1,721,172 research outputs found
Crop modelling based analysis of site-specific production limitations of winter oilseed rape in northern Germany
Full text linkWinter oilseed rape production is typically characterised by low nitrogen (N) use efficiency. Defining site-specific fertiliser strategies based on field trials and crop modelling may help to improve the ecological efficiency of this crop. However, no model has been evaluated for winter oilseed rape that simulates the growth of the plant as limited by the interaction of water and N. In this study, the APSIM canola model which was originally developed for the temperate regions of Australia, was adapted for conditions in Germany and tested against measured data (total biomass, grain yield, leaf area index, N-uptake and soil mineral N) at three sites near Göttingen (northern Germany). In the second part of the study, the evaluated model was used in a simulation experiment to explore site-specific climate and soil related production limitations to match fertiliser rates to yield targets. Historical weather data from four sites across northern Germany and a fertile loamy soil with different rooting depths, implicating different plant available water capacities, were used. Model results showed large differences in yield (up to 1000 kg ha−1) and N-balance (>30 kg ha−1) for 200 kg N-fertiliser rate ha−1 between restricted (50 cm) and unrestricted rooting depths. Simulated yields for such high N-fertiliser rate were lower for sites with continental climate than for sites close to the coast, reflecting different rainfall patterns. Results indicate that water supply plays a critical role when maintaining high N use efficiency and reaching simultaneously grain yields of 4000 kg ha−1
Exploring short-term ley legumes in subtropical grain systems: Production, water-use, water-use efficiency and economics of tropical and temperate options
Full text linkBiomass production, soil water extraction, and water-use efficiency (WUE, kg dry matter (DM)/ha.mm growing-season water use) of tropical, summer-growing and temperate, winter-growing forage legumes suited to short-term rotations with crops were compared over several growing seasons in southern Queensland. Tropical legumes lablab (Lablab purpureus cvv. Highworth and Endurance), burgundy bean (Macroptillium bracteatum cvv. Cardarga/Juanita mix), and butterfly pea (Clitoria ternatea cv. Milgara) were compared with forage sorghum (Sorghum spp. cv. Silk and cv. Sugargraze). Temperate legumes snail medic (Medicago scutellata cv. Sava), lucerne (Medicago sativa cv. UQL-1), sulla (Hedysarum coronarium cv. Wilpena), and purple vetch (Vicia benghalensis cv. Popany) were compared with forage oats (Avena sativa cv. Taipan/Genie). Production and WUE of winter legumes was highly variable, with oats producing more biomass than the legumes, except in 2009 where oat establishment was poor. In years with good establishment, WUE of oats (14–28 kg DM/ha.mm), snail medic (13–25 kg DM/ha.mm), and sulla (12–20 kg DM/ha.mm) were similar, but the production and WUE of vetch were generally lower (6–14 kg DM/ha.mm). Sulla dried the soil profile by 60–100 mm more than the annual species, but less than lucerne. Summer legumes, burgundy bean, and lablab performed similarly, although always produced less biomass and had lower WUE than forage sorghum. Lucerne extracted more water and maintained a drier profile by 70–150 mm and had lower WUE (<10 kg DM/ha.mm) than burgundy bean or lablab (9–30 kg DM/ha.mm). Of the legumes tested, burgundy bean and lablab seem the most likely to be profitably integrated into subtropical cropping systems. Further evidence of the rotational benefits provided by these legumes is required before they will be favoured over the perceived reliability and higher productivity of annual grass-type forages
Summer-growing perennial grasses are a potential new feed source in the low rainfall environment of southern Australia
Full text linkIn the Mallee region of southern Australia, the dry and variable climate results in frequent summer–autumn feed gaps, restricting the profitability of farms that combine livestock and crop enterprises. To assess the suitability of summer-growing perennial grasses to fill such feed gaps, two replicated field experiments comparing the persistence and productivity of several cultivars were conducted at Hopetoun and Karoonda. The data from these experiments also served to validate a C4 grass model, which was then used in a simulation experiment comparing productivity on two different soil types at three locations. Most grass cultivars established well except on sandy, non-wetting soils. At Hopetoun, four of five cultivars persisted over 6 years, demonstrating the tolerance of the selected cultivars to the typical long, dry summers and cold, wet winters of the region. Biomass production showed little difference between cultivars and a strong response to the amount of summer rainfall, ranging from 1500 to 3000 kg ha–1 under average seasonal conditions and peaking at 9000 kg ha–1 in the very wet summer of 2010–2011. Model performance was satisfactory (R2 0.85–0.93, RMSE 476–1673 kg ha–1, depending on the cultivar), in terms of predicting both the magnitude and the timing of biomass production. Simulation outputs indicated that biomass production closely followed seasonal trends in temperature and moisture availability. Grazing potential was highest from early summer to autumn, which coincides with the period of feed shortages and highest marginal value of forage. In areas with warm-season (October–April) rainfall averages of 175 and 225 mm, the grazing of C4 grass pastures on marginal soils would be possible in at least 40% of the years for 2 and 3 months, respectively. It was concluded that summer-growing perennials are a promising option to alleviate feed gaps on mixed crop–livestock farms in areas with at least 150 mm of rainfall from October to April
How beneficial are seasonal climate forecasts for climate risk management? An appraisal for crop production in Tanzania
Full text linkUnderstanding growing period conditions is crucial for effective climate risk management strategies. Seasonal climate forecasts (SCF) are key in predicting these conditions and guiding risk management in agriculture. However, low SCF adoption rates among smallholder farmers are due to factors like uncertainty and lack of understanding. In this study, we evaluated the benefits of SCF in predicting growing season conditions, and crop performance, and developing climate risk management strategies in Kongwa district, Tanzania. We used sea surface temperature anomalies (SSTa) from the Indian and Pacific Ocean regions to predict seasonal rainfall onset dates using the k-nearest neighbor model. Contrary to traditional approaches, the study established the use of rainfall onset dates as the criterion for predicting and describing growing period conditions. We then evaluated forecast skills and the profitability of using SCF in crop management with the Agricultural Production System sIMulator (APSIM) coupled with a simple bio-economic model. Our findings show that SSTa significantly influences rainfall variability and accurately predicts rainfall onset dates. Onset dates proved more effective than traditional methods in depicting key growing period characteristics, including rainfall variability and distribution. Including SCF in climate risk management proved beneficial for maize and sorghum production both agronomically and economically. Not using SCF posed a higher risk to crop production, with an 80% probability of yield losses, especially in late-onset seasons. We conclude that while SCF has potential benefits, improvements are needed in its generation and dissemination. Enhancing the network of extension agents could facilitate better understanding and adoption by smallholder farmers
Limits of conservation agriculture to overcome low crop yields in sub-Saharan Africa
Full text linkConservation agriculture (CA) has become a dominant paradigm in scientific and policy thinking about the sustainable intensification
of food production in sub-Saharan Africa. Yet claims that CA leads to increasing crop yields in African smallholder
farming systems remain controversial. Through a meta-analysis of 933 observations from 16 different countries in sub-Saharan African studies, we show that average yields under CA are only slightly higher than those of conventional tillage systems (3.7% for six major crop species and 4.0% for maize). Larger yield responses for maize result from mulching and crop rotations/intercropping. When CA principles are implemented concomitantly, maize yield increases by 8.4%. The largest yield benefits from CA occur in combination with low rainfall and herbicides. We conclude that although CA may bring soil conservation benefits, it is not a technology for African smallholder farmers to overcome low crop productivity and food insecurity in the short term
Improving the efficiency of use of small amounts of nitrogen and phosphorus fertilizer on smallholders maize in Central Malawi
No full textMineral fertiliser is a scarce input for smallholder maize farmers in Malawi. A recent provision of small amounts of subsidised fertilisers by government programmes to farmers throughout Malawi has increased fertiliser access and raised maize production, but fertiliser management and yield responses frequently remain poor. To seek ways to use the fertiliser more efficiently, we analysed the effects of low rates of N (15 or 30 kg N ha-1) and P (9 kg P ha-1) fertiliser in combination with improved weed management on maize yields in experiments on 12 smallholder farms in Chisepo, central Malawi. Several indices of N and P use efficiency were computed from the above-ground crop components and nutrient contents. Maize yield simulations were conducted using long-term rainfall records in the APSIM crop-soil system model. NP fertiliser significantly (p <0.001) raised maize grain yield from 0.65 to 1.5 t ha-1, and twice-weeding fertilised maize significantly (p <0.001) raised maize yields by 0.4 t ha-1 compared with weeding once (0.9 t ha-1). The agronomic efficiency of applied fertiliser N (AEN) averaged 19.3 kg grain kg N-1 with one weeding but doubled to 38.7 kg with the additional weeding. The physiological efficiency of applied N (PEN) was 40.7 kg grain kg-1 N uptake. APSIM predicted that similar or larger maize yield responses to 15 or 30 kg N ha-1 can be expected in 8 out of 10 years in areas with similar rainfall patterns to Chisepo. A financial analysis showed that the application of these small amounts of fertiliser was economic even when fertiliser was purchased from the open market, provided the crop was adequately weeded. Participatory assessments helped farmers understand the increased efficiency of fertiliser use possible with additional weeding, although some farmers reported difficulty implementing this recommendation due to competing demands for labour. We conclude that to raise the productivity and sustainability of fertiliser support programmes in Malawi, initiatives should be introduced to help identify and educate farmers on the major drivers of productivity in their systems
Break-crop effects on wheat production across soils and seasons in a semi-arid environment
Full text linkIn low-rainfall environments, a high frequency of cereal crops has been favoured for optimising productivity and risk. However, cereals at high intensity often lead to declining water-use efficiency and increasing inputs to cope with emergent nutritional, disease and weed problems. The value of including breaks in the cropping sequence can involve a high level of uncertainty in low-rainfall areas where non-cereal crops are more risky and profitability is largely determined by the subsequent benefit to cereal productivity. In this study, we aimed to improve understanding of the magnitude and primary source of break benefits such as nutrition, water and disease management in a low-rainfall environment where a high level of within-field soil variability can also contribute to uncertainty about the value of breaks. In on-farm field experiments near Karoonda in the South Australian Mallee, breaks were grown in 2009 or 2010 on four distinct soil types across a dune–swale catena. The effect of these breaks on subsequent cereal production was measured for up to 3 years. In addition, the effect of breaks on nutrition and water available, along with disease infection in subsequent cereal crops, was explored and actual yields were compared with nitrogen and water-limited potential yields. Consistent cumulative benefits to subsequent cereal crops of at least 1 t ha–1 after 3 years accrue from breaks grown on the different soil types. The inclusion of breaks had beneficial effects on the cycling and supply of nutrients along with some short-term impacts on infection by Rhizoctonia solani AG8 in subsequent cereals, whereas there were no conclusive effects of breaks on the supply of water to subsequent crops. This study suggests that the inclusion of both legume and brassica breaks is likely to be beneficial to subsequent cereal production where nitrogen is a factor limiting productivity in low-rainfall, semi-arid environments
Evaluation of the onset and length of growing season to define planting date -'a case study for Mali (West Africa)'
Full text linkThe agroecological zones (AEZ) of Mali fall within the semi-arid climate, the ability to determine efficiently or predict accurately the onset of growing season (OGS), and length of growing season (LGS) cannot be over-emphasized due to highly variable rainfall pattern and the dependence of smallholder farmers practising on rainfed farming agriculture. In this study, we determined the most suitable method for predicting the onset date of rainfall across AEZ that fitted with the planting windows of major cereal crops (maize, millet, and sorghum). Using long-term daily rainfall records from 22 meteorological stations spread across AEZ of Mali, four (4) known methods were applied to determine the onset dates of the rain. The mean onset dates were statistically compared with the farmer's planting window for the selected weather stations to determine the suitable dates of OGS and LGS. The hypothesis considered a time lag minimum of 7 days between the mean onset date and traditional farmer sowing dates for the crops. Then, the preferred method was used to estimate OGS based on early, normal and late dates respectively across the stations. Also, the estimated LGS according to each zone was evaluated using probability distribution chart with duration to maturity for varieties of the same crops. The results showed that Def_4 was found appropriate for Sahelian and Sudano-Sahelian zones; Def_3 satisfied the criteria and exhibited superior capacity into farmer's average planting date over Sudanian and Guinea Savannah zones. These results have an important application in cropping systems in order to prevent crop failure and ensure a better choice of crop variety according to LGS under climate variability and change being experienced across Mali
Understanding growth and development of three short-season grain legumes for improved adaptation in semi-arid Eastern Kenya
Full text linkShort-season grain legumes play an important role in smallholder farming systems as source of food and to improve soil fertility through nitrogen fixation. However, it is not clearly understood how these diverse legumes contribute to the resilience of such systems in semi-arid environments. We describe the growth, development and resource-use efficiency (focusing on radiation, RUE) of three promising short-season grain legumes: common bean (Phaseolus vulgaris L.), cowpea (Vigna unguiculata (L.) Walp.) and lablab (Lablab purpureus (L.) Sweet). Two field experiments were conducted during the short rains of 2012–13 and 2013–14 in Eastern Kenya. In the first experiment, the legumes were grown at three plant densities (low, medium, high); in the second experiment, they were subjected to three water regimes (rainfed, partly irrigated, fully irrigated). Phenological development was monitored and biomass accumulation, leaf area index and fractional radiation interception were measured repeatedly during growth; grain yield was measured at maturity. Harvest index and RUE were calculated from these data. Common bean had the shortest growing period (70 days), the most compact growth habit and relatively high RUE but limited grain yield (1000–1900 kg ha–1), thereby proving more suitable for cultivation in areas with restricted cropping windows or in intercropping systems. Cowpea had a longer growing period (90 days) and a spreading growth habit leading to high light interception and outstanding grain yields under optimal conditions (1400–3050 kg ha–1). Lablab showed stable RUE values (0.76–0.92 g MJ–1), was relatively unaffected by limited water availability and had a comparatively long growing period (100 days). Lablab grain yields of ~1200–2350 kg ha–1 were obtained across all water regimes, indicating a high potential to cushion climatic variability. Planting density strongly influenced the production success of cowpea and lablab, with high plant densities leading to vigorous growth habit with low podset establishment. Such information on temporal and spatial differences in growth, development and resource-use efficiency is highly valuable for crop-modelling applications and for designing more resilient farming systems with short-season grain legumes
Long-term cropping system studies support intensive and responsive cropping systems in the low-rainfall Australian Mallee
Full text linkContinuous-cropping systems based on no-till and crop residue retention have been widely adopted across the low-rainfall cereal belt in southern Australia in the last decade to manage climate risk and wind erosion. This paper reports on two long-term field experiments that were established in the late 1990s on texturally different soil types at a time of uncertainty about the profitability of continuous-cropping rotations in low-rainfall environments. Continuous-cereal systems significantly outyielded the traditional pasture–wheat systems in five of the 11 seasons at Waikerie (light-textured soil), resulting in a cumulative gross margin of AU$1600 ha–1 after the initial eight seasons, almost double that of the other treatments. All rotation systems at Kerribee (loam-textured soil) performed poorly, with only the 2003 season producing yields close to 3 t ha–1 and no profit achieved in the years 2004–08. For low-rainfall environments, the success of a higher input cropping system largely depends on the ability to offset the losses in poor seasons by capturing greater benefits from good seasons; therefore, strategies to manage climatic risk are paramount. Fallow efficiency, or the efficiency with which rainfall was stored during the period between crops, averaged 17% at Kerribee and 30% at Waikerie, also indicating that soil texture strongly influences soil evaporation. A ‘responsive’ strategy of continuous cereal with the occasional, high-value ‘break crop’ when seasonal conditions are optimal is considered superior to fixed or pasture–fallow rotations for controlling grass, disease or nutritional issues
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