1. trees grown in managed hedgerows still perform the same functions as in the traditional bush fallow system for nutrient recycling and soil fertility regeneration;
2. hedgerow pruning supply in-situ mulch and green manure;
3. partial shading by the hedgerows during off-sea son helps in weed suppression;
4. inclusion of N-fixing legumes add N to the system;
5. presence of woody species aids in soil and water conservation;
6.hedgerows also serve as a source of browse and other auxiliary products, such as staking material and firewood.
Biologically, the success of the alley cropping system depends on; (1) correct choice of woody species; (2) successful hedgerow establishment; (3) efficient hedgerow and crop management.
Although a large number of MPTS are potentially suitable for use in alley cropping, only a smallNumber of species has been thoroughly tested the following n-fixing leguminous species have been shown to be suitable for use in tropical cropping
1 gliricidia sepium and leucaena leucocephala for use on high base status soils in the lowland humid zone.
2.cajanus cajan calliandra calothyrsus erythrina poeppigiana and fleminggia for use at higher altitudes.
3.flemingia macrophylla and dactyladenia barteri for use on acid soils in the humid zone.
Further research to identify other n-fixing mpts for use on acid soils.
Traditional alley cropping systems have been praised for some time in the Ethiopian highlands on acid soil in southeastern Nigeria and on degraded and sloping lands in southern Philippines and eastern Indonesia these system were used by traditional farmers to sustain low yield coop production with no external chemical input or source of brose and other auxiliary products.
The alley cropping technique has been tested and used for the production of various food and forage crops. In the past two decades a large number of alley cropping trials have been carried out in various coziness of the humid and sub humid tropics although most of these trials dealt with the adaptability of the system they have also yielded information on the potential and limitations of this technique the technique has given good results on high base status soils with moderate fertility However on acid and low fertility soils where both hedgerow species and associated crops tend to have shallow and retired root growth below ground nutrient competition between woody and crop species can become a major problem results of trials in the semi-arid zone have not been encouraging as moisture competition between hedgerows and crops is a major problem