fodder for Livestock

The quantity and quality of forage and fodder crops is the major drawback of the livestock sector in the country. There is a need to bridge the gap between the supply and demand of fodder through the adoption of specific sustainable fodder production strategies. The field experiments were conducted during kharif (rainy, June–October), rabi (post-rainy, October–February), and summer (March–May) seasons of 2018–19 and 2019–20 to identify a sustainable fodder cropping system module in randomized complete block design with fifteen fodder cropping systems in three replications. The main objective of this research was to identify the most productive cereal–legume cropping system, both in terms of quantity and quality of biomass, to reduce the gap between supply and demand of quality livestock feed around the year. Among cropping systems, Bajra–Napier hybrid intercropped with lucerne, cowpea, and sesbania recorded significantly higher green fodder (163.6, 155.2, and 144.0 t/ha/year, respectively) and dry matter yields (32.1, 30.8, and 31.3 t/ha/year, respectively). Similarly, the same perennial systems also recorded higher quality yield and ash content. However, higher crude protein content was noticed in monocrop legumes, with the highest in sesbania (22.32%), while higher ether extractable fat was found in monocrop sesbania (3.78%). The monocrop oats recorded higher non-fiber carbohydrates (36.90%) while a monocrop of pearl millet recorded higher total carbohydrates (80.75%), however they were on par with other monocrop cereal cropping systems. Cultivation of legumes as a monocrop, and their inclusion as an intercrop with cereals resulted in lower fiber fractions and improved crude protein in intercropping systems. Furthermore, this improved the dry matter intake and digestibility of fodder. With higher sustainable yield index values and land-use efficiency, perennial intercropping systems were also found to be sustainable. Thus, cultivation of the Bajra–Napier hybrid with either lucerne, cowpea, or sesbania as an intercrop will help livestock farmers to achieve higher productivity in terms of quantity and quality, and forms a viable option for overcoming livestock feed scarcity.