Guidelines for irrigation scheduling with skimmed groundwater to manage root zone salinity: a preliminary framework

In irrigated agricultural areas in semi-arid zones, where the canal water supplies are generally not sufficient to meet the crop water requirement, the necessity of pumped water application arises.If these irrigated agricultural areas are having shallow watertables, the salts are being added to the root zone: (i) from the bottom due to groundwater contribution and (ii) from the top due to pumped water and canal water applications.Under such irrigated agricultural conditions, there is a need of adopting practical ways and means for irrigation applications so that the root zone salinity is managed throughout the cropping season within the acceptable limits for good crop productivity.In this context, a set of guidelines for irrigation scheduling aimed at managing salinity in the root zone can provide such tools for irrigation applications.However, for developing and implementing guidelines for irrigation scheduling with skimmed groundwater, there is a need to develop linkages between the net soil moisture depletion and the threshold levels of the root zone salinity at different stages of the crop growth under different soil moisture depletion levels.Therefore, after reviewing the literature available on the factors concerning the salinity in the root zone, a preliminary framework for irrigation scheduling with skimmed groundwater is presented.The monitoring and evaluation of this preliminary framework will help in developing guidelines for irrigation scheduling with skimmed groundwater.The methodology of developing such guidelines is formulated so that it can be generalized for uses in other similar aquifers in the Indus Basin of Pakistan. Salt tolerance of cropsPlants differ widely in the their ability to grow and develop under saline and/or sodic conditions.The following parameters describes the impacts of soil and water salinity and/or sodicity on crop yield: