Evaluation of Crop Models for Simulating and Optimizing Deficit Irrigation Systems in Arid and Semi-arid Countries Under Climate Variability

Water scarcity and quality degradation represent real threats to economic, social, and environmental development of arid and semi-arid regions. Drip irrigation associated to Deficit Irrigation (DI) has been investigated as a water saving technique. Yet its environmental impacts on soil and groundwater need to be gone into in depth especially when using brackish irrigation water. Soil water content and salinity were monitored in a fully drip irrigated potato plot with brackish water (4.45 dSm−1) in semi-arid Tunisia. The HYDRUS-1D model was used to investigate the effects of different irrigation regimes (deficit irrigation (T1R, 70% ETc), full irrigation (T2R, 100% ETc), and farmer’s schedule (T3R, 237% ETc) on root water uptake, root zone salinity, and solute return flows to groundwater. The simulated values of soil water content (θ) and electrical conductivity of soil solution (ECsw) were in good agreement with the observation values, as indicated by mean RMSE values (≤0.008 m3·m−3, and ≤0.28 dSm−1 for soil water content and ECsw respectively). The results of the different simulation treatments showed that relative yield accounted for 54%, 70%, and 85.5% of the potential maximal value when both water and solute stress were considered for deficit, full. and farmer’s irrigation, respectively. Root zone salinity was the lowest and root water uptake was the same with and without solute stress for the treatment corresponding to the farmer’s irrigation schedule (273% ETc). Solute return flows reaching the groundwater were the highest for T3R after two subsequent rainfall seasons. Beyond the water efficiency of DI with brackish water, long term studies need to focus on its impact on soil and groundwater salinization risks under changing climate conditions.

Download Full-text

Forecasting the impacts of climate variability: lessons from the rainfed corn market in Ceará, Brazil

Environment and Development Economics ◽

10.1017/s1355770x07004172 ◽

2008 ◽

Vol 13 (2) ◽

pp. 201-227 ◽

Cited By ~ 11

Author(s):

ARIASTER B. CHIMELI ◽

FRANCISCO DE ASSIS DE SOUZA FILHO ◽

MARCOS COSTA HOLANDA ◽

FRANCIS CARLO PETTERINI

Keyword(s):

Climate Variability ◽

Developing Economies ◽

Arid Zone ◽

Well Being ◽

Policy Makers ◽

Local Climate ◽

The World ◽

Forecast Models ◽

Climatic Impacts ◽

Semi Arid

ABSTRACTA number of studies show that climatic shocks have significant economic impacts in several regions of the world, especially in, but not limited to, developing economies. In this paper we focus on a drought-related indicator of well-being and emergency spending in the Brazilian semi-arid zone – rainfed corn market – and estimate aggregate behavioral and forecast models for this market conditional on local climate determinants. We find encouraging evidence that our approach can help policy makers buy time to help them prepare for drought mitigating actions. The analysis is applicable to economies elsewhere in the world and climatic impacts other than those caused by droughts.

Download Full-text

Evaluation of Very High Soil-Water Tension Threshold Values in Sensor-Based Deficit Irrigation Systems

Journal of Irrigation and Drainage Engineering ◽

10.1061/(asce)ir.1943-4774.0000722 ◽

2014 ◽

Vol 140 (9) ◽

Cited By ~ 6

Author(s):

Sebastian Kloss ◽

Niels Schütze ◽

Urs Schmidhalter

Keyword(s):

Soil Water ◽

Deficit Irrigation ◽

Threshold Values ◽

Irrigation Systems ◽

Soil Water Tension ◽

High Soil ◽

Water Tension ◽

Very High

Download Full-text

CLIMATE VARIABILITY AND CHANGE: FARMER PERCEPTIONS AND UNDERSTANDING OF INTRA-SEASONAL VARIABILITY IN RAINFALL AND ASSOCIATED RISK IN SEMI-ARID KENYA

Experimental Agriculture ◽

10.1017/s0014479710000918 ◽

2011 ◽

Vol 47 (2) ◽

pp. 267-291 ◽

Cited By ~ 91

Author(s):

K. P. C. RAO ◽

W. G. NDEGWA ◽

K. KIZITO ◽

A. OYOO

Keyword(s):

Climate Variability ◽

Crop Production ◽

Smallholder Farmers ◽

Crop Productivity ◽

General Tendency ◽

Climate Variability And Change ◽

Negative Impacts ◽

Probabilistic Nature ◽

Semi Arid

SUMMARYThis study examines farmers’ perceptions of short- and long-term variability in climate, their ability to discern trends in climate and how the perceived trends converge with actual weather observations in five districts of Eastern Province in Kenya where the climate is semi-arid with high intra- and inter-annual variability in rainfall. Field surveys to elicit farmers’ perceptions about climate variability and change were conducted in Machakos, Makueni, Kitui, Mwingi and Mutomo districts. Long-term rainfall records from five meteorological stations within a 10 km radius from the survey locations were obtained from the Kenya Meteorological Department and were analysed to compare with farmers’ observations. Farmers’ responses indicate that they are well aware of the general climate in their location, its variability, the probabilistic nature of the variability and the impacts of this variability on crop production. However, their ability to synthesize the knowledge they have gained from their observations and discern long-term trends in the probabilistic distribution of seasonal conditions is more subjective, mainly due to the compounding interactions between climate and other factors such as soil fertility, soil water and land use change that determine the climate's overall influence on crop productivity. There is a general tendency among the farmers to give greater weight to negative impacts leading to higher risk perception. In relation to long-term changes in the climate, farmer observations in our study that rainfall patterns are changing corroborated well with reported perceptions from other places across the African continent but were not supported by the observed trends in rainfall data from the five study locations. The main implication of our findings is the need to be aware of and account for the risk during the development and promotion of technologies involving significant investments by smallholder farmers and exercise caution in interpreting farmers’ perceptions about long-term climate variability and change.

Download Full-text