Conclusions

Use of polymers to increase survival rates

Trees are at their most vulnerable just after transplanting. a prolonged drought can cause saplings to die or to become stunted and twisted. Polymers placed in the root zone of the saplings will ensure they have more secure access to moisture. one effective method is the use of water pads; in this application, the polymer water pads are held in place by wedging them between jute and brown paper.

CONCLUSIONS

Safety considerations and maintenance of the trees are the most important considerations for the establishment of roadside plantings, which require careful planning and preparation. To ensure the effort and expense of planting is not wasted, the resources and arrangements necessary to maintain the trees and keep them alive should be confirmed in advance. nursery seedlings often die because of animal damage, high surface temperatures, high evapotranspiration rates, lack of soil moisture, and competition with other vegetation. In general, only the number of trees that can be ensured to survive and thrive should be planted.

Water is the main constraint when establishing new plantings. Trees and shrubs should be watered systematically at the time of planting and several times during the first two years. Irrigation bags or large containers that will trickle water into the soil are convenient for irrigating large plants. Sandy or rocky soils have low water-holding capacity, causing wetting fronts to travel deeper and in a narrower band. Less water but more frequent irrigation is recommended for these soils. on the other hand, finer textured soils, such as loams and clays, have a higher water-holding capacity and wider wetting fronts. More water can be applied in these soil types and at less frequent intervals than in sandy soils. To help prevent disease, it is important not to wet the leaves or needles of trees.

Seedling quality will influence the amount of water needed. Healthy seedlings grow new roots faster and can access deeper soil moisture. Poor-quality seedlings develop roots slowly and must be irrigated more frequently. Seedlings must adapt to the new location, as well—in the nursery they were watered daily, but now they must be hardened to sustain their new environment. To help them adapt and survive over time under harsh conditions, the amount and frequency of watering should be reduced until the tree has fully adapted and can survive on its own.

Moreover, when weeds and other undesirable vegetation are growing near planted seedlings, soil moisture is depleted sooner, requiring more frequent irrigation than if seedlings were free from competing vegetation.

Because roadside plantings require care, plans for their maintenance and management must be identified (box 12.2). numerous methods can work. The question is not so much which method is best, but whether there is a clear arrangement in place. Given that roadside tree plantings are often dispersed across a large area, arrangements for local management are generally most successful. Three additional factors that contribute to effective management are (a) restrictions to the free movement of cattle and ruminants, (b) clearly assigned ownership and usufruct rights to the roadside planting, and (c) the ability to economically use the plantings, even if it means harvesting and replanting.

BOX 12.2

Roadside vegetation maintenance practices

The following techniques are applied to protect roadside vegetation.

Mulch. Mulch is a protective material placed on the soil surface to prevent evaporation, decrease surface temperatures, avoid weed establishment, enrich the soil, and reduce erosion. applying mulch immediately after planting and maintaining it for several years helps hold moisture in the soil and suppresses weed germination. Several materials can be used as mulch, such as wood fiber, erosion mats, hay, straw, and compost. on sites where vegetation is expected to take several years to establish, such as arid or high-elevation sites, mulch that will last more than one year should be applied. Materials with the highest durability include most long-fibered wood mulches, as well as erosion mats made from polypropylene. Straw, hay, and short-fibered wood products are less likely to be present after the first year. Mulching around seedlings is especially recommended for hot and dry sites and those with competing vegetation but is less important on sites with less potential for competing vegetation to become established during the first several years after planting. Mulching is also less critical on sites with low evapotranspiration rates or high rainfall.

Pruning. Well-spaced structural branches should be developed early in the life of a tree. Branches that grow close together when trees are young will grow into each other with age and will be unable to develop their full structural strength. once the structural branches have been established, little pruning should be needed. It is advisable to examine the trees yearly and prune or cut branches for reshaping, if necessary. Uncontrolled growth of trees and shrubs could cause problems for vehicles, such as reduced sight distance and vehicle damage or personal injury. Trees also need to be pruned to remove dangerous hanging branches or to prevent lower branches from blocking a path or obstructing visibility.

Protecting the seedlings. fencing will be necessary in free-grazing areas and other circumstances where plantings are subject to damage. Social fencing is sometimes considered an alternative to a physical fence. If all the residents of the area agree to keep their cattle off the planting, and if there is no risk of cattle from other villages encroaching upon it, establishing the planting without a physical fence may be possible. However, social fencing is particularly challenging in roadside plantings that often cross several districts. a range of methods can be used to protect seedlings, including rigid and nonrigid netting, fencing, and animal repellents. fencing materials that allow enough sunlight for photosynthesis are preferred. Stone or brick fences are not advisable because they block sunlight and impede plant growth. Individual trees can be fenced by surrounding them with sticks made from small branches from nearby trees.

Plastic netting can be installed to protect seedlings from animals browsing. The netting acts as a barrier to foraging for foliage, stems, and even root systems without impeding plant growth. There are two general types of netting: rigid and nonrigid. nonrigid netting is a soft, fine-mesh plastic material. When installed on a seedling, it fits perfectly around the seedling. Rigid netting has larger mesh openings and keeps its shape when installed. Rigid netting, although typically more expensive, is usually preferred over nonrigid netting because it is easier to install and seedling growth inside the netting is less restricted. netting must be installed as soon as possible after planting to ensure immediate protection.

Tree shelters are translucent plastic tubes placed around seedlings after planting. They create a favorable growing environment while protecting the seedling from animal damage. Tree shelters enhance plant growth by creating a microclimate with lower light intensities, higher temperatures, and higher humidity. Tree shelters should be considered for sites where the potential for animal damage is very high. Tree shelters are not suitable for all species or site conditions. Tree shelters must not be removed until a portion of the seedling crown has grown out of the shelter. If the tree shelter is removed while the seedling is still growing inside the shelter, it will not be capable of supporting itself. Tree shelters are more effective than other protective methods, but are also costlier.