Optimizing Irrigation and Nitrogen for Quality, Yield, Endogenous Ethylene, Respiration, and Mineral Partitioning in Fuji Apple Fruit
The increasing world population and discoveries of the health benefits of fruits mandate higher production of fruits worldwide. Also, water supplies are becoming more scarce. Thus, the use of a highly efficient irrigation system in a high density orchard is extremely important for todays modern apple production. Quantity and method of irrigation and amount of nitrogen (N) application play major roles in apple fruit quality and yield. Irrigation method affects water usage, which is becoming a very critical issue in many parts of the world including the Pacific Northwest. On one hand, apple growers prefer a sprinkler system for orchard floor management. On the other hand, increasing pressure for lower water usage necessitate use of drip systems in the future. Injection of nutrients through irrigation systems, called fertigation, is a popular
method for application of nutrients. Among all applied nutrients, precise fertigation of N is more important than other mineral elements as excess N application decreases fruit color and increases fruit ethylene and respiration. In our recent study, we have found that as compared to a sprinkler system, a well-designed drip system can reduce water consumption while producing fruits with comparable or higher quality and yield. However, irrigation through a micro-jet sprinkler system is extremely important for development of orchard floor cover grass and for a cooler environment. Research has been conducted with orchard fertigation through drip systems in British Columbia which are cooler places than Idaho and many places in Washington. Various fruit quality attributes such as fruit color, soluble solids concentration (SSC), size, and maturity can be affected by methods of irrigation and
levels of N application. Production of Fuji apples with desirable quality attributes in todayn++?Ts competitive global market, is extremely important and challenging for the apple growers of the Pacific Northwest because most of their fruits are produced for export. A carefully balanced level of nutrients in the fruit and leaf tissues, particularly N, potassium (K) and calcium (Ca) is essential to have fruits with optimum quality and maturity. The balance of these nutrients is affected by the quantity and method of irrigation.and quantity of N application. The best example for the importance of an optimum balance between N and Ca has been reported. It has been reported that fruit color and firmness diminished while internal ethylene and respiration increased as rate of N application increased. Under this circumstance, growers postpone the harvest to gain better color while the excessive
ethylene and CO2 will lead to spoilage in storage. Information on the interactive effects of different levels of N fertigation and quantities and methods of irrigation on fruit quality in Fuji apples is lacking. Therefore, in this research, we will study the influence of different irrigation regimes in combination with various rates of N on different characteristics of apples, including tree growth, nutrient partitioning, fruit size, color, SSC, firmness, internal ethylene, respiration, and storage physiological disorders.