Crop Protection & Environmental Biology

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    Physiological responses of cowpea simultaneously exposed to water deficit stress and varying light intensities at vegetative and reproductive growth stages
    (Update Publishing House, 2022) Adeniyi, O. I.; Adejumo, S. A.; Fofana, M.; Adegbehingbe, F. T.
    A combination of stresses as it occurs on the field poses more challenges to crop production than individual stress. Crops’ response to single stress also differs from that of combined stresses. The morpho-physiological responses of two cowpea varieties (IT89KD-288 and IT99K573-1-1) to a combination of stresses (water deficit stress and high light intensity) were investigated at different growth stages. Three levels of light intensities (L3: 259 Lux- 36%, L2: 394 Lux-55% and L1: 710.2 Lux-100%) were imposed using one, two and zero layer(s) of the net, respectively, while, water deficit stress at four levels (W1: no water stress; 0-5 bars, W2: moderate water stress; 5-15 bars, W3: moderately-severe; 15-40 bars and W4: severe water stress; 40-70 bars) was imposed differently at vegetative and reproductive growth stages. Data were collected on the cowpea yield, Leaf Temperature (LT), Chlorophyll (C), Photosynthesis (P), Stomatal Conductance (SC) and Canopy Transpiration Rate (CTR). Exposure to W4 under L1 considerably reduced cowpea yield by 80% compared to those grown under L3 and full watering. Reduced light intensity enhanced cowpea grain yield irrespective of water deficit stress and IT89KD-288 was superior to IT99K573-1-1. Reduction in light intensity also increased the SC from 55.18 in L1 to 76.88 in 36 % L3. Full light intensity without water stress (100% light intensity), increased C content, while severe water stress reduced the C content and CTR. Photosynthesis was, however, reduced under low light intensity compared to 100% light intensity. It was also observed that water deficit stress imposed at the reproductive stage did not affect P, CTR and SC unlike that of the vegetative stage. In conclusion, reduced light intensity enhanced cowpea tolerance to water deficit and increased yield. Cowpea response was dependent on growth stage, variety and severity of stress.
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    Ameliorative roles of compost on okra (Abelmoschus esculentus L.) exposed to drought stress at vegetative and reproductive growth stages
    (Society of Land Measurements and Cadastre from Transylvania - SMTCT, 2020) Ezeh, O. S.; Adejumo, S. A.
    Okra growth and yield are adversely affected by drought at different growth stages. This is aggravated by poor soil fertility. In this study, the roles of compost applied at 0, 5 and 10 t/ha on the tolerance and morphophysiological response of okra (NHAe 47-4) exposed to varying levels of water stress (25%, 50%, 75% and 100% field capacity, FC), at different growth stages (vegetative, reproductive and vegetative-reproductive stages) for ten days duration were assessed. Data were collected on okra growth and yield, leaf relative water content (LRWC), leaf photosynthetic pigments (LPG) and proline accumulation. Results showed that drought stress reduced LRWC, LPG, growth and yield of Okra. This reduction was more evident in okra plants exposed to severe stress for 10 days and at the reproductive stage. Soil amendment with compost however, had cushioning effect on drought stressed okra. Compared to control, it increased the LRWC, LPG, growth and yield of okra. The ameliorative roles of compost were however, dependent on stress intensity, compost dosage, okra growth stage and stress duration. Though, okra plants stressed at 25% FC were more affected by drought stress, but compared to the un-amended soil, those grown on amended soil were more tolerant. Higher compost rate was superior to lower rates. Whereas, higher proline accumulation was recorded in plant exposed to 25% field capacity without amendment, proline accumulation was reduced in the plants grown on compost amended soil and exposed to drought which was an indication of stress reduction. Generally, okra stressed at vegetative growth stage only was able to recover rapidly and had better yield compared to those stressed at reproductive growth stage. It is concluded that addition of compost to soil could reduce the drought stress effect on okra.
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    Morpho-physiological responses of cowpea to different time and rates of compost application under water stress
    (Faculty of Agriculture and Forestry, University of Ibadan, 2017) Adejumo, S. A.; Orimolade, D. A.; Olaniyan, B. O
    Drought and poor soil fertility constitute serious threats to crop production. Water stress reduces crop yield by about 80%. In this study, the effect of Mexican sunflower compost on the morpho-physiological and biochemical responses of cowpea under water stress (100, 50 and 25% field capacity) was investigated. Compost was applied at different rates (10:C1 and 15 t/ha: C2) and at different times (two weeks before (B) and after (A) planting of cowpea seeds as well as repeated application (BA) during one cropping season. Data were collected on growth and yield parameters, chlorophyll and carotenoid content and stomata density. The results showed that although water stress adversely affected cowpea growth and development, soil amendment with compost increased the growth and yield parameters of cowpea. Variations were however observed in the performance of plants treated with compost based on different rates and time of application under different water stress regimes. Application before seed sowing and repeated application after seed sowing resulted in better plant performance compared to the application after seed sowing alone. Cowpea plants grown on soil amended with the higher rate (15t/ha) of compost both before and after seed sowing (C2B+C2A) also showed superiority in all the parameters considered. Cowpea dry matter yields were increased by 98, 110, 153 and 223 % in C1B+C1A, C1B+C2A, C2B+C1A and C2B+C2A compared with control (P<0.05). Chlorophyll content, carotenoid content, and stomata density of cowpea under water stress were also enhanced with compost application. Application of compost both before and after seed sowing enhanced cowpea growth and yield under water stress.