Zonal Salinization of the Root System in Relation to Plant Growth

Corn and tomatoes were grown in the greenhouses in boxes containing three horizontal soil zones with a layer of coarse quartz sand to separate the zones. Either fresh or saline waters were supplied to each soil zone through porous ceramic tubes to maintain a fairly uniform water suction in each zone. Introduction of saline water into a given zone caused the uptake of water by the plant from that zone to decrease as soil salinity increased to a critical value, at which point water uptake ceased. The amount of water taken up by the plant from the nonsaline zones increased so that the total amount of water taken up by the plants was slightly less where one‐third of the soil was salinized as compared with the nonsalinized treatment. Water uptake further decreased where two‐thirds of the root system was salinized. Plant growth was unaffected when one–third of the root system was salinized, and yields were only slightly decreased when two‐thirds of the root system was salinized. Excessive salinization of the surface soil did not affect water uptake. Water uptake by tomatoes was more affected by zonal salinization than was corn.