Physio-Morphological Traits Contributing to Genotypic Differences in Nitrogen Use Efficiency of Leafy Vegetable Species under Hydroponics

Abstract

Soil fertility is declining in low-input agriculture due to insufficient fertilizer application by small-scale farmers. On the other hand, the concerns are rising on environmental pollution of both air and water in high-input agriculture due to excessive use of N fertilizer in a short growing season of vegetable crops, which is directly linked with the health of human beings and environmental safety. The aim of the study was to determine genotypic differences in Nitrogen Use Efficiency (NUE) of different leafy vegetable species (Arugula, Spinach, Cress, Parsley and Dill) grown hydroponically under two different N-rates (Low N: 0.3 mM and High N: 3.0 mM) and to identify the plant traits which are contributing to NUE. The nutrient solution experiment was conducted between March – April in 2020 by using an aerated Deep-Water Culture (DWC) technique in a fully automated climate room with a completely randomized block design (CRBD) with three replications for five weeks. The results indicated that shoot growth, root morphological and leaf physiological responses were significantly (p<0.001) affected by Genotype, N-Rate and Genotype x N-Rate interaction. Shoot growth of some vegetable species (Argula, Spinach and Cress) was significantly higher under low N than high N-rate, illustrating that they have a great capability for NUE under low N stress conditions. Similar results were also recorded for the root growth of the N-efficient species under low N-rate. The NUE of these species was closely associated with leaf physiological (leaf area, SPAD, photosynthesis, leaf chlorophyll (a+b) and carotenoid) and root morphological (root length, root volume and average rot diameter) characteristics. These physiological and morphological plant traits could be useful characters for the selection and breeding of ‘N-efficient’ leafy vegetable species for sustainable agriculture in the future. However, further investigation should be carried out at field level to confirm their commercial production.