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M alnutrition is the most chronic and pressing agricultural and human health problem of the 21st century. Undernutrition, micronutrient malnutrition, and unbalanced overnutrition with excessive consumption of carbohydrates and fats aff ect at least one third of the world's population in a negative manner and impinge on both longevity and the quality of life with good health. Yet in diff erent regions of the world, in developing and developed countries alike, a similar change in diet is occurring: Relearning ABSTRACTDiversifying diets and agricultural enterprises with fruit and vegetables is a potent weapon in the current global battle against malnutrition and poverty. Agricultural science can contribute substantially to enhance the development prospects and health of not only disadvantaged and vulnerable individuals at one end of the spectrum but also the growth and equity of national economies at the other. Moreover, with relatively simple applied research, new crop species and technologies can rapidly enter the development pathway to benefi t even the poorest people or nations. More upstream research can help to guard fruit and vegetable production against the vagaries of potential climatic uncertainty, which is projected to become more prominent over future decades. However, historical and continuing widespread underinvestment in fruit and vegetable research and development from the national to the global level may severely compromise the world's ability to use such highvalue species for crop diversifi cation and as a major engine of development growth to ensure global food and nutritional security.

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Grape is a major fruit crop which occupies 33% of the total area of fruit cultivation in Yemen. Grape vines are cultivated under both irrigated and rainfed production systems. The irrigation practices in grape orchards are traditional with low efficiency due to high losses of water. In order to obtain rapid and reliable results, the comparison of five equations for calculation of evapotranspiration and obtaining the Kc values by utilizing actual evapotranspiration of grape became necessary. Crop water requirement of grape trees in Sawan, Bani Hushaish District in Sana'a Governorate was studied and two methods of irrigation were investigated for two years (2005-2006). The investigated irrigation methods were: bubbler (localized) irrigation and basin irrigation. Results indicated the significant superiority of bubbler irrigation over the basin irrigation. The actual water requirements reached 601 and 736 mm water depth respectively with application efficiency reaching 82.6% and 69.8% respectively. The irrigation water productivity of the bubbler irrigation was significant (3.8 kg/m3) while it was less under basin irrigation (1.8 kg/m3). Results indicated that the average crop coefficient throughout the growing season ranged from 0.42 in the case of using Ivanov equation and 0.75 in the case of Hargreaves. In addition to standard FAO Penman-Monteith equation, the Hargreaves and Blaney-Criddle are the best equations that can be used in determination of crop water requirements and irrigation scheduling of grapes. It was also observed that the highest crop coefficient was recorded in the months of May and June in all treatments