Soil Water-Holding Capacity

Soils must be able to retain moisture for plant growth. Soil moisture should be available to the plants. Soils must be sufficiently moist and aerated (not waterlogged) to maintain photosynthesis and transpiration and to enable the uptake of nutrients by the plants.

Maintaining adequate soil moisture content during the growing season is critical to nutrient use efficiency. Soils with moisture deficiency such as sandy soils show a low water-holding capacity and high evaporation. The goal of soil moisture management is to maximize the intake of rainwater into the soil and to maintain the soil moisture content at near field capacity as long as possible during the growing season.

To maintain soil water content following strategies are used:

1. Planting a cover crop to slow runoff
   Mulching with crop residues or plastic sheets to slow runoff and reduce evaporation losses. It can also prevent crop drought stress during dry spells in the subhumid regions, especially during the early stage of crop growth.
   Using no-tillage with a crop residue mulch on medium to coarse-textured soils improves rainwater infiltration and reduces evaporation.
2. Early sowing at the onset of the rainy season to optimize soil moisture use.
3. Adjusting planting density to optimize soil moisture use.
4. Relay cropping ad intercropping helps maximizing water use by crops during the rainy season.
5. Runoff harvesting and microcatchments improves soil moisture storage during the cropping season.
6. On crusted and compacted soils, light tillage using a hand hoe or chisel plow helps improving rainwater infiltration into the soil.
7. Planting tree or grass barriers along contour bunds and terraces can reduce runoff and soil erosion in slopes.
8. Leucaena (Leucaena leucocephala), a fast growing leguminous tree and Vetiver (Vetiveria spp.), a deep rooting grass are widely promoted species for soil and water conservation on sloping lands in humid and subhumid regions.