Risk Overview:
ixed Crop Residues

Below are presented the principal positive LxE (+) and negative LxE (-) impacts of livestock on the environment. An overview of Risks and Opportunities by problem area is presented in the Risk Matrix Mixed Crop Residues

LxE (+)

The principal positive impact is the potential contribution of livestock to sustainable crop cultivation on fields nearby the farm.
NB The number of Tropical Livestock Units per ha cropland and the amounts of crop residues are usyally not sufficient to produce enough manure for all the land under cultivation.

LxE (-)

The principal negative impact is the internal transfer of plant nutrients on the farm, resulting in an acceleration of soil mining and land degradation of fields further away from the farm.

Where the crop residues are used as feed all the above ground organic matter is removed from the field. They contain as much or even more plant nutrients than the crop harvested. The export of plant nutrients from the field is about twice as high as if the crop residues were grazed in the field (see livestock / cropland ratio). During digestion of the feed and during decomposition of manure in the kraal losses occur. The remaining manure (about ¼ or less of the crop residues harvested) has to be transported to fields. Because of transport constraints and because of the limited amount this is often to fields nearby the homestead.

The decline in soil fertility may be even further accelerated through the use of animal traction.
With animal traction more land can be cultivated while the marginal level of production per ha in general is at a lower level than without. This often results in prolonged cultivation and shortened fallow periods, both resulting in an accelerated decline of soil fertility and soil structure.

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