Managing topsoil means girding it for drought, rain

Hawaii weather predictions have been wild this year. El Nino patterns simultaneously project both hurricanes and drought across the state. How can the home gardener prepare for such extremes in both dry and wet weather? Borrow some techniques used by the Natural Resources Conservation Service and invest in your soil.

Beneath your feet lies a complex system of underground pores and channels, a combination of air pockets, minerals and organic matter capable of sustaining myriad species of organisms. Scientists refer to this as soil structure.

Home gardeners can manage soil structure to make it more resilient to both drought and tropical rain. By providing soil cover and increasing organic matter, you can see a difference in how your yard and garden respond to drought and heavy rain.

BELOW GROUND, add more organic matter. Farmers grow green manures, plants selected specifically to be grown and sacrificed by plowing them into the earth to provide nutrients, improve water-holding capacity and improve soil structure. The home gardener can mimic farmers and grow these same plants (such as sunn hemp or buckwheat) in the home garden and return them to the soil.

Another great option is to add lots of compost to the soil and work it in well. Don’t confuse compost with mulch — compost is the crumbly dark-colored earthy-smelling end product of controlled biological decomposition. Learn more about compost in “Hawaii Backyard Conservation,” available from the U.S. Department of Agriculture’s Natural Resources Conservation Service, Pacific Island Area.

ABOVE GROUND, keep soil covered. Don’t be complacent about bare dirt. Large heavy raindrops from our tropical storms are very damaging to soil (especially topsoil) and can easily dislodge and wash it away.

This suspended soil becomes sediment that damages our coral reef systems. A quick fix for the homeowner is to put down woody fibrous organic mulch on bare areas.

Organic mulches (derived from living materials) are also excellent for water conservation, as they retain moisture, reduce evaporation, cool the soil and reduce weed growth.

Mulch differs from compost because it has not been aged and decomposed. Chopped green waste (be sure it is free of weed seeds!) is great for protecting the soil surface. Find other suitable organic mulching materials in “Mulching for Healthier Landscape Plants” from the University of Hawaii’s College of Tropical Agriculture and Human Resources.

Why does adding organic matter work so well? The Natural Resources Conservation Service reports that organic matter holds 10 to 1,000 times more water and nutrients than the same amount of soil minerals.

Water infiltration increases and runoff decreases when soil structure improves. Surface structure becomes more stable and less prone to crusting and erosion.

Beneficial soil organisms become more numerous and active with higher levels of organic matter.

Providing soil cover on the surface conserves moisture, reduces temperature, intercepts raindrops (to reduce their destructive impact), suppresses weed growth and provides habitat for members of the soil food web that spend at least some of their time above ground.

This year is the International Year of Soils. Learn more about soil health at 808ne.ws/1UtHGJ4.

And prepare for wild weather. Invest in your soil.

Jody Smith is an education specialist in sustainable agriculture renewable resources for University of Hawaii’s College of Tropical Agriculture and Human Resources Cooperative Extension and a Certified UH Master Gardener on Oahu.