Dr. Koon-Hui Wang shows community participants how to improve soil health at a recent field day.

The humble soil’s status has undergone a dramatic shift in recent years. Once it was considered little more than a physical matrix, providing a place for roots to develop— the bulk of the plant’s needs were thought to come from external applications of chemical fertilizer and water, and its defenses from chemical pesticides.

However, yield declines after growing the same crops on the same fields, with few or no rotations, caused many farmers and researchers to reconsider. They found that these declines were often caused by a combination of soil problems: nutrient imbalances, salt accumulation from years of chemical fertilizer, compaction, and opportunistic soil pests and diseases fostered by monoculture planting and extensive soil-disturbing tillage.

Dr. Hector Valenzuela has worked with both home growers and ag professionals.

Building and maintaining soil health and quality can help to tackle all these issues. The soil is now recognized as an entire biome, with a biodiversity of microbes and fauna rivaling the diversity of plant and animal life in the Amazon! Its rich biological life facilitates synergistic ecological functions, resulting in better water and nutrient relations as well as improved internal mechanisms of biological pest control.

Hector Valenzuela and Koon-Hui Wang of the Department of Plant and Environmental Protection Sciences are helping growers improve the quality of their soil—and their crops. Dr. Valenzuela, who established the state’s first organic research plots in 1993, has given many lectures, presentations, and workshops, and much hands-on help, concerning soil quality, preparation, and regeneration; bioremediation; soil and water management; agroecology; and sustainability. He’s worked with both home growers and ag professionals to improve crop viability and nutrition, including a six-year “home-gardening” project in M¯anoa Valley to grow specialty crops with minimal external inputs, and a project helping farmers on the Kohala Coast to use improved irrigation practices and cover-cropping to build soil quality and increase the phytochemical content of medicinal herbs.

Cover-cropping is also an important facet of Dr. Wang’s research and outreach programs. Cover crops prevent soil erosion, reduce nutrient leaching, add organic matter, improve soil health, and suppress plant-parasitic nematodes and weeds. They can also reduce foliar insect pests and pathogens, while leguminous cover crops can contribute significant nitrogen to the soil. Dr. Wang’s numerous field days, workshops, publications, and presentations describe how best to practice conservation cover cropping in Hawai‘i. At root, the work of both centers around a basic theme: healthy soil makes for healthy plants—and more sustainable planting systems.