Soil texture and soil structure are unique soil features that significantly impact soil behaviour, such as water holding capacity, nutrient retention and delivery, drainage, and nutrient leaching.
According to a water resource management researcher at the Agricultural Research Council (ARC), Melvin Nyathi, soil fertility, and coarser soils have a lower ability to hold and keep nutrients than finer soils. However, in moist settings, fine-textured soils experience severe leaching.
How is soil texture defined?
Soil texture refers to the amount of sand, silt, and clay sized particles in the mineral fraction of soils. Clay soils are very fine, while sandy soils are the coarsest. Loam soil is a mix of sand, silt, and clay that shows the characteristics of each.
“Soil texture will be the proportion of sand, silt, and clay content, because they play an important role in making the soil texture, at least it should be 40% sand, 40% silt, and 20% clay,” he explains.
Sandy soils have bigger particles because they are more permeable. Crops will not grow successfully if there is too much sand. Adding organic matter to the soil is one approach to improve this. It will improve the texture and structure of sandy soils.
“If the soil consists of too much clay, you should do the opposite and include coarse material, such as sand or grit, so that both ways can improve soil texture,” he explains.
The benefits of improving soil texture
Because plants require water to flourish, soil texture is important. When you water or drain the soil, too much clay might make it difficult for water to enter or exit. Too much sand might cause water to evaporate too quickly. It all comes down to finding the appropriate balance for your plants.
“A good amount of sand, clay, and silt is essential for water retention. So having a healthy soil texture [will ensure] that your plants have a proper water balance. It will also efficiently transfer nutrients, allowing the plants to thrive,” he explains.
Using animal manure
Manure can be used to improve the soil. When you put it in the soil, it improves the soil. However, some plants contain small animals in the soil that are harmful to them.
“Use [organic matter] that bind and improve soil structure. Another benefit of animal dung is that it reduces soil bulk density, which reduces [compaction],” Nyathi shares.
Water from irrigation will sink into the soil more effectively if the soil is not compacted. This is a significant benefit of having a healthy soil structure.
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The role of water in soil maintenance
Soil formation occurs through processes in which rocks rip off, which can take several years. However, when it comes to soil formation, water will play a significant role in tearing the rock bit by bit. It will transfer the dirt to a flat area over time, which is excellent because this normally happens on a mountain, and is good for the soil and crop growth.
According to Nyathi, when you irrigate and have well-structured soil, water becomes readily available. It’s usually best to irrigate up to the field’s capacity. This ensures that plants can breathe well during the fertilisation process, leading to optimal conditions and reducing stress, ultimately resulting in good yields.
Soil structure can improve and repair itself
There are many soil cultivation strategies, such as varied tillage methods. You can utilise direct drilling, minimum tillage, or full tillage, each with its own method of working the soil.
“Rather than the existing farming practices, minimal or no tillage promotes soil structure because it is not disturbed. That’s one way they can put it to use,” he explains.
Adding organic matter to cover crops in your soil will improve the soil texture or structure. Organic matter, such as;
- solid manures
- liquid manures
- plants or crop residues
Crop rotation is another useful method. For example, if you’ve been producing maize for three years and see a reduction in soil structure, try planting beans next. Beans add nitrogen to the soil, improving both soil health and texture. Following this, reverting to maize can be more successful, especially if the planting is done correctly, contributing to further improvements in soil texture.
“Agroforestry, a combination of crops and trees, will help improve soil texture too. On the other hand precision farming, known as a farming management concept based on observing, measuring and responding to inter- and intra-field variability in crops makes use of satellites and digitalised machines that help a farmer to gain knowledge of where to add organic matter and where it is not needed,” he explains.
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