Abstract
Rainfed areas in Mexico accounts for 14 million hectares where around 23 million people live and are located in places where there is a little climatic information. The severe drought that has impacted northern Mexico in the past several years as well as other parts of the country, has forced decision takers to look for improved tools and procedures to prevent and to cope with this natural hazard. For this paper, the methodology of the Food and Agricultural Organization of the United Nations (FAO) for estimating water balance variables was modified to provide crop yield estimations under rainfed agriculture in maize producer states of Mexico. The water balance accounts for the daily variation of soil water content having main input rainfall (Pp) and main output crop evapotranspiration (Eta). The algorithm computes crop yield using two distinctive approaches: 1) one based on surplus/deficit functions for each crop considered and 2) yield estimations based on soil water balance and water function productions of the crop being analyzed. For computing water balance and crop yields, a computer model is built that incorporates the FAO method for water balance (MODEL SICTOD: Computational System for Decision Taking, acronym in Spanish) which stochastically generate precipitation based on wet/dry transition probabilities using a first order Markov chain scheme. Maps of average crop yields were obtained after interpolating model outcomes for the main maize producer states of Mexico: Jalisco, Michoacan, Guerrero, Puebla Oaxaca and Chiapas. Different planting dates were analyzed, early (90 days of length period), intermediate (120 days of length period) and late (150 days of length period). Crop yield variability correlates to the transition probability on having a wet day following a dry day. Results have shown high yield variation and probability of crop yield failure and climatic risk follows a distinctive pattern according to planting date and rainfall occurrence. The approach used is of great support for decision taking processes.
Highlights
The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) states that the world has been more drought-prone during the past 25 years and that climate projections indicate an increased frequency in the future
Deterministic models are incapable of predicting future scenarios. They quantify actual outcomes based on historical records. Under this framework the objective of the study is to compute maize yield in main maize producing rainfed areas in Mexico, utilizing a computer model that incorporates a modification of the soil water balance of FAO
The consideration of the 25% of initial soil water content comes from several samples in the field where we found that when the producers plant the crop in rainfed areas the soil water content in the upper soil layer (≈30 cm) is barely that amount
Summary
The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) states that the world has been more drought-prone during the past 25 years and that climate projections indicate an increased frequency in the future. This carries significant implications for the agriculture sector, especially in the developing countries. Drought is considered as an abnormal water deficit in at least one part of the land surface hydrological cycle. It can be described in three dimensions: intensity, duration, and the area it covers; it differs from aridity, which is restricted to low rainfall regions [1]. When the impacts of a drought are severe, depending on people capacity to cope with the situation, the last resort is to emigrate to other states or to the US [2]
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