101 Questions answered
Why Soil Texture Matters for Lentil Growth: Water, Nutrients, and Drainage
Soil texture is a measure of how much clay, silt and sand is in a soil, and the amount of these largely affects a soils ability to store water and nutrients.
Sand has relatively coarse particles with large pore spaces, so water rapidly drains down the profile, often leaching organic matter and nutrients with it. Sand also has a low cation exchange capacity (CEC), around 1–4 cmol(+)/kg, meaning a lower ability to retain cations such as potassium, calcium and magnesium. Organic carbon is usually lower in a sandy soil, along with microorganisms, so the soil has a lower capacity to mineralise and supply nutrients.
Clay is much smaller than sand (<0.002 mm versus >0.05 mm), so it naturally has smaller pore spaces that can retain more moisture than a sand, both within the pores, but also between the clay sheets (platelets) that stack together. Some water can become tightly held in the small pores to the extent that plant roots cannot extract the water, i.e. the water is unavailable to plants. The graph below (right) illustrates how soil texture can affect plant available water.
Clays also have a higher cation exchange capacity than sands (10–40 cmol(+)/kg, depending on the type of clay), increasing their inherent fertility and ability to retain and supply vital plant nutrients. Because they are more fertile, clays often contain higher organic matter, which increases the anion-exchange capacity of the soil, meaning phosphorus is better retained and supplied too.
Sands typically have a clay content of <5% whereas loams have a clay content of 15–25%, meaning loams can hold more nutrients and water than sands.
Lentils don’t like acidic soil. Check if soil acidity is the reason the lentils aren’t happy. They also don’t like having wet feet, so if you have a duplex sandy soil with water that perches above the clayey subsoil, consider deep ripping to crack the interface and increase drainage.
