Vegetable consumption is a major source of micronutrients, vitamins and health-promoting compounds that mitigate diseases and malnutrition in humans. Despite the importance of tomato, poor soil fertility and crop nutrition coupled with various pests and diseases limit both the quantity and quality of tomato produced. Tomato early blight (Alternaria solani) or late blight (Phythophthora infestans) and Fusarium Wilt (Fusarium oxysporum) often cause plant death and yield loss. Meanwhile, mole cricket (Gryllotalpa africana spp.) are critical pests at early seedling growth after transplanting that cause damage via feeding on roots or stems/leaves, and through their tunneling behaviour in rhizosphere. In addition, herbivorous feeding by mole cricket on stems/leaves increases the probability of introducing plant pathogens to seedlings, since some insects serve as vectors.
Various management practices including the use of bio-control agents have been employed to control mole cricket. Combinations of synthetic pesticides, fungicides and inorganic fertilizers are commonly used to control tomato pests/diseases and boost plant nutrition/growth. However, the pesticides, fungicides and fertilizers are scarce and expensive for smallholder farmers in Sub-Saharan Africa (SSA), coupled with potential negative externalities. Hence, there is increasing need for sustainable alternatives that are environmentally safe, readily available, affordable and adapted to the specific needs of smallholder farmers in SSA. Meanwhile, some botanicals such as Neem, Piper and Moringa have demonstrated comparable efficacy with synthetic pesticides and fungicides for mitigating crop pests and diseases, with less negative environmental effects. Some plant biomasses have dual-properties for simultaneously improving plant nutrition and protection, such as Mucuna spp and Tithonia diversifolia. Tithonia biomass demonstrated strong potential to rejuvenate soils while mitigating pests and diseases. Similarly, Mucuna biomass influenced soil microbes and suppressed nematodes. Correspondingly, Piper guineense seed extracts demonstrated strong potential for mitigating insect pests and diseases. In addition, a combination of T. Diversifolia, P. Guineense and Oil Palm Bunch Ash served both as insecticide and fertilizer, which decreased sweet potato weevil damage and increased yield.
The objective of this study was to enhance tomato protection and yield via sustainable integrated soil fertility management by using a locally produced dual-purpose organic amendment that is adapted to the specific needs of farmers. Thereby, simultaneously mitigating tomato pests and diseases while improving soil fertility and plant nutrition, which stimulates crop growth and enhance yield. Therefore, compared to treatments that combine synthetic pesticide and inorganic fertilizer inputs, it was hypothesized that locally produced dual-purpose organic amendment (i) will effectively mitigate tomato seedling damage by mole cricket, (ii) will reduce disease incidence and (iii) enhance tomato nutrition and yield.
I conducted an investigation at Moli-Buea in Southwest Cameroon.The soil is derived from weathered volcanic rocks dominated by 51.6% silt, 42% clay and 6.4% sand. Buea has a mono-modal rainfall regime with less pronounced dry season and 85-90% relative humidity. Heavy rainfall occurs between June and October while the dry season starts from November to May with 2085-9086 mm mean annual rainfall between March and November. The mean monthly air temperature ranges between 19°C and 30°C, while soil temperature at 10 cm depth decreases from 25°C to 15°C with increasing elevation from 200 m to 2200 m above sea level. The experiment was conducted between December 2015 and February 2016, and setup as a randomized complete block with three treatments (organic, inorganic and control) and four replicates each comprised of two outlets at the top. One outlet was fitted with an outlet pipe firmly attached with plastic around it that prevents air from entering into the digester and the other end of the pipe was dipped into a 10 L water-filled jar for anaerobic respiration and gaseous exchanges. The other outlet was tightly locked with a removable cork and used for stirring the content of the digester regularly to enhance the digestion process. The production of dual-purpose organic amendment started on November 3, 2015 when the digester was filled with 100 L fresh spring water. The following materials were added to the digester; 25 kg sunflower (Tithonia diversifolia) leaves and stems, 25 kg (leaves, stems, cobs and seeds) of the cover-crop (Mucuna cochinchinensis), 25 kg cow dung, 25 kg fresh sugarcane stems (Saccharum officinarum), 0.5 kg fresh cow milk, 1 kg garlic (Allium sativum), 1 kg onion (Allium cepa L.) and 1 kg ginger (Zingiber officinale L.). Mucuna and Tithonia were added to improve plant nutrition and protection. Ginger, onion and garlic were supplemented due to their insecticidal and fungicidal properties. Fresh cow milk was added in order to enrich the digester and facilitate fermentation via enhanced microbial activity. The fresh sugarcane served as glucose source for enhanced microbial activity and fermentation. Cow dung was added in order to enrich the content with macronutrients, improve microbial activity and facilitate fermentation.
The content of the digester was fermented for sixteen weeks at local air temperature, and stirred every three days with a wooden stick, to ensure homogeneity and enhanced fermentation. All materials used in the production process were thoroughly washed with fresh spring water and sterilized with a local chlorine detergent (Eaux de Javel). The dual-purpose organic amendment effectively protected tomato seedlings from mole cricket damage during the entire experimental period with no recorded seedling damage.
It is not economically sustainable to produce tomatoes in the study area without external fertilizer inputs. The locally produced dual-purpose organic amendment demonstrated efficacy as a viable sustainable alternative to mitigate tomato seedling damage by mole crickets and improve tomato performance. In addition, it stimulated the growth of young tomato seedlings beyond the plant size that can easily be damaged by mole crickets. The accessibility of raw materials, simplicity of the technology and low cost of production, coupled with the dual-properties for improving crop protection and plant nutrition makes the organic amendment a sustainable alternative for use over synthetic pesticides and inorganic fertilizers for controlling tomato pests and diseases while improving soil fertility and crop nutrition. The locally produced dual-purpose organic amendment is adapted to the specific needs of smallholder farmers for integrated soil fertility management. Hence, it is an economically viable option for improving tomato protection and performance without jeopardizing human health and environmental sustainability. That’s the way to preserve our agricultural identity and integrity, that’s the future of Africa.
Gwangwa’a Priestley Pride Tabi, Cameroon