B. Bar‐Yosef  

B. Sagiv

The objective of the study was to relate tomato fruit yield and N uptake to water application rates via a trickle irrigation system at given N rates and to total water potential in the soil root volume. This information is needed to improve tomato cropping management under point source irrigation. The experiments were conducted on sandy soils at three different locations in Israel and included combinations of several daily N and water application rates, and two irrigation intervals. Fruit yield responded linearity to increasing total irrigation rates (Q_w) up to 80% of the accumulated evaporation from a U.S. Class A pan (E_p), the slope of the response line being 15 metric tons/ha for each 10% change in Q_w/E_p. The optimum average N concentration in the irrigation solution was determined to be 130 ppm N, below which yields and growth were inhibited and above which the soil water potential Ψ decreased, thus increasing the dry matter content of the fruit. A decrease in Ψ from −50 to −150 centibars appreciably decreased fresh fruit yield; a further decrease in Ψ caused a slower decrease in fresh fruit yield.