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Fertilization with K2SO4 resulted in good uptake of K by trees of French prune (Prunus domestica L. cv. Agen) whether K was applied in drip water or dry K2SO4 was placed on the soil under the emitter and then drip irrigated. These methods were much more effective than applying K2SO4 in trenches alongside the trees and then sprinkler-irrigating. K fertilization with a drip system resulted in K movement to depths of 60 to 75 cm, where the soil is wet from drip irrigation and roots are abundant, enhancing K uptake.

Five rates of urea-N each at two water levels (0.6 & 1.0 ETc) were applied to three varieties (Butte, Carmel, and NonPareil) of almonds [Prunus dulcis (Mil) D. A. Webb] planted in 1981 on a 3.65 × 5.47-m spacing (550 trees/ha) on Arbuckle gravelly loam (Fine-loamy, mixed, thermic Typic Haploxeralf). Trees were drip-irrigated to basins (three per tree) ≈7 cm deep and 30 cm in diameter, located 76 and 183 cm on either side of the trees in the tree row. N rates ranged from 0–57, 0–198, 0–454, 113–907, 170–1361, 227–1814, 227–1814, 170–1361, 113–907, 113–907, 113–907, 0–907, 0–907 and 0–907 g per tree, respectively, during 1982–1995 and were applied on a monthly basis in four to six increments beginning in April. Almond meat yields were >1500 kg·ha–1 in 1984 and as high as 3800 kg·ha–1 during the 12-year period for the 1.0 ETc water treatment and optimum N rate. Nitrogen response was generally in the 600–1000 kg·ha–1 range, with water treatment response in the 200–500 kg·ha–1 range. The three varieties generally responded to higher N and water rates in the order Butte > Carmel > NonPareil. Leaf analyses (three to six each year) were used to monitor treatment effects and evaluate need for other nutrients.