Alternaria leaf spot of cabbage, caused by the Alternaria brassicicola, affects leaves of cabbages and often results in head rots causing severe decline in yield. In this work, the effects of systemic and combination fungicides on A. brassicicola mycelia growth in vitro and disease severity in field trials were investigated. The results of in vitro evaluation revealed that both fungicides significantly inhibited (p < 0.05) the growth of A. brassicicola under in vitro conditions. However, metalaxyl-M 6% was less effective with 100 μg/mL having only 30 ± 3.5% inhibition. On the other hand, 100 μg/mL of mancozeb 63% + carbendazim 12% had 94 ± 3.5% growth inhibition of A. brassicicola, respectively, under the same conditions. Dose-response analysis of the efficacy of the two fungicides showed that the LC₅₀ of metalaxyl-M 6% and mancozeb 63% + carbendazim 12% were 125.52 ppm and 57.22 ppm, respectively, indicating the superiority of combination fungicide over systemic fungicide alone. Field studies showed that while manure type significantly impacted on biomass production (p < 0.001), it did not significantly affect disease severity. On the other hand, the frequency of fungicide application impacted on disease severity, with biweekly application leading to a significant reduction in disease severity after 10 weeks.

Improving the fertility status of nutrient-depleted soils is critical to achieving food security. The negative effects of chemical fertilizers on soils necessitate the global quest for eco-friendly, effective, and sustainable alternatives. This work assessed the effect of black soldier fly (BSF) residue application on soil properties and watermelon growth. The study was set up in a completely randomized design with six replications. The treatments were BSF1 (BSF applied at 10 t ha⁻¹), BSF2 (20 t ha⁻¹), BSF3 (30 t ha⁻¹), and control. The plant data collected in this study were vine length, leaf width, number of leaves, and stem girth, and the soil’s physicochemical properties were determined. The results show that BSF residue-treated soils had 20.4–49.5% higher aggregate stability and 50–160% higher hydraulic conductivity than the control treatment. BSF residue-treated soils had significantly (p ≤ 0.05) higher pH, total N, available P, exchangeable K, and organic carbon than the control treatment. BSF3 treatment had the highest effect on available P and soil pH relative to other amended treatments. High rates of BSF residue application did not significantly increase the total available N and P contents, which could suggest that BSF application at 30 t ha⁻¹ may not pose a risk of N and P pollution to water systems. BSF residue-treated soils improved (p < 0.05) watermelon growth parameters relative to the control. Watermelon leaf length was significantly (p ≤ 0.05) longer for BSF residue-treated soils than the control treatment. A similar trend was observed for the number of leaves, leaf width, and stem girth. At 4, 6, and 10 weeks after sowing, BSF residue-treated plants had 38.2–104%, 22.7–118%, and 25.7–103% longer vine lengths than the control treatment, respectively. The study results suggest that BSF residue application can enhance the fertility status of a coarse-textured ultisol for watermelon production.

Organic farming ensures that crops are produced in a natural bio diversified state without loss of any productivity. Synthetic chemical usage in the tropics increases the levels of the environmental and health risks associated with agriculture. Every piece of synthetic material used each day by man to ‘improve’ agricultural productivity is either ‘polluting’ or ‘poisoning’ the environment. Through these damages to the natural environs by man, more deaths because of serious illness has been recorded. In this work, facts are presented and discussed on how intensive crop production causes problems and ways of ensuring less use of these toxic synthetic chemicals in crop production, especially in the tropical regions of the world. Furthermore, major benefits of organic farming in crop production as well as how organic farming ensures genetic diversity preservation are discussed. This review reveals how organic farming can reduce adverse environmental impact associated with conventional methods of synthetic chemical usage tradition. The work concludes that practising organic farming in the tropics would be very beneficial especially for future generations.

The study examined the effect of weed control practices and different fertilizer sources for the optimum growth and yield of bell pepper. The study was conducted at the teaching farm of the Department of Crop Science, University of Nigeria, Nsukka. The sample for the study were weed control practices comprising black polyethylene mulch, un-weeded plot, and manual weeding with hoe at 2-week intervals and different fertilizer types comprising cow dung, pig dung, and poultry manure at 20 t/ha, respectively; NPK fertilizer at 150 kg/ha; and no fertilizer (control). There were 15 treatment combinations arranged in a randomized complete block design (RCBD) replicated three times. The study revealed that the plots mulched with black polyethylene and poultry manure recorded a significantly higher number of leaves per plant (82.0), plant height (16.47 cm), a lower number of broadleaved weeds (1.45/0.5m2), grasses (1.50/0.5 m2), and sedges (0.70/0.5m2), weed dry weight (0.81 g), and higher weed control efficiency (86.48%). It concluded that applying black polyethylene mulch with the application of NPK or poultry manure provided positive results for growth as well as weed control and therefore should be recommended to the extension agents and farmers for efficient and profitable production of bell pepper.

Colocasia esculenta (taro), Ipomoea batatas (sweet potato), Abelmoschus esculentus (okra), Ananas cosmosus (pineapple), Musa paradisiaca (plantain), and Anacardium occidentale (cashew) are economically important horticultural crops in West Africa, which are widely grown across the region under rain fed conditions. They are very important set of crops that provides income for the individuals involved with it and thus contributing to economy of West African nation’s. For Predicting the potential future habitat suitability of these crops under different climate scenarios holds significance for their continuous cultivation and effective management. The Maxent model was used in this study to predict habitat suitability of these crops under current and future climatic conditions based on two representative concentration pathways (RCP4.5 and RCP8.5) for the years 2050s and 2070s. The data used were the occurrence records from Global Biodiversity Information Facility (GBIF) and WorldClim’s bioclimatic environmental predictor variables. The findings of this experiment showed that the habitat suitability of some crop species will =decrease and in some it will increase. Suitable habitat was predicted to decrease within the semi-arid and arid areas of the region, especially on those countries in northern part which includes Niger, Mali and Burkina Faso, as early as by 2070s. For species like okra, sweet potato and taro, there will be further decline as predicted under the higher emission scenario of RCP 8.5. The suitable habitat for cashew remained stable for future in all the models and scenarios used. This work provides the first theoretical guidance for possible future cultivation of these horticultural crops in the West Africa.