NUTRITION AND WATER MANAGEMENT IN INTENSIVE PEAR GROWING

Abstract

Mineral nutrition and irrigation are key management practices in fruit production worldwide. In this presentation, that is grower oriented, I will emphasize basic concepts trying to wrap up elementary information collected from past studies and grower’s experience. The easy approach of nutrient management has been the addition of fertilizers, usually nitrogen (N) based on the concept that this nutrient is deficient in most soils and required by the trees to achieve fruit and shoot growth. Although the argument is true, a nutrient program should consider many inputs starting with the knowledge of the physical and chemical properties of the soil, root zone distribution, facts of the orchard system (rootstock, cultivar, tree density), nutrient dynamics in the soil and within the tree, crop load and fruit quality among the important ones. Generally speaking all that makes up what we call “diagnostic tools”. Regardless orchard system, the tree physiology is unique. Each pear growing region in the world has its own framework. Argentina, which is the first leading exporting country for pear is characterized by the use of the seedling rootstock that leads to tree spacing not less than 4A—2 m. In the USA and South Africa, also semi-vigorous rootstocks are the most popular but the irrigation system is by drip or sprinklers rather that flood as in Argentina. However, in Europe, medium and high density plantations are possible by using quince as a dwarfing rootstock. Spite the disparity of the pictures in those regions, the way the trees function is the same what varies is the strategy to managing the orchard and mineral nutrition is not an exemption. Thus, research in the last two decades showed that N was not required in large amounts for pome fruits. Pears demand 50-60 kg ha-1 to retain good fruit quality and production. The use of the stable isotope N15 allowed researchers to fine tune N application timing because the partitioning of the nutrient at each stage of growth during the season was clearly defined. Also the role of reserves and the estimation of N resorption in the fall were key findings that lead to a more efficient and sustainable N managements in orchards. Any given fertilizer program cannot be successful without an efficient irrigation program. Water is scarce in most pear districts for both quantity and quality. Regulated deficit irrigation has proven to be a good strategy to save water with minimal impact on production. New tools for water monitoring in both soils and trees allow growers to optimize irrigation water use. This area of research is ongoing in most countries along with studies leading to new rootstocks tolerant to low quality water, mainly salts and toxic minerals like boron. The goal of all growers is to produce high yield of good quality fruit and that is function of many decisions that should be taken considering the orchard system as a whole. Diagnostics tools and knowledge of tree physiology allow growers to take better decisions. The most modern management tool can be useless if one ignores the fundamental concepts.