Building Soil Quality to Reduce Drought Stress
Joseph R. Heckman, Ph.D., Soil Fertility, Rutgers
[Editors Note: This article, though directed to commercial growers and farmers, applies equally to the home garden. Certain techniques would be modified to the scale of gardens and equipment available.]

The amount of drought stress exhibited by crops is not entirely due to lack of rainfall. The degree of wilting or leaf rolling expressed over a field during a drought is often a reflection of differences in soil type and soil quality. Symptoms of drought stress are partly related to soil properties that influence the ability of soils to absorb rainfall, store water, and deliver it to the growing crop. Soils that are sandy or shallow are inherently drought prone whereas deep loamy soils are better able to sustain crops through a drought. Soil physical properties such as texture cannot be easily changed, but soil quality can nearly always be improved with good soil management. Soil quality (sometimes referred to as soil health) is the capacity of a soil to function as medium for plant growth.

Attention to the soil management practices listed below can lead to enhanced soil quality and enable crops to better withstand drought.

  1. Adopting cultural practices that build and maintain soil organic matter content are key to building soil quality. Things you can do to increase soil organic matter content:
    ~ Grow sod crops in rotation with grain crops.
    ~ Grow cover crops. Refer to Rutgers Cooperative Extension Fact Sheet FS 849 "Cover Crops and Green Manure Crops, Benefits, Selection and use." [good general information and a helpful chart of plants, seeding rates, etc.]
    ~Add organic matter to soil in the form of livestock manures, municipal shade tree leaves, and compost.
    ~Control erosion. Soil erosion must be controlled to keep top soil rich in organic matter in place. Leave crop residues on the soil surface to control erosion. [use mulch]
  2. Soil fertility impacts plant water relations. Things you can do:
    ~ Maintain soil pH in the desired range for the crops being grown. Allowing soil acidity to develop to the point where root growth is inhibited limits the volume of soil that can be explored for moisture. A regular soil testing and liming program helps to ensure that roots will be able to explore the entire soil profile for available water.
    ~ Potassium nutrition is closely linked to plant water relations. Optimum levels of potassium supplied in the soil improve crop tolerance to drought stress.
  3. Soil compaction destroys good soil structure and restricts root growth. Things you can do to avoid or correct problems related to soil compaction:
    ~ Avoid driving farm equipment over wet soils.
    ~Avoid tillage operations when soils are too wet.
    ~Examine soil profiles for hard layers that are restricting root growth. Perform deep tillage with a subsoiler to break up a hard pan. The soil must be sufficiently dry for the subsoiling operation to cause shattering of the compacted layer. [Double dig gardens, if possible.]
    ~Leave crop residues on [or mulch] the soil surface to encourage earthworm activity. Earthworm channels improve rainwater infiltration and root development.

Droughts occur for varied durations during most growing seasons. Through good soil management practices, growers can help sustain crop growth during periods of low rainfall.