Agro-forestry and Alley Cropping In Sustainable Agriculture. "TinasheSpeaks..."

Introduction

Agro-forestry systems and alley cropping systems are intertwined as both systems involve the amalgamation of either leguminous or non-leguminous trees and crops on the same piece of land. Trees will will come in as wind breaks to do away with pests, diseases and weeds that are dispersed through anemochory (wind). In addition, trees will allow crop production on steep slopes which are prone to massive soil erosion and they will also aid in nitrogen fixation. Moreover, trees will therefore be of a longrun investment whereas the crops will allow cash flow within the shortrun. However, the choice of the trees has to consider those trees that do not have allelopathic (poisonous) effects on the crops.

Alley cropping on the other hand, it falls under the umbrella term "agro-forestry" but the trees have to be leguminous and fodder trees that create a symbiotic relationship with the crop and at the same time add value to the soil through green manuring which is done sequentially. The trees in alley cropping can be fed to animals as protein supplements.

Discussion

Fodder trees are one of the major components for alley cropping systems, agro-forestry systems and even as livestock feed. The herbage is pruned three to four times for green manuring and or feeding livestock.

There are abundant local legume trees and shrubs potentially suitable for alley cropping systems in the sub-Saharan Africa, which are yet to be studied. The nitrogen contribution of two years old Albizia lebbeck and Senna corymbosato to the yield of maize grown in alley cropping was compared to that of Senna siamea, Gliricidia sepium and Leucaena leucocephala in four seasons at Ibadan.

Albizia lebbeck 

Common names of Albizia lebbeck include lebbeck, lebbek tree, flea tree, frywood, koko and woman's tongue tree.

Senna corymbosato

Common names of Senna corymbosato are Argentine senna, Argentina senna, buttercup bush, flowering senna, Texas flowery senna or tree senna.

Senna Siamea

Common names of Senna Siamea are Siamese cassia, kassod tree, cassod tree and cassia tree.

Gliricidia sepium

Common names of Gliricidia sepium  include Gliricidia, quickstick, mata ratón; cacao de nance, cachanance; balo in Panama; pi?on Cubano in the Dominican Republic; madreado in Honduras; kakawate in the Philippines; madre xacao or madre de cacao in the Philippines and Guatemala; madero negro in Nicaragua); and wetahiriya in Sinhala. Gliricidia is a medium size leguminous tree belonging to the family Fabaceae. It is an important multi-purpose legume tree.

Leucaena leucocephala

Common names of Leucaena leucocephala include white leadtree, jumbay, river tamarind, subabul and white popinac. Leucaena leucocephala is a small fast-growing mimosoid tree native to southern Mexico and northern Central America (Belize and Guatemala)and is now naturalized throughout the tropics. L. leucocephala is used for a variety of purposes, such as firewood, fiber and livestock fodder.

Calliandra haematocephala

Common names of Calliandra haematocephala are powder-puff, powder puff plant, and fairy duster. The genus comprises herbaceous perennial plants, shrubs and rarely small trees, growing 0.5–6 m tall, with bipinnate leaves. The flowers are produced in cylindrical or globose inflorescence and have numerous long slender stamens. These plants flower all year round, but the best blooming is in spring and summer. They can be easily pruned.

Okogun et al (2000) concluded that maize shoot biomass and maize grain yield in A. lebbeck alley compared favourably with that in G. sepium and L. leucocephala. Maize biomass and grain yield in S. corymbosa alleys were the lowest. Within A. lebbeck, L. leucocpehala, and G. sepium alleys there were no significant differences in the maize yield in the alleys that received 0, 40 or 80 kg N/ha. Application of more than 40 kg N/ha in S. corymbosa alleys was not necessary as there was no significant increase in maize yield at the higher level of nitrogen. Maize yield and N uptake in A. lebbeck alleys were not significantly different from yield and N uptake in G. sepium, and L. leucocephala at the same fertilizer level. There was a significant correlation between hedgerow tree biomass and maize grain yield. At the end of twelve weeks after pruning application, the organic residues of the pruning applied in the alleys ranged from 5% in G. sepium and 44% in A. lebbeck in the first year compared with the original pruning applied which showed that the slow rate of A. lebbeck decomposition could have a beneficial effect on the soil. The maize N recovery from applied N fertilizer was low (10–22%). Percentage N recovery from the prunings was low in the non-N fixing trees (12–22%), while the recovery was high (49–59%) in A. lebbeck as well as in the other nitrogen fixing tree prunings. Thus A. lebbeck, apart from enhancing maize growth and grain yield like in L. leucocephala and G. sepium, had an added advantage because it remained longer as mulching material on the soil because of its slow rate of decomposition. It was able to survive pruning frequencies with no die-back. This indicates that A. lebbeck is a good potential candidate for alley cropping system in West Africa. S. corymbosa performed poorly compared with the other legume trees. Though it responded to N fertilizer showing a positive interaction between the hedgerow and fertilizer application, it had a high die back rate following pruning periods and termite attack.

Conclusions and Recommendations

The adoption and implementation of agro-forestry and alley cropping systems is strongly recommended as it helps in crop protection from weeds, pests, diseases and soil loss through erosion. On the other hand, it aids in the provision of nutrients as they are leguminous trees that naturally fix atmospheric nitrogen. In livestock feed supplementation, Calliandra haematocephala is not supposed to be fed too much for it builds up infertility in animals.

Reference

Okogun, J.A., Sanginga, N. and Mulongoy, K., 2000. Nitrogen contribution of five leguminous trees and shrubs to alley cropped maize in Ibadan, Nigeria. Agroforestry Systems, 50(2), pp.123-136.