The aim of this research was to investigate the responses of Amaranthus cruentus L. to deficit irrigation under fertilization, in a 2 by 3 factorial experiment with two levels of irrigation (1.5 litre/week and 0.75 litre/week) corresponding to 2600 and 1300 mm/year respectively and three levels of NPK 20:10:10 (0, 138, 275 kg ha-1). This experiment was conducted in a screen house in Cameroon, and lasted for 12 weeks after the nursery phase. Growth parameters and chlorophyll fluorescence were measured weekly for 8 weeks. Destructive sampling was done at 12 WAT to determine biomass partitioning, water use efficiency and the root/shoot ratio. Data were analyzed for variance and relationships in the MINITAB Version 17 statistical package. Within each irrigation level, plant mass decreased as fertilizer rates decreased, while root: Shoot ratio increased instead. Plant mass expressed higher values at the higher irrigation levels while root: Shoot ratio was lower compared to that at lower irrigation levels. This shows a strategy for resource re-allocation to roots under both water and nutrient deficit. Harvest index was statistically similar across irrigation and fertilizer levels. Within the higher irrigation levels, WUE of plants decreased with a decrease in fertilizer rates but not for plants subjected to deficit irrigation. While chlorophyll fluorescence values differed significantly across treatments, all values were below 0.8, indicative of stress. Factor analysis showed that growth of A. cruentus was highly fertilizer-dependent, while chlorophyll fluorescence was irrigation-dependent. This suggest that fertilizer application is essential in ameliorating the effects of deficit irrigation, and will be essential in the production of this crop under deficit irrigation.

The need for production of high value crops has increased over the years, hence the need to more appropriately determine irrigation water levels in water-scarce scenarios. The Aim of this research was to 1) determine the effect of deficit irrigation on growth and yield of tomato, and 2) determine how poultry manure amendments of soil would interact with irrigation to influence the observed growth and yield responses. There were two irrigation levels namely 0.75 and 1.5 l per plant per week, combined with 0, 34 and 68 g/plant poultry manure, in a 2 x 3 factorial design with three replicates. Growth and yield parameters were measured till maturity. Data were analysed through RTANOVA in a GLM at α=0.05. Results showed that the combination of 0.75 l irrigation water per plant per week with 34 g poultry manure per plant significantly increased number of leaves, branches and collar diameter. At low levels of irrigation (0.75 l/plant/week) the highest number of flowers ( 196) is produced under fertilization with 68 g poultry manure per plant, with a reproductive success rate of 18.37%. When the irrigation rate doubles, the highest number of flowers (126 /plant) is produced in plants fertilized with 34 g/plant poultry manure, with a reproductive success rate of 42.06%., representing the best combination of treatments for maximum fruit yield; doubling manure rates to 68 g/plant results in increased flower abortion and reduced reproductive success.

With changing rainfall patterns, deforestation and degradation of arable land, freshwater resources for irrigation are reducing, increasing the potential for drought stress on crops. The aim of this research was to study the growth and ecophysiological responses of beans, pepper, tomato and watermelon potted and grown in screenhouse under varied irrigation, for 14 days. There were three treatments: zero irrigation after seedling establishment, 0.1 L/pot/week, 0.2 L/pot/week and 0.3 L/pot/week respectively, each pot with three plants, in a completely randomized design with 3 replicates. Growth and ecophysiological measurements were recorded for the first three weeks of growth. ANOVA and Pearson Correlation were conducted, with significance at α 0.05. Plants with zero irrigation had the least growth in all parameters measured; growth was stimulated by irrigation, with a threshold at 0.2 L/week (corresponding to 2200 mm, the mean annual rainfall for the region) for pepper, tomato and watermelon seedlings. Biomass accumulation in all species increased with irrigation but WUE decreased. The quantum efficiency of photosystem II photochemistry of beans and watermelon increased to 0.8 as irrigation increased, while pepper and tomato remained low in all treatments, indicating stress. These results show that early seedling stages are sensitive to drought; however, beans and watermelon seedlings were more resistant to soil moisture deficit than tomato and pepper seedlings. Early farm management should consider appropriate irrigation volumes for better and more vigorous crops in the field. This is essential in a future where irrigation water deficits are predicted to increase during the cropping seasons.

No abstract

Secondary salinization of arable lands, and declining irrigation water resources are major challenges for crop production. We investigated synergistic effects of salinity and irrigation on Phaseolus vulgaris L. in a 4 × 3 factorial experiment with four salinity levels (0, 4, 8 and 12 ppt) coupled with 3 irrigation regimes that reflected a deficit, normal and excess irrigation for the region. Growth and ecophysiological variables were measured, and data submitted to Analyses of variance, Correlation and Factor analyses in the Minitab Version 17 software. Salinity stress decreased height (35.05 to 31.97 cm) as salinity increased from 0 to 8 ppt. Number of leaves, number of branches, number of flowers and fruits as well as fruit mass and harvest index all decreased as salinity stress increased. Plants in the deficit irrigation regime had higher water use efficiency (1.27g/l) and transpiration use efficiency (29.51 g/l) compared to those under higher irrigation regimes. Salinity and water stress effects on yield and plant water relations would significantly impede production of this crop, with significant yield losses of over 400% in higher salinities. Therefore measures to alleviate soil salinity are necessary for enhanced P. vulgaris production in such saline contaminated areas.