The article by Dov Pasternak about lablab (in this issue) reminded me of material in ECHO’s files from many years ago. Reimar von Schaaffhausen, working in São Paulo, Brazil, sent articles and letters over the years about the valuable role that lablab (and pigeon pea [Cajanus cajan]) have played in providing feed for livestock during the dry season. The information is summarized in the next several paragraphs.
Sometimes the smallest of things can impact human health beyond all proportion to their size. Trace elements are an example of this. Trace elements in an amount that is either above or below certain thresholds in soil, animal feed, or the human diet can have important impacts on the health of both livestock and people.
Everything around us—solid, liquid and gas—is made up of some combination of the one hundred or so elements that are part of creation. Some elements, like carbon, oxygen, and hydrogen, are rather abundant. Others, such as zinc, copper, or mercury, are much less abundant and are called trace elements, because they are found in trace amounts. We are all exposed to trace elements through our food, water and air, and they can significantly impact our health if exposure levels are too low or too high.
An important principle of conservation agriculture is that of targeted, precision applications of organic or inorganic fertilizer near crop plants, as opposed to evenly dispersing inputs over an entire field. In a row-crop setting, this can be done by banding fertilizer next to the crop plants. In systems such as zai or Foundations for Farming, fertility inputs can be placed within small planting basins in which the crop seeds are sown.
During the first growing season of a zai study that ECHO is conducting in South Africa, soil nutrients were higher in manured than in non-treated zai pits. In season two, we wanted to further document the effect of targeted (near sorghum seedlings) versus dispersed cow manure. To do this, we added flat-ground treatments including 1) flat ground with broadcast manure and 2) flat ground with the manure concentrated near the sorghum plants. Each treatment was replicated four times in a randomized complete block design.