GREENHOUSE EXPERIMENT EVALUATION OF CONVENTIONAL DEFICIT IRRIGATION AND PARTIAL ROOTZONE DRYING UNDER VARYING WATER REGIMES WITH NITROGEN FERTILIZER ON SWEET CORN (Zea mays L. var saccharata)

Abstract

This study addresses the pressing challenges of water scarcity and nitrogen management in sweet corn cultivation within the Guinea savannah zone of Ghana. It investigated the influence of conventional deficit irrigation (DI) and partial root zone drying (PRD) techniques, along with varying water regimes and nitrogen fertilization, on the growth, yield, water productivity, and nitrogen use efficiency of sweet corn (Zea mays L. var saccharata). The experiment was carried out in a greenhouse from April to July 2023 at the Council for Scientific and Industrial Research-Savanna Agricultural Research Institute (CSIR-SARI), Nyankpala, near Tamale, Ghana. The experiment was a 3 x 3 x 2 split-plot design arranged in a randomized complete block design (RCBD) with three replications. The 18 treatment combinations include three deficit irrigation techniques (C-DI, A-PRD, F-PRD), three levels of water regimes (100%, 80%, and 60% ETc), and two levels of nitrogen (N) fertilizer (3.2 g/plant and 5.5 g/plant). CROPWAT model showed that the seasonal water needs for sweet corn ranged from 195.4 mm at 60% ETc to 325.6 mm at 100% ETc. The soil textural class was sandy loam, and the field capacity of the topsoil is 20.3 g. The result of the experiment showed that interactions of CI+100% ETc+N2 gave the highest (p > 0.05) shoot wet and dry mass, root wet and dry mass, total dry mass, and root N uptake. Shoot N uptake was the highest under this treatment and difference was significant. Kernel yield was highest (p < 0.05) with C1+100% ETc+N1. Water productivity in kernel yield was highest under interaction of C-DI+80% ETc+N1 but water saved did not maintain or improve yield. The interaction of F-PRD+60% ETc+N1 significantly gave the highest nitrogen use efficiency (NUE), but reduced the kernel yield by 74.5%. In conclusion, this study found that saving water through deficit irrigation did not result in the maintenance or improvement of sweet corn yields. The most effective approach for sweet corn cultivation in a greenhouse involves irrigating at full crop water requirement using a conventional method and applying the optimal fertilizer rate.