Leaching fraction impacts water use efficiency and nutrient losses in maize crop under salt stress

Authors: FREITAS, EMANUEL - Universidade Federal Do Ceara (UFC); LACERDA, CLAUDIVAN - Universidade Federal Do Ceara (UFC); AMORIM, AILA - University Of International Integration Of Afro-Brazilian Lusophony (UNILAB); Ferreira, Jorge; COSTA, CARLOS - Universidade Federal Do Ceara (UFC); SILVA, ALEXSANDRO - Universidade Federal Do Ceara (UFC); GHEYI, HANS - Federal University Of Campina Grande

Submitted to: Revista Brasileira de Engenharia Agricola e Ambiental
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2022
Publication Date: 7/7/2022
Citation: Freitas, E.D., Lacerda, C.F., Amorim, A.V., Ferreira, J.F.S., Costa, C.A.G., Silva, A.O., Gheyi, H.R. 2022. Leaching fraction impacts water use efficiency and nutrient losses in maize crop under salt stress. Revista Brasileira de Engenharia Agricola e Ambiental. 26(11):797-806.

Interpretive Summary: Excessive accumulation of salts around plant root zones, mainly in arid and semiarid regions, lead to decreasing plant growth, crop yield, and may lead to death. Under excessive salinity, applying irrigation water in excess (leaching fraction, LF) to what is demanded by the action of evapotranspiration on plants is an efficient way to leach salts away from the root zone. However, excessive leaching may also lead to mineral nutrient losses and to poor water-use efficiency. This study evaluated water-use efficiency, maize leaf nutrient concentrations, and nutrient loss from soil when the LF was calculated by two different methods. The irrigation water salinities (ECw) used were 0.5, 2.0, 4.0, and 6.0 dS/m and the leaching fractions were established either according to a classic formula proposed by Rhoades or by applying a LF of 0.15 (15%) to the regular irrigation volume, calculated according to the soil water balance (SWB). Leaf concentrations of N, P, and K decreased according to increased salinity, regardless of LF. Adding a LF of 15% based on the SWB decreased soil mineral nutrient losses and increased water-use efficiency compared to the method of Rhoades. Our results indicate that a more accurate determination of LF is needed to increase economic returns in maize cultivation in semiarid regions, mainly when using low-quality saline water for irrigation.

Technical Abstract: Although leaching fraction (LF) is used to remove salts from the root zone under conditions of salinity, if miscalculated, it can decrease water use efficiency and lead to major losses of essential nutrients. This study evaluated the water use efficiency, leaf nutrient concentrations in maize plants, and nutrient losses as a function of two ways of determining the LF in maize crop grown in soil columns under salt stress. The experimental design used was completely randomized, with treatments arranged in split plots, with seven replicates. The plots were formed by two methods of determination of LF, and the subplots by four electrical conductivities of irrigation water – ECw (0.5, 2.0, 4.0, and 6.0 dS m-1). The leaching fractions were established according to 1) the formula proposed by Rhoades (RHO) and 2) by applying a LF of 0.15 calculated according to the soil water balance (SWB). The leaf concentrations of N, P, Ca, and Mg were higher in plants under SWB than under RHO method. The leaf concentrations of N, P, and K decreased with increased salinity, regardless of the LF. Adding a LF of 0.15 according to SWB resulted in decreased losses of nutrients and higher physical water productivity, as compared to the RHO. Thus, a more precise determination of the LF is needed to increase economic returns for maize cultivation in semi-arid regions when using brackish water for irrigation.