Continuous Maize System Research Articles

Carbon stock, aggregate stability and hydraulic properties of soils under tillage, crop rotation and mineral fertiliser application in sub-humid Zimbabwe

Appropriate tillage and crop diversifications can improve soil quality leading to yield sustainability. Our objective was to quantify tillage, crop rotation and mineral fertiliser application effects on carbon sequestration, aggregation and soil water movement after two cropping cycles in the smallholder sector of Zimbabwe. Two split-plot experiments were set up at four sites on sandy, loamy and clayey soils. At experiment 1, crop rotation (maize-soya bean; continuous maize) was the main plot and mineral fertiliser ((NPKS (180 N + 30P2O5+30K2O+6.5SO3 kg ha−1); control (no fertiliser added)) was the sub-plot. At experiment 2, tillage (reduced, conventional) was the main plot and mineral fertiliser (NPKS; control) was the sub-plot. Soil samples collected from 0 to 0.2 m and 0.2–0.4 m layers were analysed for soil organic matter (SOM) content, bulk density and proportion of water stable aggregates. Saturated hydraulic conductivities (Ks), steady state infiltration rates (is) and soil sorptivities (Sp) were estimated from fitting field infiltration data into the Phillip model. SOM stocks (mean = 3.483 Mg ha−1) were significantly increased by reduced tillage at the sandy site and higher (p < 0.05) in 0–0.20 m than in 0.20–0.40 m layers at clayey sites. Proportion of water stable aggregates increased (p < 0.05) under reduced tillage compared with conventional tillage and under rotation compared with continuous maize system. Bulk densities were 11% lower (p < 0.05) in the 0–0.20 m than in 0.20–0.40 m layers. The estimated Ks(1 × 10−4-8x10−4 cm s−1) and is (7.08–55 × 10−4 cm s−1) were at least 100% higher (p < 0.05) under rotation compared with continuous maize whilst sorptivities (0.050–0.143 cm s−05) did not vary across the treatments. NPKS fertiliser reduced (p < 0.05) is by up to 1.8 fold compared with the control. Short term adoption of reduced tillage and maize-soya bean rotation can mitigate soil structural degradation; increase water recharging and increase carbon sequestration quicker in sands than in the buffering clays making the practices more relevant in the smallholder sector.

Maize diversification and nitrogen fertilization effects on soil nitrous oxide emissions in irrigated mediterranean conditions

Maize is a major irrigated crop in Mediterranean areas and its typical intensive management may impact soil nitrous oxide (N2O) emissions. In these irrigated continuous maize systems, the legumes incorporation as well as adjusted nitrogen (N) fertilization might be interesting strategies to reduce soil N2O emissions. The objective of this study was to assess the impact of cropping diversification and different N rates on soil N2O emissions in flooded irrigated maize under Mediterranean conditions. To achieve this, two cropping systems (maize monoculture system, MC; and pea -maize rotation, MP) and 3N rates (unfertilized, 0N; medium rate, MN; and high rate, HN) were evaluated in a field experiment established in NE Spain during 2 years (2019; 2020). During the studied period, the N rate had a significant effect on soil N2O emissions, with a non-linear positive response of cumulative soil N2O emissions to N rates. In both systems, quick and high increases of soil N2O fluxes were observed immediately after the N application reaching 55 and 100 mg N2O-N m−2 day−1 in MC and MP, respectively. Both years, the pea phase of the MP rotation showed greater cumulative N2O emissions than the fallow of MC. However, N2O losses in the maize phase were similar (2019) or even higher (2020) in MC than in MP. Moreover, in both seasons, the MN treatments showed lower yield-scaled N2O emissions and N emission factor than the HN treatments, being this last lower than 1% in all cases. The results obtained showed that in irrigated Mediterranean conditions the replacement of a fallow by a legume, together with an adjusted N fertilization are favourable strategies to mitigate soil N2O emissions in high-yielding maize systems.

Stover management modifies soil organic carbon dynamics in the short-term under semiarid continuous maize

In croplands, the adoption of certain management practices may increase soil organic carbon (SOC) levels. In this study, we evaluated the short-term impact of crop stover management and the interaction between crop stover and irrigation method on SOC change in a continuous maize (Zea mays L.) system in Spain. Four years after the beginning of the experiment, total SOC and C fractions (particulate organic matter carbon, POM-C; and mineral-associated organic matter carbon, Min-C) contents, SOC stocks and SOC stock changes were measured in four different soil layers (0−5, 5−10, 10−25 and 25−50 cm) in an experiment with two irrigation methods (sprinkler and flood) and three stover management systems (conventional tillage with all the stover incorporated, CT; no-tillage maintaining the stover, NTr; and no-tillage removing the stover, NT). Stover management resulted in significant differences in SOC and POM-C but not in Min-C. In particular, NT reduced SOC and POM-C contents compared with CT and NTr (about 10 and 60 %, respectively). After 4 years, SOC change was not affected by the interaction between stover management and irrigation. Concurrently, both CT and NT showed SOC losses, reaching 0.11 and 1.22 Mg ha−1 yr−1 in CT and NT, respectively. However, NTr showed SOC gains at a rate of 0.09 Mg ha−1 yr−1. Consequently, the removal of crop stover has been demonstrated as a detrimental strategy to store SOC in the short-term in irrigated continuous maize systems.

The impact of cropping system, tillage and season on shaping soil fungal community in a long-term field trial

Our understanding of seasonal dynamics of fungal communities under different agricultural management practices remains limited. In this study, phospholipid fatty acid (PLFA) analysis and Illumina MiSeq high-throughput sequencing targeting fungal ITS1 region were combined to assess the responses of soil fungal communities to different tillage practices and cropping systems during the crop growing season. Bulk soils were collected from two long-term tillage practices (conventional tillage, CT and no-tillage, NT) under two cropping systems (maize (Zea mays L.)-soybean (Glycine max Merr.) rotation and continuous maize) in April, June and August of 2015 at 0–5 cm and 5–15 cm depths. Our results clearly highlighted the importance of cropping system and tillage for soil fungi; seasonal effect, by contrast, was weaker. The fungal PLFA content, used as an indicator of fungal biomass, appeared higher under continuous maize system than maize-soybean rotation system at depths of 0–5 cm and 5–15 cm, and higher in NT than CT at 0–5 cm depth, irrespective of sampling time. DNA-based sequencing results showed that soil fungal diversity (i.e. Shannon) and evenness (i.e. Pielou) indices were higher under rotation cropping system than continuous maize system at both soil depths. Soil fungal richness (i.e. Chao1) index was higher in NT than in CT at 0–5 cm depth. None of these three α diversity indices were significantly affected by sampling time. Cropping system and tillage played the most important roles in shaping soil fungal community at both soil depths. At 0–5 cm depth, there was an obvious consistent trend of enrichment from Ascomycota in maize-soybean rotation system to Basidiomycota in continuous maize system over the growing season. At 5–15 cm depth, there was an obvious consistent trend of enrichment from Tausonia and Chaetomidium in CT to Leptodontidium, Ceratobasidium in NT over the crop growing season. Notably NT favored symbiotrophs throughout the growing season, irrespective of cropping system and soil depth.

Assessing synergistic effects of no-tillage and cover crops on soil carbon dynamics in a long-term maize cropping system under climate change

Climate-smart agriculture management practices such as no-tillage (NT) and cover crops (CCs) have been widely applied and are expected to offer multiple environmental benefits (e.g., soil carbon sequestration, yield stability, and climate resilience). However, the long-term effects of these management practices, especially their synergistic interaction, have not been well addressed. This study used an improved agroecosystem model (DLEM-Ag) to explore the synergistic effects of NT and CCs on soil carbon dynamics in a continuous maize system in the middle south of the United States for 1970–2099. Simulation results for 1970–2018 show that NT, relative to conventional tillage (CT), led to carbon gains (0.22 Mg C ha−1 yr−1) in the topsoil in a CC-inclusive continuing maize system; however, NT per se brought minor net carbon gains. This well captures the field observations. Model factorial analyses reveal that soil carbon sequestration was highly correlated with biomass carbon inputs from both the winter cereal CC and the summer maize. Elevated CO2 and warming effects were the main contributors to soil carbon gains, as these promote CC growth. Further model projections suggest that soil organic carbon would increase in the RCP 8.5 future scenarios (2019–2099), with greater gains under NT-CCs than under CT-CCs (0.089 vs. 0.058 Mg C ha−1 yr−1), largely due to enhanced CC biomass production. Moreover, NT-CCs would reduce carbon loss compared to CT-CCs (-0.002 vs. -0.017 Mg C ha−1 yr−1) in the RCP 2.6 scenarios. Our study highlights the importance of CCs in enhancing cropland carbon sequestration and indicates that NT and CCs, taken together, can serve as a viable strategy to ensure crop production through promoting soil health in similar maize cropping systems.

Modeling crop yield and nitrogen use efficiency in wheat and maize production systems under future climate change

In the face of global climate change, changes in nitrogen use efficiency (NUE) have not been widely considered to affect agricultural productivity. A modeling study was conducted to assess the impacts of future climates on crop yields and NUE in two wheat (Triticum aestivum L.) and maize (Zea mays L.) rotation systems and one continuous maize system in northern China. Specifically, the process-based SPACSYS model was used to predict crop yields and NUE by 2100, under four climate scenarios (Baseline, RCP2.6, RCP4.5 and RCP8.5). The model was validated using data from three long-term experiments, each of which included four fertilization practices typical of the regions: non-fertilizer, combined mineral N, phosphorus (P) and potassium (K) (NPK), NPK plus manure and NPK plus straw. Validation showed SPACSYS well-simulated crop yields and N uptake (R2: 0.41–0.96; RMSE: 6–18%; and EF: 0.41–0.93). Under future climate change, the model predicted changes in maize yield by − 30.69% and 5.98% in northwestern and northeastern China, respectively, and wheat yield by − 16.37% in northwestern China. Future climates would cause greater NUE reductions in the northwest (wheat: 42.79%; maize: 33.73%) than in the northeast (maize: 3.97%) with smaller decreases in crop N uptake and N loss. Furthermore, manure application had higher crop NUEs (wheat: 6.66–31.27%; maize: 23.82–68.19%) and N uptakes than other treatments under future climate change. The results demonstrated the risks of future climate changes on crop yield and NUE in the study regions and can also help target fertilization practices for effectively mitigating climate change.

Maximum soil organic carbon storage in Midwest U.S. cropping systems when crops are optimally nitrogen-fertilized

Nitrogen fertilization is critical to optimize short-term crop yield, but its long-term effect on soil organic C (SOC) is uncertain. Here, we clarify the impact of N fertilization on SOC in typical maize-based (Zea mays L.) Midwest U.S. cropping systems by accounting for site-to-site variability in maize yield response to N fertilization. Within continuous maize and maize-soybean [Glycine max (L.) Merr.] systems at four Iowa locations, we evaluated changes in surface SOC over 14 to 16 years across a range of N fertilizer rates empirically determined to be insufficient, optimum, or excessive for maximum maize yield. Soil organic C balances were negative where no N was applied but neutral (maize-soybean) or positive (continuous maize) at the agronomic optimum N rate (AONR). For continuous maize, the rate of SOC storage increased with increasing N rate, reaching a maximum at the AONR and decreasing above the AONR. Greater SOC storage in the optimally fertilized continuous maize system than in the optimally fertilized maize-soybean system was attributed to greater crop residue production and greater SOC storage efficiency in the continuous maize system. Mean annual crop residue production at the AONR was 22% greater in the continuous maize system than in the maize-soybean system and the rate of SOC storage per unit residue C input was 58% greater in the monocrop system. Our results demonstrate that agronomic optimum N fertilization is critical to maintain or increase SOC of Midwest U.S. cropland.

Fallow associated with autumn-plough favors structure stability and storage of soil organic carbon compared to continuous maize cropping in Mollisols

Aggregate formation and stability of soil organic carbon (SOC) differ in different farming systems, probably due to differences in effects of tillage and residue management. This study used a 24-year field experiment to compare the effects of continuous maize cropping and natural fallow on aggregate formation and SOC storage in various aggregate-size classes and density fractions of a Chinese Mollisol. Soils collected from the upper 0.2-m layer were wet-sieved into four aggregate-size classes (>2, 0.25–2, 0.053–0.25 and 0.25 mm) and increased that of micro-aggregates (<0.25 mm) compared to the initial value while the opposite was observed in the natural fallow system. The fallow system generally had greater SOC concentration in the occluded fraction, higher proportion of newly-derived C as % total SOC in the light fraction and greater contribution of total residue C to new C in macro-aggregates and light fractions compared to the continuous maize system. Furthermore, the fallow system resulted in shorter turnover time of SOC than the continuous maize system. Natural fallow associated with autumn-plough improved soil structural stability and SOC storage while continuous maize cropping with residue removal decreased SOC sequestration and soil aggregate stability.

Effect of different fertilization managements on nitrate accumulation in a Mollisol of Northeast China

In a continuous spring maize system in Northeast China, the accumulation and succession characteristics of nitrate in Mollisol with four fertilization treatments, including no fertilization (CK), farmers’ conventional fertilization (FC), recommendation fertilization (RF), and controlled release fertilizer application (CRF), were compared over a 6-year field plot trial. On average, the RF and CRF treatments decreased nitrate nitrogen by 16.6 and 39.5 % in the 0–90 cm soil layer, respectively, and maintained a relatively high maize grain yield, as compared to the FC treatment. The accumulation of nitrate nitrogen was more obvious in the CRF treatment compared with the other fertilizer treatments under the arid climate. However, the high precipitation resulted in the leaching of nitrate nitrogen into the deeper soil layer in all the fertilizer treatments. The maximum of nitrate nitrogen in the 0–90 cm soil layer was 81.4 kg N/ha at a nitrogen fertilizer rate of 250 kg N/ha in the long-term trial, which was within the rational and safe level for groundwater. The best fertilization strategy to decrease nitrate accumulation in soil should consider both soil characteristics and precipitation.

The Variation of Nitrate in the Soil Profile for Continuous Spring Maize System under Different Soil Fertilities in the Northeast of China

In the continuous Spring Maize system in Northeast China,the nitrate accumulation and succession characteristics of different soils and fertility in three locations with five fertilization treatments, which included no fertilizer treatment (CK), farmer conventional treatment (FC), recommendation fertilization (RF), control-released fertilizer (CRF) and single fertilization (SF), was compared by 6 years’ long-term experiment. The results showed that nitrate accumulation was drastically significant in high pH soils; potential nitrate increasing trend of high fertility soil was lower; new type fertilizer, for example controlled release fertilizer (CRF), and recommendation fertilizer rate (RF) could obviously decrease nitrate accumulation in single fertilization and in split fertilization; the nitrate excessive accumulation in soils could be improved by not only controlling fertilization, fertilizer and fertilizer rate, but also considering of soil types and soil fertility; and at present, in Northeast China, nitrate accumulation was in rational and safety level, but still exist potential risk.

Comparison of Cellulosic Ethanol Yields from Midwestern Maize and Reconstructed Tallgrass Prairie Systems Managed for Bioenergy

Maize- and prairie-based systems were investigated as cellulosic feedstocks by conducting a 9 ha side-by-side comparison on fertile soils in the Midwestern United States. Maize was grown continuously with adequate fertilization over years both with and without a winter rye cover crop, and the 31-species reconstructed prairie was grown with and without spring nitrogen fertilization. Both maize stover and prairie biomass were harvested in the fall. We compared amounts of cellulosic biomass produced and harvested, carbohydrate contents as measured by both dietary and detergent methods, and estimated cellulosic ethanol yields per hectare. From 2009–2013, the cropping system with the largest non-grain biomass yield was fertilized prairie, averaging 10.4 Mg ha−1 year−1 aboveground biomass with average harvest removals of 7.8 Mg ha−1 year−1. The unfertilized prairie produced 7.4 Mg ha−1 year−1 aboveground biomass, with average harvests of 5.3 Mg ha−1 year−1. Lowest cellulosic (non-grain) biomass harvests were obtained from continuous maize systems, averaging 3.5 Mg ha−1 year−1 when grown with, and 3.7 Mg ha−1 year−1 when grown without a winter rye cover crop, respectively. Unfertilized prairie biomass and maize stover had equivalent dietary-determined potential biomass ethanol yields at 330 g ethanol kg−1 dry biomass, but fertilized prairie was lower at 315. The detergent method did not accurately capture these differences. Over the five-year period of the experiment, unfertilized and fertilized prairie systems averaged 810 and 1,790 L potential cellulosic ethanol ha−1 year−1 more than the maize systems, respectively. Differences in harvested biomass accounted for >90 % of ethanol yield variation.

Assessment of the Profitability and the Effects of Three Maize-Based Cropping Systems on Soil Health in Western Africa

Enhanced livelihoods for populations, especially smallholder farmers in sub-Saharan Africa may be achieved through improved cropping systems. We assessed the economic returns from maize grain yield and the effects of three cropping systems on soil properties in an eight-year study segmented in cycles of two years each: continuous maize (Zea mays L.), maize-mucuna (Mucuna pruriens var. utilis), and maize-pigeon pea (Cajanus cajan). The rainfall pattern in the study region allows for two growing seasons per year, leading to four growing seasons per cycle. Nitrogen (N) and phosphorus (P) fertilizer rates were imposed on maize in each system and maize grain yields and associated cash values as well as soil properties were measured. Seeding mucuna and pigeon pea crops into maize crop in the first year did not result in maize grain yield increases from N and P fertilizers in the subsequent year. Continuous maize system increased mean maize grain yields by 6.2 to 60.3% in the fallow year of the 2002-2003 and 2006-2007 cycles and by 5.1 to 8.2% on a cycle basis in the 2002-2003 cycles. For the remaining periods of the study, mucuna and pigeon pea based maize cropping increased grain yields by 28.6 to 47.6%, 22 to 260% and 28.3 to 136.1% in fallow year, non-fallow years and on a cycle basis, respectively, compared to yields under continuous maize. On a cycle basis, economic returns for maize-mucuna and maize-pigeon pea based systems were 105.1 and 66.5%, respectively, higher than that for continuous maize. The mucuna and pigeon pea based systems increased the initial soil total carbon (C) content by 55 and 69%, respectively, resulted in increases of 110 to117%, 33 to 63%, 29%, and 16-17% for exchangeable Ca2+, Mg2+, K+ and total cation exchange capacity (CEC), respectively, and enhanced water stable macroaggregates stability, compared to continuous maize. Maize mucuna and pigeon pea-based maize cropping systems with mucuna and pigeon crops in alternate years should be advised towards sustaining enhanced profitability and improved soil physical and chemical properties.

Phosphorus agronomic efficiency in maize-based cropping systems: A focus on western Kenya

Phosphorus (P) is facing a quantity and quality supply issue and increasing its use efficiency is important for its continued use and profitability in crop production. The objective of this study was to determine how agronomic efficiency of P (PAE) in different environments and management systems in western Kenya is affected by N application, inherent soil fertility and organic resources. We used data constituting over 2700 data points from 126 farm fields of 25 different studies conducted from 1996 to 2009. Potassium (K) deficiency is negligible in western Kenya while ommission of P and N result in a 50% and 43% reduction in yield, respectively, relative to a full NPK treatment. In poor fields (low control yields) PAE was low in the absence of fertilizer N. Overall, lack of N application decreased PAE from 29 to 19kg grain kg−1P. Boundary analysis indicate that maximum yields are reached at about 50kgPha−1. Using a marginal rate of return of 100%, maximum P application rate for western Kenya should be 38kgPha−1. Without chemical N fertilizer application, organic resources increased PAE by 60–100% compared to continuous maize system without organic resources. Maximum PAE decreased at increased plant-available soil P and soil coarsiness. Our analysis represents best management practices and PAE may be lower than the reported values under farmer's conditions.

English

Inland valleys are being used under the Sawah technology for rice production to reduce rice imports to Ghana. Sawah technology is assumed to benefit from geological fertilization. However, there is no quantitative information on runoff and sediment flows in the agricultural watershed of Ghana. This study was carried out at Biemso in the southern part of the country. The aim was to estimate runoff and sediment transport using the water erosion prediction project (WEPP) model (version 2006.500), from hillslope to the valley bottom where rice is cultivated using the&nbsp;Sawah technology. A digital elevation model (DEM) was created from ground survey and used to select the various plots (hillslopes) and to select slope input parameters. Four plots (hillslopes) were selected for the model simulation. Data on local daily values of rainfall and on minimum and maximum temperatures were used to set a CLIGEN model station file to determine climate input parameters for the model. Rainfall characteristics (erosivity and distribution) were analysed. Soil erodibility was also determined. Soil and crop management input parameters required by the model were identified and or estimated from field measurements and secondary sources. The model was run for two management scenarios: Fallow and continuous maize systems. The results of the simulation showed that 2.9 to 3.9 and 6.8 to 10.2 t/ha/year of sediments were eroded from upper catchment to valley bottom under fallow system and maize, respectively.&nbsp;The range of values for&nbsp;runoff produced under fallow was 17.4 to 40 mm whereas that under maize system is 158.7 to 233.62 mm. The study has shown that land use system in the study area has a great influence on geological fertilization. In addition, the valley bottom where rice is produced under the Sawah system is enriched with organic matter from upslope. &nbsp; Key words:&nbsp;Geological fertilization, sediment,&nbsp;sawah, inland valleys, runoff, water erosion prediction project (WEPP) (2006.500) model.

Sustainability of European maize-based cropping systems: Economic, environmental and social assessment of current and proposed innovative IPM-based systems

There is strong social and political pressure to reduce pesticide use in European agriculture. Evaluating the sustainability of cropping systems is a complex task due to the conflicting objectives underlying its economic, social and environmental dimensions. Multi-criteria assessment of different Integrated Pest Management (IPM) scenarios and evaluation of the most sustainable options at regional, national and European level is essential. Within the EU Network of Excellence ENDURE, two expert-based surveys were conducted (i.e. interviews), where experts from four European regions (northern region, Denmark and The Netherlands; central-eastern, Tolna and Békés counties in Hungary; south-western, Ebro Valley in Spain; southern, Po Valley in Italy) determined which are the main current maize-based cropping systems (MBCSs) in their region and proposed innovative IPM-based systems. The DEXiPM® (DEXi Pest Management) model for arable cropping systems was used to evaluate and compare the economic and environmental sustainability of these systems. The social sustainability was evaluated by adapting indicators of this model to the specificities of maize systems. The assessments showed that all innovative rotated MBCSs proposed in the four regions can have a higher environmental sustainability than and maintain the same economic sustainability as current rotated systems. These cropping systems are thus acceptable for testing under “real” field conditions. Only the innovative continuous maize system proposed in the central-eastern region was both economically and environmentally more sustainable than the current system. All innovative systems had a positive impact on work safety but according to local expert opinion producers and consumers are not ready to implement them or to accept their higher-priced products, with the exception of consumers in the northern region. These results suggest the need for European and regional policies to encourage the adoption of innovative rotated MBCSs that have positive agronomic and environmental impact through IPM implementation. The major constraints that inhibit this adoption were predominantly relating to (1) the lack of access that farmers have to the practical knowledge needed to effectively manage these systems and (2) the insufficient consumer awareness and acceptance of product improvements associated with IPM. To overcome these constraints supportive policy environments, well-functioning knowledge management systems (including good farmer support networks) and effective marketing is required.

Soil microbial biomass and mineralization of aggregate protected carbon in fallow-maize systems under conventional and no-tillage in Central Zimbabwe

Abstract Soil organic carbon has been reported to increase soil microbial activities in soils. However, very few studies have evaluated soil microbial biomass carbon (SMBC), aggregate protected carbon, and mineralizable carbon, SOC associated with sand, silt and clay and aggregate stability under fallow-maize rotation systems. The objectives of this study were to determine SMBC, aggregate protected carbon, and mineralizable carbon, SOC associated with sand, silt and clay and aggregate stability under conventional tillage (CT) and no-tillage (NT) in a fallow-maize rotation system. We hypothesized that improved fallow systems, which are fast growing leguminous trees grown during the fallow phase, had greater SMBC, aggregate protected carbon, SOC in the different soil fractions and aggregation when compared to natural fallow or continuous maize systems. Treatments studied were improved fallows of Acacia angustissima (A. Angustissima), Sesbania sesban (S. Sesbania), natural fallow and continuous maize. Samples were collected from 0–50, 50–100 and 100–200 mm depths 1 year after fallow termination in plots subjected to CT and NT. Total SOC was determined by wet combustion, SMBC by fumigation extraction, aggregate protected SOC by wet sieving and sedimentation into sand, silt and clay after 21-day incubations of intact and crushed macroaggregates of size

Soil organic carbon dynamics of improved fallow-maize rotation systems under conventional and no-tillage in Central Zimbabwe

Fallowing increases soil organic carbon (SOC) during the fallowing phase. However, this benefit is lost quickly during the cropping phase. The objective of this study was to evaluate SOC dynamics of an improved fallow-maize rotation under no-tillage (NT) and conventional tillage (CT) from time of fallow termination, through the next two cropping seasons. The treatments studied were improved fallows of Acacia angustissima (A. angustissima) and Sesbania sesban (S. sesban), natural fallow and continuous maize. Our hypothesis is that fallowing maintained higher SOC and lower soil bulk densities through the cropping phase when compared with continuous maize system and that NT maintained higher SOC when compared with CT. Soil organic carbon was significantly greater under fallows than under continuous maize from fallow termination to the end of the second cropping season. Soil organic carbon for the 0–5 cm depths was 11.0, 10.0, 9.4 and 6.6 g kg−1 for A. angustissima, S. sesban, natural fallow and continuous maize, respectively at fallow termination. After two cropping seasons SOC for the same depth was 8.0, 7.0, 6.1, 5.9 g kg−1 under CT and 9.1, 9.0, 8.0, 6.0 g kg−1 under NT for A. angustissima, S. sesban, natural fallow and continuous maize, respectively. Total SOC stocks were also higher under fallows when compared with continuous maize at fallow termination and after two cropping seasons. Soil bulk densities were lower under fallows when compared with continuous maize during the period of study. We concluded that fallows maintained greater SOC and NT sequestered more SOC than CT. Acacia angustissima was the better tree legume fallow for SOC sequestration when compared with S. sesban or natural fallow because it maintained higher SOC and lower bulk densities after two seasons of maize cropping.

Soil greenhouse gas fluxes and global warming potential in four high‐yielding maize systems

AbstractCrop intensification is often thought to increase greenhouse gas (GHG) emissions, but studies in which crop management is optimized to exploit crop yield potential are rare. We conducted a field study in eastern Nebraska, USA to quantify GHG emissions, changes in soil organic carbon (SOC) and the net global warming potential (GWP) in four irrigated systems: continuous maize with recommended best management practices (CC‐rec) or intensive management (CC‐int) and maize–soybean rotation with recommended (CS‐rec) or intensive management (CS‐int). Grain yields of maize and soybean were generally within 80–100% of the estimated site yield potential. Large soil surface carbon dioxide (CO2) fluxes were mostly associated with rapid crop growth, high temperature and high soil water content. Within each crop rotation, soil CO2 efflux under intensive management was not consistently higher than with recommended management. Owing to differences in residue inputs, SOC increased in the two continuous maize systems, but decreased in CS‐rec or remained unchanged in CS‐int. N2O emission peaks were mainly associated with high temperature and high soil water content resulting from rainfall or irrigation events, but less clearly related to soil NO3‐N levels. N2O fluxes in intensively managed systems were only occasionally greater than those measured in the CC‐rec and CS‐rec systems. Fertilizer‐induced N2O emissions ranged from 1.9% to 3.5% in 2003, from 0.8% to 1.5% in 2004 and from 0.4% to 0.5% in 2005, with no consistent differences among the four systems. All four cropping systems where net sources of GHG. However, due to increased soil C sequestration continuous maize systems had lower GWP than maize–soybean systems and intensive management did not cause a significant increase in GWP. Converting maize grain to ethanol in the two continuous maize systems resulted in a net reduction in life cycle GHG emissions of maize ethanol relative to petrol‐based gasoline by 33–38%. Our study provided evidence that net GHG emissions from agricultural systems can be kept low when management is optimized toward better exploitation of the yield potential. Major components for this included (i) choosing the right combination of adopted varieties, planting date and plant population to maximize crop biomass productivity, (ii) tactical water and nitrogen (N) management decisions that contributed to high N use efficiency and avoided extreme N2O emissions, and (iii) a deep tillage and residue management approach that favored the build‐up of soil organic matter from large amounts of crop residues returned.

Cover Cropping and Nutrient Management Strategies for Maize Production in Western Africa

Introduction of cover cropping systems may be important to a stable food supply in sub‐Saharan Africa. We examined the effects of three cropping systems in a 2‐yr, four growing season study in Togo: continuous maize (Zea mays L.), maize–mucuna [Mucuna pruriens (L.) D.C.], and maize–pigeon pea (Cajanus cajan L.). Mucuna and pigeon pea were grown in 1‐ or 2‐yr cycles, and three N and two P fertilizer rates were factorially applied on maize. Use of mucuna and pigeon pea after maize in the first year reduced N and P fertilizer needs in the subsequent year. Cover crops increased maize grain yield by 37.5 and 32.1%, respectively, in the second year. Two‐year cumulative economic returns on maize production were optimal when cover crops were grown every other year (every fourth season), compared to continuous maize or annual cover crops. The April 2002 to December 2003 soil N budgets showed a gain of N (&gt;400 kg ha−1) under all cropping systems. Initial soil nitrate (NO3)–N was reduced by 57.8% under the continuous maize system, but increased by 39 and 3.6% under the mucuna‐based and pigeon pea–based systems, respectively. Low (&lt;20 kg ha−1) N losses occurred during the fallow period. Phosphorus losses occurred for all periods, but a mucuna‐based cropping system has potential for soil P replenishment. The relay of a mucuna cover crop into maize in one out of 2 yr was most economical and improved soil N and P status without commercial fertilizers.

Effects of grain legumes and cover crops on maize yield and plant damage by Busseola fusca (Fuller) (Lepidoptera: Noctuidae) in the humid forest of southern Cameroon

Abstract Field trials were run in the humid forest zone of Cameroon to investigate the effects of crop rotation, cover crops and bush fallow on infestations by the noctuid stemborer Busseola fusca (Fuller) and on yield of maize. A continuous maize production system was compared with crop sequence systems, in which maize followed a grain legume (cowpea, soybean), cover crop (mucuna, pigeon pea) or a bush fallow. Compared to the continuous maize cropping system, maize in the crop sequence with legume and fallow systems had significantly higher leaf and stem nitrogen content at 35 and 63 days after planting (DAP), respectively. Differences in K and P at 35 and 63 DAP, and of N in stem and grain at harvest were not significant. Maize in the rotation systems had 1.5–2 times more borers per plant compared to the continuous maize production systems, particularly at the early stages of maize growth. At 63 DAP, larval mortalities were 1.4–1.5 higher in rotation systems than in the continuous maize system. As a result, dead-hearts and tunnel length did not vary significantly among treatments. In the insecticide protected plots, when comparing with the maize–maize cropping system, average grain yields were increased by 15.1–24.6% and 30.3–42.5% in crop sequences of grain legumes with maize and cover crops fallow systems, respectively. However, grain yield losses due to borers were 1.9–3.1 times higher in the continuous maize production system than in the crop sequences of grain legumes with maize and 4.5–11.1 times higher compared to maize after cover crops. It is concluded that an increased nutritional status of the plants lead to an increase in borer attacks at the early stage of plant growth, but also to improved plant vigour, resulting finally in a net benefit for the plant and grain yield.