Sri Lanka Dry Zone

Traditional settlements in the dry zone have undergone several changes. An important one of them is the shift of location or the expansion of the hamlet towards the upper portion of the land catena. This has led to reduce the dissimilarities between home gardens in traditional villages and that in major irrigation schemes. Soil moisture deficiency and infertility make this environment somewhat precarious for rapid development into a matured home garden. Observations indicate that these home gardens are slowly progressing towards an ecologically sound vegetation which consists of a mixture of endemic and introduced plant species. Hence, the anatomy of matured home gardens in the dry zone can be used in planning new settlement areas as it has been time-tested to become sustainable. Results of a home garden survey carried out in the central dry zone showed that the presence of a water source makes a significant impact on the floristic composition of the homestead. There is a distinct ratio between the large tree density of endemic and introduced plant species, but the ratio is different depending upon the availability of water. Although the total plant density of introduced species is higher than that of endemic species, a higher density of natural large trees is found in the dry zone home gardens. This attributes to the fact that endemic species are grown better under the harsh soil and moisture conditions creating a favourable microclimate for the introduced species. Adoption of such a strategy learnt from nature could definitely result in a successful home garden model for the dry zone conditions. The paper introduces the relevant guidelines for planning home garden vegetation on the basis of data gathered in the study.

A case study was carried out in the Maha Kanumulla village tank cascade (Anuradhapura) to understand the present status of land and water resource utilization in the dry zone of Sri Lanka. The study consists of tank water balance study, ground water survey and socio economics survey in order to determine the potentiality and present level of resource use. Results show tbat the existing village tank hydrology does not encouragre efficient use of water under the present system of land, water and structural management.

The irrigable lowland under village tank has been seriously fragmented with respect to the ownership, so that any introduction of better water management method would be challenging. The traditional shifting cultivation has exploited almost all catchment areas of village tanks and been waiting for strategic action towards a gradual recovery while using the land for agriculture as the demand for Iand cannot be overwhelmed. Investigation on the potentiality of groundwater for small scale irrigated farming would be useful. The paper makes some suggestions to improve the system hydrology and optimum use of land for farming.

KEY WORDS: Land and Water Resources, Village Tanks

Declining soil fertility and moisture stress have been identified as the main physical constraints in the dry zone rain-fed agriculture. Both these constraints are surfaced with accelerated soil erosion taking place in rain-fed upland farming areas. The erosion becomes hazardous in these lands due to reasons such as high soil erodibility, shallow soil depth, occurrence of erosive rains when the land is bare and vulnerability of already degraded lands to further erosion. A study carried out at Mahailluppallama with the objective of finding the effectiveness of various soil conservation practices has led to developing a Soil Conservation Impact Assessment (SCIA) Model for use in soil conservation planning. The SCIA model provides opportunities to compare effects of different mulch types, rates and land management practices on soil erosion, which will lead to select an effective soil conservation package for a farmer on the basis of his resource availability and preference. The model suggests that the conventional type of bunding is not adequate to reduce the soil loss to a permissible limit. Use of a mulch without any other land management method also does not protect the soil adequately. Mulching if combined with conventional bunding is an effective measure to control soil erosion. Alley cropping with gliricidia planted on small graded ridges and mulch strips with live leguminous creepers (Mucuna utilis, Centrosema pubescen) perform well in controlling soil erosion in the dry zone rain-fed upland farming.