Mixed Systems based on Crop Residues

Mixed farming crop residues systems are defined as systems where crop residues are collected and conserved to feed livestock on the farm.

Most time of the year animals are still grazed on communal areas where they compete for feed with livestock from other systems. Common reasons to collect and store crop residues are:

- prevent other livestock to consume farm crop residues strait after harvest;
- reserve feed for periods of feed scarcity (dry season, winter time);
- use residues from own fields that can not be reached by own livestock;
- have more feed for selected animals (i.e. draught animals, fattening sheep).

The role of livestock at the farms concerned is still similar as for the mixed crop farmer described in the communal grazing sub system. However, the composition of herds by species and animal type may have changed:

- cattle in productive stage at farm, others if any sent to herds in grazing systems
- relatively more goats and / or sheep, grazing fallow and communal areas
- relatively more draught animals

The system is mainly found in semi arid sub humid and hilly areas where there is an increasing competition for feed resources from communal grazing areas and for crop land. As such the presence of this system can be an indicator for such pressures.

The quantity of crop residues that can be collected depends mainly on the area cultivated, crop type and cropping density. Legumes provide residues with a high protein content. Available quantities are often small (low production per ha, small areas cultivated) while transport and storage losses can be high (loss of dry leaves). In general cereals are cultivated at a larger scale and provide more residues per ha but quality is poor (low protein content, poor digestibility). At best it is just good enough the prevent animals loosing weight. As long as better quality feed is available crop residues may not be used while being available.

The major effect of crop residue harvesting is internal transfer of organic matter and plant nutrients on the farm.
With the crop residues all the above ground organic matter and with it as much plant nutrients as with the crop (or even more) are removed from the field. The major share of plant nutrients and about half the organic matter ends up in manure on the farmyard. During decomposition of crop residues by animals in manure and during storage of manure major losses occur. The remain manure still has to be transported to fields. In general, this is to fields nearby the home stead because of transport constraints and / or as part of the farmers strategy. As a result of crop residue harvesting the soil fertility of further away fields may decline at an accelerated rate, while soil fertility of nearby fields may be maintained.

The decline in soil fertility may even be further accelerated through the use of animal traction.
With animal traction the marginal level of production per ha is in general 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.

The potential of this subsystem to produce more livestock products is limited and may even be declining as a result of decreasing communal resources and limited feed value of crop residues

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