Transpiration Effects on Leaching Fractions
1977
Meiri, A. | Kamburov, Josephine | Shalhevet, J.
Water uptake by plants during the processes of infiltration and redistribution may introduce considerable errors in actual leaching when calculations are based on pre-irrigation soil water deficit. The objective of the study reported here was to measure and demonstrate the importance of this water uptake in causing a reduction in the actual leaching. Experiments were conducted with sunflower plants (Helianthus annus L.) using containers with screen bottoms which drained into dry soil. The soil below the container was changed before each irrigation. Both saline (32 meq/liter NaCl + 16 meq/liter CaCl₂) and non-saline water were used at six leaching fractions (0.1 to 0.4). Drainage was doubled when plants were covered with plastic bags to suppress transpiration. Water uptake during leaching reduced the intended leaching fraction by 51 and 42% in the non-saline and saline treatments, respectively (mean for all treatments). Measured chloride content in the containers was similar to that calculated from salt balance. The chloride concentration in the highly leached top soil indicated a 20% water uptake during flow. The results indicate that calculations of water application depth for leaching should not be based on soil moisture deficit but on the actual evapotranspiration of the crop. This is particularly true, for high frequency irrigations and for high transpiration rates.
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