Soil Water Management Practices Research Articles

Climate Change Responses of Cocoa Farmers in Ghana

Background: Undoubtedly, vulnerability and adaptation of the agricultural sector to the adverse impacts of climate change are among the most crucial concerns of many developing countries where agriculture is largely rain-fed. In Ghana, the cocoa sector is the mainstay of the agricultural sector, contributing about 60% of agricultural GDP. The cacao tree is susceptible to the vagaries of climate, a fact which manifests in outbreak of pests and diseases and their pattern, loss of pods and early ripening of young pods, among others. Cocoa farmers have over the years used short-term (coping) strategies and long-term (adaptation) strategies to offset the effects of climate change on their production.
 Methods: A field survey of 444 cocoa farmers in Ghana was conducted, using a guided interview schedule.
 Results: Farmers’ coping strategies included those on crop, soil fertility and soil water management practices. Adaptation strategies included behavioural adjustments (spraying, fertilizer application, weed control, pruning) as well as institutional and technological adjustments (change in variety and increased extension services).
 Conclusion: The study showed that farmers who perceived that the climate had changed and had some effect on their production usually employed adaptation measures. Differences in farmers in terms of personal managerial and entrepreneurial capacities and family circumstances influence their responses to climate change. However, one major challenge is to separate the adaptations in response to climate change from adaptations in response to other stimuli, such as market price or government policy changes that farmers face in the real world. Assessing adaptation strategies also provides the information needed by cocoa farmers to increase their capacity to moderate potential damages and to take advantage of opportunities, if any, to survive in a changing climate.

Soil water management practices (terraces) helped to mitigate the 2015 drought in Ethiopia

While the benefits of soil water management practices relative to soil erosion have been extensively documented, evidence regarding their effect on yields is inconclusive. Following a strong El-Niño, some regions of Ethiopia experienced major droughts during the 2015/16 agricultural season. Using the propensity scores method on a nationally representative survey in Ethiopia, this study investigates the effect of two widely adopted soil water management practices – terraces and contour bunds – on yields and assesses their potential to mitigate the effects of climate change. It is shown that at the national level, terraced plots have slightly lower yields than non-terraced plots. However, data support the hypothesis that terraced plots acted as a buffer against the 2015 Ethiopian drought, while contour bunds did not. This study provides evidence that terraces have the potential to help farmer deal with current climate risks. These results can inform the design of climate change adaptation policies and improve targeting of soil water management practices in Ethiopia.

Photosynthetic Response of Maize to Nitrogen Fertilization in the Semiarid Western Loess Plateau of China

Agriculture in rainfed dry areas is often challenged by inadequate water and nutrient supplies. Responses to these challenges include adequate fertilization, but it is unknown whether different nitrogen (N) rates from that commonly used in the Loess Plateau can alleviate this issue. Field experiments were conducted over three cropping seasons to investigate the effect of different N fertilization levels on soil water dynamics, photosynthetic activity, and grain yield of maize (Zea mays L.) grown in the Western Loess Plateau of China. Fertilizer was applied at planting at rates between 0 and 300 kg N ha−1 at regular increments of 100 kg N ha−1 (referred to as N0 and N300, respectively), and treatments were arranged in a complete randomized block design. Results showed that water use efficiency in the N200 and N300 treatments was ∼60% higher than N0 and N100 (P < 0.05), which translated into increased crop biomass and therefore grain yield (≈70–80%). These observations were consistent with all measurements of photosynthetic traits and suggested that, under the conditions of this study, the ecophysiological response of the crop may be optimized at N application rates in the range of 200 to 300 kg ha−1, depending on soil water availability. Agronomic efficiency calculations at this level of N fertilization reported consistently higher values and consequently suggested that environmental losses of applied fertilizer N were small. The current experimental results for the N application rates in the range of 200 to 300 kg ha−1 could be useful for improving N fertilizer and soil water management practices of maize production while maintaining a relatively stable yield level in rainfed dry areas. Future work should focus on optimizing timing and improving the placement of fertilizer N applied to maize.

Changing rainfall patterns and farmers’ adaptation through soil water management practices in semi-arid eastern Kenya

ABSTRACTThere is limited documentation of soil and water management technologies that enhance adaptation to climate change in drylands of Kenya. Rainfall patterns were analyzed in the semi-arid Machakos and Makueni counties of eastern Kenya using historical data. A total of forty-three smallholder farmers implementing soil water management practices were sampled, and an estimate of the seasonal water budget for current crop and livestock production systems computed. Analysis of rainfall amounts and distribution shows increasing variability, with the average annual total amounts decreasing over the past 50 years. Furthermore, the number of rainy days within the March-April-May season that can support crop growth is gradually decreasing. These decreases are however not significant at P < 0.05. There were more seasons with low rainfall amounts compared to those with high rainfall amounts. All these subject the smallholder crop and livestock production system to limited soil moisture. Farmers address the risk by harnessing and utilizing green (rainfall stored in soil) and blue (rainfall collected into storage tanks) water technologies. The study found that farmers in these semi-arid counties practice fifteen diverse soil and water management interventions on their farms. The most popular practices are cut-off drains, retention ditches, terracing, run-off harvesting, and agroforestry. The estimated seasonal water budget indicates the need for integrated soil and water management interventions to address the crop and livestock production constraints.

Spatio-temporal variability and temporal stability of water contents distributed within soil profiles at a hillslope scale

Information about soil water content (SWC) within soil profiles in terms of its spatio-temporal variability and temporal stability is crucial when selecting appropriate soil water management practices. However, detailed profile distribution features for related indices are not clear on the Chinese Loess Plateau. This study aimed to investigate the depth dependency of spatio-temporal variability and temporal stability of SWC at the hillslope scale using an intensive sampling strategy for both horizontal and vertical directions as well as over time. The SWCs at 20 depths within 0–300cm soil profiles were measured on 20 occasions between July 2008 and October 2010 at 91 locations on a hillslope on the Loess Plateau, China. Results showed that although the profile distributions of investigated statistical parameters differed greatly, they were all depth dependent. Based on both the spatio-temporal variability and the temporal stability characteristics using eight indices, the studied soil profile (0–300cm) could be divided into three soil layers, i.e., 0–60, 60–160 and 160–300cm, with a characteristic feature of “irregularly changing”, “regularly changing”, and “relatively constant”, respectively. The deepest rainwater replenishment depth was approximately 160cm. Therefore, choosing 200cm as the sampling depth would be sufficient in similar areas. Such findings are useful for designing an optimal strategy for sampling and management of profile soil moisture.

Temporal stability of soil water storage under four types of revegetation on the northern Loess Plateau of China

Conservation of soil water and restoration of vegetation have long been major subjects of concern on the northern Loess Plateau. Revegetation with species such as Korshinsk peashrub (KOP) and purple alfalfa (ALF), as well as with natural revegetation of fallow areas (NAF) have been used extensively. This paper examines the temporal stability of soil water storage (SWS) under these different revegetation types, including under millet (MIL) crops for comparison, grown in adjacent plots on a hillslope intending to provide information relevant to the strategic guidance of revegetation and soil water management practices. SWS was measured at 10-cm intervals in the soil profile to a depth of one meter using a neutron probe on 11 occasions between 2010 and 2011. The results indicated that: (1) time-averaged SWS relative to MIL decreased in the order of KOP (49.4mm), ALF (32.4mm) and NAF (14.9mm) implying that shortages of soil water were induced largely by revegetation and were affected by the plant species. (2) Frequency distributions showed that points with probabilities of 0.5 were not stable between extreme soil water conditions; however, this result might be mitigated or avoided by increasing the sampling density and/or conducting measurement over a longer period. (3) Based on relative difference analysis, the most stable data points underestimated the mean SWS of the plots but were still valuable for precisely estimating the mean SWS of the experimental plot; in addition, among methods for estimating the plot average using representative points, directly using the value of relative difference or their standard deviation, or an index of temporal stability or the mean absolute bias error, no one method consistently performed better than another. (4) ALF presented the most temporally stable patterns among all types of revegetation tested, and vegetation cover and aboveground biomass were the main factors affecting SWS temporal stability. (5) Temporally stable points were located at the mid-slope of the plots. In conclusion, when temporal stability theory was applied to sloping lands mid-slope sampling is likely to give the best results but vegetation characteristics, and in particular vegetation cover should be highlighted.

Soil–water conservation and rainwater harvesting strategies in the semi-arid Mzingwane Catchment, Limpopo Basin, Zimbabwe

Various soil water management practices have been developed and promoted for the semi arid areas of Zimbabwe. These include a variety of infield crop management practices that range from primary and seconday tillage approaches for crop establishment and weed management through to land forming practices such as tied ridges and land fallowing. Tillage methods evaluated in this study include deep winter ploughing, no till tied ridges, modified tied ridges, clean and mulch ripping, and planting basins. Data collected from the various trials since the 1990s show that mulch ripping and other minimum tillage practices consistently increased soil water content and crop yields compared to traditional spring ploughing. Trial results also showed higher soil loss from conventionally ploughed plots compared to plots under different minimum tillage practices.

Improvement of water application efficiency by moisture conservation methods for establishment of planted tree seedlings

The survival rate of transplanted tree seedlings in the afforestation and reforestation programs of Ethiopia has been very often low due to, among others, inadequate soil moisture particularly during the establishment period. Irrigation of seedlings and conserving moisture at the early stage of growth in areas with inadequate rainfall can improve survival. The efficiency of water application can be improved not only through technical and technological consideration of the irrigation hardware (equipment and structures), but also through the application of appropriate soil water management practices. The principles underlying soil moisture movement under different soil conditions were applied on improvement of irrigation application efficiency for the establishment of transplanted tree seedlings at Alemaya Research Station. The principle that a coarser soil layer underlying a given soil prevents, in an unsaturated condition, its penetration by the moisture front, was used in Acacia saligna seedlings. This method of moisture conservation using a sand layer was also tested in combination with surface and vertical organic mulching. Three liters of water was applied to the individual seedlings planted in 2×2 m at a four‐day interval. A higher flesh biomass yield, plant height, and collar diameter were observed using the sand layer. Surface mulching used in combination with sand layer showed the highest value. The soil moisture content measured at 20 cm and 40 cm of the root depth was lower in the control treatment of tree seedlings without sand layer and mulching.

Spatial Variability of Evaporation along Two Transects of a Bare Soil

AbstractEstimates of soil water evaporation are required for the assessment of soil water management practices. The purpose of this study was to investigate (i) the spatial and temporal changes in soil water evaporation along two transects in a bare soil, (ii) the spatial variability in soil properties, and (iii) the comparison of field‐measured and simulated evaporation. The study was conducted on an Olton sandy clay loam soil (fine, mixed, thermic Aridic Paleustoll) at Lubbock, TX. Two 50‐m transects were oriented in north‐south and east‐west directions with sampling positions marked at 1‐m intervals. A 150‐mm irrigation was applied and soil water evaporation was measured for the four succeeding days. Particle‐size distribution and bulk density were determined from each sample after the last measurement. Semivariograms were calculated for each parameter along with the population statistics. Evaporation values were isotropic between transects for the first 3 d of measurement and did not exhibit any particular range for the semivariograms. We conclude that random samples can be taken to quantify soil water evaporation rates within this bare field. Population statistics for the bulk density revealed that the populations were random, normal distributions with no spatial structure, and for particle size the populations were either normal or log‐normal. Values of soil water evaporation from the CONSERVB model were within one standard deviation of the mean of measured values when average soil hydraulic properties for the field were used. It is possible to use the average soil properties as input into a model for regional assessment of soil water evaporation rates.

Water use by soybean in two soils with and without irrigation

Water use and seed yield of soybeans ( Glycine max. L.), grown on two soils with and without irrigation were investigated. Seed yield, in each soil type, was significantly correlated to water use. Most of the differences in water use, between the irregated versus dryland treatments, in each soil type, occurred during the podfill growth stage. The podfill growth stage water use, in the irrigated treatment of each soil type, was almost twice that in the corresponding dryland. The podfill growth stage water use, irrespective of the treatments, varied with the soil type. This was attributed to the differences in the contribution of preplant profile stored water between the soil types. The contribution of preplant profile storage, in one soil type, to podfill growth stage water use was similar to the rainfall received during this growth stage in this soil type. However, in the second soil type the corresponding contribution was almost three times that of the rainfall. The results indicated soybean seed yield benefitted most from irrigation during the podfill growth stage. The results suggests the information in preplant profile storage, availability and use, in conjunction with rainfall is useful in developing appropriate soil water management practices.