Response of soil and irrigated fruit trees to fertigation or broadcast application of nitrogen, phosphorus, and potassium

Traditionally, broadcast or foliar fertilizer applications have been used to improve or sustain the nutrition of many irrigated, deciduous fruit tree orchards in western North America. Recent developments, including adoption of low-pressure microirrigation systems and planting at higher densities [especially for apple (Malus domestica Borkh.)], have increased interest in controlled application of fertilizers directly with irrigation (fertigation). Recent fertigation research in western North America is reviewed, emphasizing results from high-density apple orchards. Fertigation and traditional broadcast application methods are examined with respect to mobility of N, P, and K in the soil and response of fruit trees to application of these nutrients.