Distribution of soil P and K as affected by NP-fertigation in high density apple orchards

Extractable soil P and K were monitored for three years at different depths and distances from irrigation emitters undergoing NP-fertigation in three different experimental high density apple plantings on loamy sand soils. Single dose application of P resulted in higher soil P compared to multiple applications of the same amount of P although such differences varied with distance and depth, declined after first year and were not measurable at mon than 60 cm from the emitter source. Extractable soil P increased with rate of fertigated-P and with drip-relative to microjet-fertigation. NP fertigation also reduced extractable soil K values over time with near deficient values measured near the emitter and soil surface by third year. Apple trees were more responsive to the changes in soil K than soil P status.