DYNAMICS OF WATER AND NUTRIENT USE, STRESS DEVELOPMENT AND YIELD OF Corchorus olitorus Linn.

Abstract

The need to remove more water in agricultural production, without limiting crop growth and yield, has led to the development of crop models. This makes more water available for domestic and industrial uses. Studies on water and nutrient use efficiencies have been reported but there is dearth of precision agriculture information on Corchorus olitorus. The study was designed to investigate the effects of water and nutrient use on the growth and yield of Corchorus olitorus. Field and greenhouse studies were conducted at the University of Ibadan. Plot size (1m2 ) with three replications were used for planting Corchorus olitorus seeds at 30 cm x 10 cm with planting rate of 300,000 stands/ha. At greenhouse, 1 plant/pot containing 5 kg soil was used. Soil samples were collected at 0-30 cm depth for soil textural classification. Four irrigation treatments of 2, 4, 6, and 8 mm of water were applied at 2-day interval for 10 weeks coupled with NPK 15-15-15 fertilizer application at a rate of 100, 200, 300 and 400 kg/ha. Experimental design was split plot for field trial and completely randomised for greenhouse trial. Yield, Crop Growth Coefficient (Kc) for 8 weeks using field trial and CropWAT model, Actual Evapotranspiration (ETa) and Growing Degree Days (GDD) were obtained using standard methods. Data on Water Use Efficiency (WUE), Fertilizer Use Efficiency (FUE) and Stress Tolerance Index (STI) were evaluated. Empirical crop growth models were developed. Data were analysed using ANOVA at α0.05. Soil type was loamy sand. Yield (t/ha) at different irrigation treatments were 0.73±0.15 (2 mm), 1.27±0.12 (4 mm), 2.63±0.16 (6 mm), 3.53±0.57 (8 mm), and 1.33±0.21 (2 mm), 2.03±0.15 (4 mm), 4.23±0.50 (6 mm), 5.83±0.38 (8 mm) for field and greenhouse, respectively. Fertilizer application increased yield (t/ha) significantly to 0.93±0.11 (2 mm, 400 kg/ha), 1.47±0.12 (4 mm, 400 kg/ha), 2.97±0.45 (6 mm, 400 kg/ha), 5.07±0.35 (8 mm, 300 kg/ha), and 1.53±0.15 (2 mm, 400 kg/ha), 2.23±0.21 (4 mm, 200 kg/ha), 5.80±0.61 (6 mm, 400 kg/ha), 7.13±0.38 (8 mm, 100 kg/ha) for field and greenhouse, respectively. The Kc were 0.43, 0.44, 0.61, 0.81, 0.98, 0.89, 0.61, 0.61 for field trial compared to 0.44, 0.44, 0.57, 0.80, 0.92, 0.82, 0.67, 0.55 from CropWAT model. Cumulative weekly ETa of 2, 4, 6, 8 mm were 55.79, 103.46, 152.74 and 182.98 mm, respectively. Cumulative GDD ranges were 1311.80-1374.10 oC (greenhouse) and 1316.35-1397.20 oC (field). The WUE ranges were 0.08-0.15 (field), 0.12-0.27 (greenhouse), with 8 mm, 100 kg/ha (greenhouse) and 8 mm, 200 kg/ha (field) being the optimum. The FUE ranges were 0.05-0.21 and 0.11-0.25 for field and greenhouse, respectively. The STI were 0.067-0.461 and 0.088-0.649 for field and greenhouse, respectively; iii establishing water-stress impact on crop yield. At 8 mm irrigation treatment, fertilizer application of 100 and 300 kg/ha obtained maximum STI values for greenhouse and field trials, respectively. Empirical model to predict yield as affected by evapotranspiration was y=28.263x5 -69.51x4 +65.037x3 - 29.477x2 +7.1939x-0.0219. Irrigation treatments at 8mm had less water stress effect and improved yield. Water-stress, nutrient dynamics, crop growth and yield prediction model of Corchorus olitorus were established.