Restoring the Soil - Canadian Foodgrains Bank

Existing Green Manure/Cover Cropping Systems Around The World132. The slow results. Soil improvement is a long-term process that may not be immediatelynoticeable to the farmer. Usually, significant improvement in productivity doesnot occur until after the first crop of gm/cc has been applied to the soil, which meansthat concrete, visible results are not apparent until well into the second cropping cycle.This slow appearance of results—improved soils—that are often difficult for people tobelieve, further complicates the adoption of gm/ccs. Once again, it is often preferableto promote gm/ccs for some reason other than soil fertility. If farmers are not awareof the value of organic matter in their soils, a heavy application of animal manureon a small plot of land the first year will help make farmers aware of the value of theorganic matter the gm/ccs are producing in their fields (Photo 7). Simple demonstrations,such as showing how organic matter increases the water-holding capacity of soil,can also be used.3. Dry season problems. Often gm/ccs must produce their organic matter at the endof the wet season, or must continue to grow during the dry season. Grazing animals,wild animals, termites, agricultural burning, bush fires or several other problems maydestroy organic matter or growing plants before the farmer can use them the followingrainy season. In very hot climates and on soils with no shade, the nitrogen and muchof the organic matter will be burned off by the tropical sun. Thus, almost no benefitfrom the gm/cc will be available for the next crop.4. Difficult growing conditions. Smallholder farmers in the tropics commonly copewith many challenging conditions, including extremely low or irregular rainfall,extremes in soil pH, severe drainage problems, or a combination of these. Such conditionswill reduce the growth of gm/ccs, thereby reducing or destroying their impact.Through the years, we have learned how to overcome an increasing number of suchproblems. The solution is often to use gm/cc species that are particularly resistant tocertain problems. For example, jackbean can withstand very poor soils and is oftenused for recuperating wastelands. However, these solutions are often achieved by usinggm/cc species that produce less organic matter, don’t fix as much nitrogen, don’t haveadditional benefits, or don’t fit as well into the local farming system.5. Timing (also called “synchronization”). The nutrients provided by the gm/ccs,especially nitrogen, must be available to crops when they need them in order to raiseproductivity. Gm/ccs will boost farmers’ productivity only if the gm/ccs’ nutrients areavailable to the crops at the right time. In many gm/cc systems, the correct timing iseither impossible or very difficult to achieve. Therefore, the efficiency of the systems isreduced.Very often, this problem can be solved using natural foliar nutrient sprays at theappropriate time of year to supplement soil nutrients. Solutions of cattle urine orcrushed mother of cacao (Gliricidia sepium) leaves are often used. Very small amountsof chemical fertilizer can have the same effect. These remedies can be very useful insupplying nutrients at exactly the time the crops are likely to run out of the nutrientssupplied by gm/ccs.