Mar 132017

There are few annual crops where the farmer can recover costs of high fertilizer and soil amendment inputs required for desired yields coupled with disease and pests in this environment.

By Bruce Mathews.

Bruce Mathews

On January 9, the Hawaiʻi Island Food Alliance Food Access Working Group, together with The Food Basket, The Kohala Center, and the state Department of Health, hosted a presentation in Hilo by Ken Meter (president of the Cross-roads Resource Center, Minneapolis, Minnesota) that was entitled “Growing Secure Food Systems in Hawaiʻi”. The presentation focused on how the pre-European contact native Hawaiians were completely food independent and that the 1900s resulted in a downward spiral in food production in Hawaiʻi, which was particularly rapid from the 1940s onward. The mid 1960s was the last time that about half the food consumed in Hawaiʻi was produced here. The stated goal was to instigate change that results in greatly improved food independence on the Big Island. There was even quite a bit of discussion regarding community-based food systems and avoiding the cash-based economy, and doing food barter.

One of the major challenges was that there was no real discussion of the biophysical and social constraints that would need to be overcome. When I pointed out that Native Hawaiians largely farmed the fertile alluvial valley soils and sweet spot uplands where rainfall was sufficient to grow sweet potato, etc., but not so excessive to result in heavy nutrient losses (soil fertility depletion) by leaching I was told that one can use soil restorative rotations of certain (undefined) legumes to make the former sugarcane lands of the high rainfall Hilo-Hamakua Coast productive for food crops. I politely implied that this thinking was delusional and backed up by scientific evidence regarding the very limited potentials of biological uplift of nutrients and nitrogen-fixing green manures in high rainfall zones with heavily leached soils.

On the infertile upland soils in high rainfall zones the Native Hawaiians practiced slash and burn agriculture with short annual (usually one to two crop) cropping periods and very long fallows or plantings of tree crops such as breadfruit. Long fallows are not practical in the modern era. Neither is expansion of wetland and gulch taro production as most of the fallow areas are now zoned for conservation to protect wetland habitat and wildlife. In this regard it is interesting to note that the waterfowl of concern seemed to survive when Native Hawaiians and then immigrants from Asia cropped the valleys and gulches wall to wall with taro, had extensive aquaculture, and later also grew rice. Furthermore, it is problematic that most of the sweet spot uplands with high soil fertility that were formerly used largely for sweet potato cultivation are presently under the tropical grass pastures of the large privately held ranches. These lands are unlikely to be converted to row-cropped field systems and would require major irrigation infrastructure development to avoid the risk of crop failure during droughts that have become more frequent with climate change.

There is a reason that most of the former rain-fed sugarcane lands on the Big Island are now used for perennial pasture and tree crops that are not as nutrient demanding in terms of soil fertility as most annual agronomic and vegetable crops. In a large part it’s that there are few annual crops where the farmer can recover the costs of the high fertilizer and soil amendment inputs required for the desired yields coupled with the multitude of introduced disease and pest problems in this environment. To make matters worse, applied nitrogen and potassium fertility is rapidly leached away necessitating frequent reapplication. Due in part to the soil fertility constraints and cost of the available lands and labor we are not going to be growing staple crops in major quantities anytime soon.

Some keys to improving food independence are as follows: 1) developing viable strategies to recover essential plant nutrients from the human waste stream in order to reduce dependence on imported fertilizers, 2) designing novel controlled-release and extender fertilizers such as those based on colloidal ion exchangers (exchange fertilizer technology) for more efficient nutrient delivery in the humid tropics, 3) encouraging and facilitating state and federal professionals in horticulture and agronomy to conduct the scientifically non-glamorous but essential work of germplasm evaluation that includes crop nutrient use efficiency and pest-disease resistance parameters, 4) improving the opportunities for people interested in becoming farmers to have relevant training on commercial scale farming practices, and 5) educating people on the multifaceted components of successful rural entrepreneurship.

Bruce Mathews is dean of the College of Agriculture, Forestry and Natural Resource Management at UH Hilo. His areas of research are plant nutrient cycling and soil fertility; assessment of the impact of agricultural and forestry production practices on soil, coastal wetlands, and surface waters; and nutrient management practices for pastures, forests, and field crops in the tropics (learn more about his research). He received his bachelor of science in agriculture, with high honors, from UH Hilo in 1986. He received his master of science in agronomy from Louisiana State University and his doctor of philosophy in agronomy, with a minor in animal science, from the University of Florida. Contact.