Agronomic measures are soil conservation techniques carried out as part of regular crop production activities. These include mulching, cover cropping, intercropping, fallowing, and adjusting planting patterns.
When applied appropriately, these practices improve surface cover, reduce the impact of rainfall, and limit the erosive forces of both water and wind. These practices are crucial for conserving soil health and enhancing agricultural productivity.
Mulching as a Soil Protection Method
Mulching involves placing a layer of material between the soil surface and the atmosphere. Mulch materials include residues from previous crops, grass, perennial shrubs, farmyard manure, compost, agro-industrial byproducts, inorganic materials, and synthetic products.
Mulching reduces rain splash impact, slows runoff, and lowers soil loss. Field trials across several Nigerian research stations have confirmed these benefits.
In Nigeria’s humid and semi-humid zones, adequate mulch material is usually available. However, in semi-arid regions, limited biomass production, bush burning, termite activities, and alternative uses of crop residues (like fodder or firewood) reduce the availability of mulching materials.
In such cases, brought-in organic mulch can be a solution. Generally, mulching is beneficial across Nigerian farming systems, especially for sandy or shallow soils, as it enhances moisture retention, soil fertility, and crop yield.
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Cover Cropping for Soil Erosion Control
Cover crops such as Pueraria phaseoloides, Mucuna pruriens, Centrosema pubescens, Stylosanthes guianensis, Phaseolus aconitifolius, and grasses like Pennisetum purpureum, Brachiaria ruziziensis, and Paspalum notatum grow quickly and form dense canopies. These canopies intercept raindrops, preventing soil particle detachment and reducing erosion.
Cover crops also improve infiltration rate, moisture retention, and reduce bulk density. Leguminous cover crops enrich the soil with nitrogen through biological fixation, increase cation exchange capacity, and boost yields.
Additionally, they suppress aggressive weeds like Imperata cylindrica and Striga hermonthica. However, vigorous cover crops may compete with food crops for growth resources. To manage this, compatible species should be selected and trimmed timely.
Improved Fallowing for Soil Recovery
Improved fallowing with selected herbaceous or tree species is vital in areas where traditional long fallows are no longer feasible. Grasses like Panicum maximum add organic matter to the soil. Shrubs such as Cajanus cajan improve physical soil properties by penetrating deep soil layers.
Leguminous fallows using Leucaena leucocephala, M. pruriens, or P. phaseoloides enhance nitrogen levels and improve phosphorus availability. Improved fallows also benefit soil microbial activity and nutrient cycling.
Multiple Cropping and Agroforestry Systems
Multiple cropping systems vary based on the spatial and temporal arrangement of crops. This traditional practice remains widespread in Nigeria. Agroforestry, a type of multiple cropping, combines woody perennials with crops or livestock.
Tree canopies and prunings enhance soil cover and serve as natural runoff barriers, especially when trees are planted along slopes.
Trees’ deep roots improve soil structure and infiltration, reducing runoff and erosion. In alley cropping, pruned materials add organic matter, and the system improves soil’s physical, chemical, and biological properties.
Despite its benefits, alley cropping faces challenges such as crop competition, pest risks, nutrient imbalance, and labour intensity. Due to these limitations, it may not be suitable for all Nigerian farmers.
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Intercropping for Enhanced Soil Protection
Intercropping, the planting of different annual crops in alternating rows, offers better soil cover than monocropping. A typical system in Nigeria is two rows of maize and two rows of soybean.
Research shows that intercropping cereals (Zea mays, Sorghum bicolor, Pennisetum glaucum) with legumes or root and tuber crops improves soil bulk density, increases nitrogen content, and stabilizes aggregates.
The inclusion of legumes enhances vegetation growth and reduces soil erodibility. Intercropping contributes to erosion control by increasing soil cover and reducing the erosive impact of raindrops.
It also boosts soil productivity and has been recommended as a reliable conservation method in tropical agriculture.
Planting Pattern, Plant Density, and Timing
Planting pattern, plant density, and timing play significant roles in reducing soil erosion. Closely spaced crops or crops planted during peak rainfall periods offer more canopy cover, shielding the soil from raindrop impact. Higher plant densities improve surface protection and reduce runoff.
Diverse agronomic soil conservation practices such as mulching, cover cropping, fallowing, multiple cropping, and appropriate planting patterns contribute significantly to soil protection.
These measures reduce erosion, improve soil physical, chemical, and biological properties, and enhance crop productivity.
Additional benefits include better weed control, reduced crop failure risk, and increased income through diversified production. The use of these methods is essential for promoting sustainable agriculture and improving the resilience of farming systems across Nigeria.
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