Nitrogen (N) fertilizer is commonly used to improve soil fertility and maize production in Cameroon, but high cost and potential environmental effects have necessitated site-specific N fertilization regimes that are adapted to particular soil and crop types. A field experiment was conducted with five N application rates (control–0, 50, 100, 150, and 200 kg N ha−1) to determine optimum rate for best maize yield with limited effect on soil acidification. The soil residual N ranged from 0.18 to 0.36% across N application rates and increased at higher application rates with the highest in 150 and 200 kg N ha−1. Soil C/N ratio ranged from 7.5 to 15.5 across N rates with the highest in control, which decreased at higher N application rates. Soil pH ranged from 4.7 to 5.4 across N rates, with the lowest in 200 kg N ha−1 rate. Maize grain yield and cob length ranged from 7.1 to 10.3 t ha−1 and from 14.5 to 18 cm across N rates, respectively, with the highest in 150 and 200 kg N ha−1. Maize 1000-grain weight ranged from 380 to 560 g across N application rates with the highest in 100, 150, and 200 kg N ha−1. Significant negative correlations occurred between soil pH and maize yield or 1000-grain weight. Maize N use efficiency decreased sharply at higher N application rates, as demonstrated by a strong negative correlation between the N-Partial Factor Productivity and total soil N. Overall, the lower soil pH at higher N application rates highlights the potential for deleterious effects of N fertilizer inputs on arable soils, which may eventually affect crop productivity, thereby suggesting lower N fertilization regimes between 50 and 100 kg N ha−1 as the optimum for maize production on the volcanic soils of Buea.
Bananas and plantains are important staple crops for many people in developing countries, but these crops are severely affected by biotic constraints that reduce productivity. A major biotic stress is the banana corm borer weevil (C. sordidus) whose larvae eat corm/pseudostem tissues that eventually weaken the plants and cause toppling. To manage these borer weevils, most farmers use synthetic pesticides with active ingredients from different pesticide groups. Over reliance and abusive use of pesticides result in detrimental effects on the environment and human health. These effects together with ecological backlashes such as development of resistance by the pest have led to numerous advocacies to minimize the use of these chemicals. To achieve this, there has been increasing number of researches to seek sustainable alternatives that could be used to replace these synthetic pesticides or be integrated with less toxic chemicals to effectively manage the pest. This review summarizes global research on the use of synthetic pesticides and alternative management techniques such as the use of appropriate cultural practices (e.g., clean planting materials, fallowing, mulching, intercropping, and trapping), botanical pesticides (e.g., from Solanaceae, Asteraceae, and Meliaceae), entomopathogens, predators/parasitoids, and the use of resistant crop varieties, as well as possibilities of engineering phytocystatins to produce transgenic varieties that will be harmful to weevil. The review ends with conclusions, limitations/gaps, and recommendations for future research for the different alternative options.
e impact of different land-use systems on some soil physicochemical properties and macrofauna abundance in the humid tropics of Cameroon was studied. e land-use types included secondary forest (SF), oil palm plantation (PP), banana plantation (BP), sugarcane plantation (SP), and rubber plantation (RP). Soil particle size distribution, bulk density (BD), pH, organic matter (OM), and number of macrofauna were evaluated. e results showed that OM and number of macrofauna were higher in the SF than in the other land-use types. Pearson's correlation analysis carried out to determine the relationship between OM and BD showed that OM and BD was strongly negatively related with correlation coefficient of −0.9653. It also showed a strong significant negative correlation between BD and ants population (r � −0.8828) and between soil pH and number of earthworms (r � −0.9072). Based on the results, the SF produced more organic matter and higher number of macrofauna. However, the OM of the other land uses was not low; hence, it could be beneficial to return plant residues to the field for maintaining soil quality.
Access to information on soil nutrients status and variability is essential in understanding the potential of soils and their responsiveness to management interventions in agriculture. The current study evaluated soil nutrients status in selected agroecological zones (AEZs) of Cameroon and identified variations and their adequacy for maize (Zea mays L.), sorghum (Sorghum bicolor L. (Moench)), and cassava (Manihot esculenta Crantz) production. A total of 163 soil samples were collected from surface (0–15 cm) layer for the determination of pH, organic matter (OM), estimated nitrogen release (ENR), sulphur (S), calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), boron (B), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), aluminium (Al), phosphorus (P), total exchangeable capacity (TEC), and base saturations. The results showed different degrees of variability in soil nutrients ranging from low to very high in all the AEZs. The soils in all the AEZs were consistently deficient in available phosphorus, sulphur, boron, and zinc in varying proportion and might be inadequate to supply cultivated maize, sorghum, and cassava with the nutrients needed to achieve optimal growth. The soils were also prone to Mg-induced K deficiency, which could limit the growth of maize, sorghum, or cassava. These results therefore suggest that management of inherent soil properties should be based on-site specific situations.
Soil fertility management of smallholder farms in the humid tropics is a major issue as a result of inherently low fertility with nitrogen being the most limiting plant nutrient. Use of grain legume fallows could improve soil quality through nitrogen fixation and ensure food and nutritional security in developing countries. This field trial was laid out in a Randomized Complete Block Design (RCBD) to evaluate the short-term benefits of grain legume fallows (common bean, groundnut, cowpea, and soybean) on soil fertility improvement and income generation in relation to a natural weed fallow system. The results showed that total soil nitrogen content ranged from 0.19-0.24%, and differed (P < 0.001) significantly with the highest in common bean plots as compared to the others. The soil organic carbon (SOC) content was highest in cowpea plots (3.36 %) and lowest in the natural weed fallow (2.77 %). However, the SOC were not significantly different among the fallow systems but were higher than the SOC of the soil before sowing (2.41 %). Grain yield ranged from 1.0-1.9 t/ha and differed (P < 0.001) significantly. The highest profitability of integrating grain legumes in farming systems was recorded in the groundnut fallow, followed by soybean, and bean. Cowpea generated a negative return, while the natural fallow system had no effect. Integrating grain legumes fallow into agricultural systems in the humid tropics enhance the value of the fallow lands and may serve as viable short-term economic incentives for smallholder farmers. Contribution/Originality:This study contributes to the existing literature that reports the benefits of grain legumes on soil fertility improvement and also showed that the integration of grain legume fallows into agricultural systems in the humid tropics generate income for smallholder farmers and could serve as motivation for their adoption.
The release of nutrients, including phosphorus from agricultural residues, is an important potential source of nutrients for subsequent crops. To fully understand the contribution of this residue P as a source of plant P for agricultural production, its chemical nature needs to be understood. In this study P species were identified and quantified in leaf litters and crops residues from cocoa farms, oil palm, rubber, and banana plantations by 31 P nuclear magnetic resonance (NMR) spectroscopy. Phosphorus in the crop residues was predominantly in the form of inorganic P mainly as orthophosphate and ranged from 45.9 to 89.2%. The highest relative percentage of P as orthophosphate was found in cocoa pod husk (89.2%) and the lowest percentage was found in decaying banana pseudostem (45.9%). Pyrophosphate was detected in trace amounts in all samples (less than 6%) except in fresh palm fronds. However, orthophosphate diester was detected only in fresh palm fronds (11.4%) and phytate was detected only in palm male inflorescence (6.7%). The result implied that cocoa pod husk, palm empty fruit bunch, and palm male inflorescence could be used as organic amendment, based on their high P content and release potential.
Treatment of yellow dye 23 by heterogeneous Fenton-like process was studied using iron rich soil as an iron source. The iron rich soil sample was characterized by XRD, SEM and BET analysis. XRD pattern indicates that the iron rich soil is made of goethite and hematite. The reaction was systematically investigated under various experimental conditions such as pH, iron rich soil dosage, oxidant and dye concentrations. The result revealed that using iron rich soil as catalyst led to high discoloration efficiency (97.71% for 140 min of treatment) at pH = 2.5, 2 g/L iron rich soil and 16 m•mol/L H 2 O 2. The degradation kinetics of acid yellow 23 can be described by a pseudo-first-order reaction following the Langmuir-Hinshelwood mechanism. The main roles of hydroxyl radicals in degradation process were investigated by adding of various radical scavengers.
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