RAINFED AGRICULTURE IN HAITI (A PRACTICAL MANUAL) by GEORGE H. HARGREAVES AND ZOHRAB A. SAMANI INTERNATIONAL IRRIGATION CENTER DEPARTMENT OF AGRICULTURAL AND IRRIGATION ENGINEERING LOGAN, UTAH 84322 April, 1983 TABLE OF CONTENTS Page INTRODUCTION ................................. ........ 1 CROPS AND POTENTIAL YIELDS ....................... 3 CROP WATER REOUIREMENTS .................................... 5 RAINFALL PROBABILITIES ...... ...................... 6 MOISTURE AVAILABILITY INDEX ............................... 7 RAINFALL INTENSITIES ....................................... 8 MAXIMIZING YIELDS .................. ............ 9 CROP SELECTION .......................................... 12 CROP SUITABILITY ZONING................ ... ............. 21 LIMITATIONS ................................................ 24 THE APPENDICES ............................................. 25 REFERENCES ................................................. 26 APPENDIX A - RAINFALL PROBABILITIES, CLIMATIC DATA, POTENTIAL EVAPOTRANSPORATION AND THE MOISTURE AVAILABILITY INDEX .................. A-I APPENDIX B - METHODS AND EOUATIONS USED ................... B-I APPENDIX C - COMPUTER PROGRAM USED TO PRODUCE APPENDIX A.. C-i LIST OF TABLES Table 1 - Good Yields of High Producing Varieties Under Adequate Water Supply and High Level of Agricultural Inputs, Crop Coefficients and Yield Reduction Factors ....................... 4 Table 2 - Time for Planting to Maturity for Hybrid Maize:: II Table 3 - Crop Adaptability Inventory Group I...... 16 Table 4 - Crop Adaptability Inventory - Gorup II.......... 17 Table 5 - Crop Adaptability Inventory - Group III ......... 18 Table 6 - Crop Adaptability Inventory - Group IV.......... 19 Table 7 - Crop Adaptability Inventory - Group V .......... 20 LIST OF FIGURES Figure 1 - Average Relationships Between Maximum Leaf Photosynthesis Rate and Temperature for Crop Groups I, II, III, and IV..................... 13 Figure 2 -Crop Suitability Zones ........................ 27 ii INTRODUCTION Haiti has favorable climatic conditions for the production of most tropical crops. Large areas of good quality soils are found in the plains and valleys. During hurricanes rainfall is often intense and with the increasing cultivation in the mountains flooding and erosion have become serious problems. During the French Colonial period about 14,000 ha were irrigated. This was considerably less than the maximum irrigable area. About 900,000 ha are classed as arable. However, the major portion of these arable lands is of limited agricultural potential. Agriculture is the principle economic activity contributing over 60 percent of foreign exchange earnings. Unfortunately emphasis is rapidly shifting towards the farming of steep mountain slopes. The hillside and mountainside agriculture increases erosion, causes greatly increased flood damage in the plains and rapidly degrades the total agricultural resource potential. This study indicates how a knowledge of rainfall and climate can be used to increase agricultural production from rainfed agriculture. The concepts developed herein apply to irrigated agriculture also but emphasis is proposed for the approximate 80,000 ha of non-irrigated lands classed as arable. It is evident that well planned investments in improving production on these lands is one of the most profitable of agricultural developments possible in Haiti. Care is recommended so that every possible effort be made to discourage the production of cultivated annual crops on slopes so steep that erosion is or will be a problem. Efforts are required so as to I improve production on lands capable of sustained use. As production is increased on the lands subject to only modest rates of erosion there will then be less need to produce food or the steep mountainsides. Haiti once supplied two-thirds of the overseas trade of France and was described as the greatest agricultural colony in the world. This high level of agricultural production was principally from irrigated plantations in the plains. That irrigated potential can with proper conservation be restored. In addition a large rainfed potential is capable of making a major contribution to the food supply and to the economy. The climatic potential for agricultural production based upon monthly data is herein well documented. Additional effort is recommended relative to soils and also with respect to crop marketing and commercialization. The information presented provides much of the knowledge required for technology transfer, for agricultural demonstrations, for designing research and for improving agricultural productivity. Tables are presented that indicate the length of the growing season for rainfed crops and mean monthly temperatures so that crops suitable to the local climate may be selected. A map at the scale of 1:1,000,000 indicates zones of similar rainfall and length of rainy season. The degree of adequacy of water as indicated by the zones indicates the level of potential production. Experimental results or technology developed within a zone can usually be transferred to other locations within the same zone. 2 CROPS AND POTENTIAL YIELDS The yield of a given crop depends upon a variety of factors including water availability, temperature, solar radiation and fertility or the availability of plant nutrients. Table 1 lists crops that are climatically suitabl2 for the prevailing conditions of fairly adequate water and fertility. These levels of production can frequently be exceeded by 50 percent or more providing all agricultural inputs and climatic conditions are near optimum. Good yields can only be attained when water is reasonably adequate during the crop growing season. Water use falls off as the crop matures and water deficits are less limiting on yields during this period. In general a full water supply is required for nearly the full number of days to maturity (Column 2 of Table 1). The fertilizer recommendations (Columns 4, 5 and 6) are from Doorenbos, et al, (1), and provide a guide for estimating the amounts necessary for good yields. The recommendations for nitrogen are generally conservative. The requirements for phosphate and potassium are quite variable depending upon soil conditions. By constructing graphs or isoquants of crop yield as a function of seasonal crop evapotranspiration in mm, ET, and nitrogen applied in kg per ha, N, optimization lines were drawn for several crops. The data used were composite principally from several states in the United States. For maize (corn) a prinicpal source was data from Israel. Two of the optimization equations are given as follows: 3 Table 1. Good Yields of High Producing Varieties Under Adequate Water Supply and High Level of Agricultural Inputs, Crop Coefficients and Yield Reduction Factors. Days to Potential Recommended Fertilizer kg /a) Crop Maturity Yield ton/ha N P K KC y (1) (2) (3) (4) (5) (6) (7) (8) Banana 300-365 40-60 200-400 45-60 240-480 0.70 1.27 Beans 90-120 1.5-2.5 20-40 40-60 50-120 0.70 1.15 Cotton 150-180 3-4 100-180 20-60 50-80 0.80 0.85 Grapefruit 240-365 35-50 100-200 35-45 50-160 0.65 0.95 Groundnut 90-115 3-4 10-20 15-40 25-40 0.75 0.70 Kenaf 100-125 40-50 175 30 85 Maize 75-140+ 6-8 100-200 50-80 60-100 0.75 1.25 Millet 60-90 2-4 see sorghum Mungbean 45 or more 2.5-2.8 see groundnut Pineapple 365 75-90 230-300 45-65 110-220 Rice 90-180 6.0-8.0 100-150 20-40 80-120 Sesame 1.05 85-150 1-2 50 20 15 Sorghum 90-140 3.5-5 100-180 20-45 35-80 0.75 0.90 Soybean 75-150 2.5-3 10-20 15-30 25-60 0.75 n.85 Sunflower 90-130 2.5-3.5 50-100 20-45 60-125 0.75 0.95 Sugarcane 270-365 110-150 150 50-70 100-160 0.85 1.20 Tobacco 90-120 2.0-2.5 40-80 30-90 50-11N 0.85 0.90 Tomato 90-140 45-65 100-150 65-110 160-240 0.75 1.05 Watermelon 80-110 25-35 80-100 25-60 35-80 0.75 1.10 ky = Yield Reduction Factor Sources: A) Samuel C. Litzenberger, editor (6) B) Doorenbos, et al. (1) C) Miscellaneous Crop Equation Maize (Corn) N = 0.32 ET Cotton N = 0.10 ET Analysis of data from other crops not commonly grown in Haiti indicate that for most non-legumenous crops the coefficient in the equation is in the range of 0.10 to 0.15. These values are furnished as a guide and should be confirmed through research and demonstration. Column 7, the crop coefficient, KC, is an indication of the seasonal crop water requirements. A KC value of 0.70 indicates that crop evapotranspiration ET (crop) for the season should equal about 0.70 times the seasonal total potential evapotranspiration, ETP. If ET (crop) is less than this amount a corresponding reduction in yield can be anticipated resulting in somewhat less than good yields. Column 8 gives the yield reduction factor, ky. The overall average value of ky is approximately 1.00 but varies with the crop from 0.70 for groundnut to 1.27 for banana. A value of ky = 1.25 for maize indicates that a 10 percent reduction of ET (crop) from the required amount will produce a crop yield reduction of 12.5 percent. In the case of groundnuts a 10 percent reduction in ET (crop) would produce a yield reduction of 7 percent. CROP WATER REOUIREMENTS Water requirements vary with the crop, with crop stage of growth and sometimes different varieties of the same crop have significantly different water requirements. The requirements are usually estimated by 5 applying crop coefficients KC to some reference such as Class A pan evaporation from a pan located in a well standardized irrigated area or to reference crop evpotranspi ration or calculated potential evapotranspiration, ETP. For this study one of the simplest yet more accurate and reliable methods for estimating potential evapotranspiration, ETP, was used. This method is described in Appendix B, Methods and Equations used. Crop water requirements are determined by multiplying values of ETP by KC for the crop season or fo' each growth stage period. References to sources of crop coefficients, KC, are given in Appendix B.