Human beings and even animals need to rest. But what about land?
“The effects of short-term land fallowing on soil quality and crop growth following the completion of this water transfer had not been studied in the region until recently. A study, funded by UA Technology and Research Initiative Fund, Water Sustainability Program, and conducted by Jeremy Cusimano for his UA master’s thesis, aims to quantify the effects of short-term fallowing on soil quality and agricultural productivity within the Palo Verde Valley. Working with local growers, the PVID, and the University of California Cooperative Extension in Blythe, the study examined differences in soil fertility, microbial communities, and crop growth and development between fallowed sites and cultivated sites throughout the Palo Verde Valley.
For the study, composite soil samples were systematically taken from numerous fallow and arable fields throughout the Valley. Soil samples were analyzed for plant-available nutrients, salt content and organic matter; while analyses of microbial functionality and diversity provided insight into biological shifts in the soils. The same fields were then planted in the fall with broccoli, which was used to compare the effects of fallowing on plant growth. Results revealed significant differences between fallow and arable fields in the Palo Verde Valley.
The study found that short-term fallowing had increased the quantity of carbon, or soil organic matter, and nitrogen,…the project also revealed that microbial communities in fallowed soils had significantly greater microbial diversity and functionality, indicating that microorganisms had benefitted from the period of rest. Such increased microbial diversity can lead to improved nutrient cycling and concomitant benefits to crop production. Lastly, improvements in soil quality associated with fallowing enhanced the growth and production of the fall broccoli crop. Marketable yield and total plant biomass were both significantly higher after fallowing, with fallowed fields producing on average an additional 30 cartons of broccoli per acre when compared with fields that had been continuously farmed.”
A nudge to fallow
*”An open letter by Cheryl Long (1999), the Senior Editor of Organic Gardening (Rodale Press), addressed to USDA Secretary Dan Glickman asked this very question. According to two studies mentioned in the letter, the vitamin and mineral content of American and British food appear to be declining. One study, titled “Nutrition Under Siege” (Jack, 1998), examined data published by the USDA ARS Nutrient Data Laboratory and concluded that a comparison of the data “show(s) a sharp decline in minerals, vitamins and other nutrients in many foods since the last comprehensive survey published over twenty years ago”, which was attributed to “a steady deterioration in soil, air, and water quality”. In a similar study (Mayer, 1997), Anne-Marie Mayer compared British data over a fifty year period and noted “significant reductions” in the levels of minerals in fruit and vegetables and questioned if modern agriculture could be responsible for the reduction. Long’s letter to the USDA expressed concern that these stated declines “may well be a result of the ‘mining’ of our nation’s soil fertility by intensive chemically based agriculture”.
“Soil structure is the arrangement of solid parts and pore parts within the soil. Soil structure has a major influence on water and air movement, biological activity, and seedling emergence. Soil is a complex system that is affected by several environmental factors, like erosion, deforestation, and urbanization. Without interference, the total loss of soil structure leads to nutrient depletion.”