The Soil factors that include soil moisture, texture, chemical composition and temperatures govern features such as the lifetime of the orchard, fruit quality and productivity.
A suitable soil is a basic requirement for a particular crop. Before deciding a particular production system, one should thoroughly check soil conditions of the available land.
Therefore, an analysis of soil type, its fertility and land degradation etc. is needed for each alternative under consideration. Knowledge of the effects of various soil and climatic conditions on fruit growing is essential for every successful fruit grower, as different fruits differ widely in their soil and climatic requirements.
A fruit crop has particular soil requirement to grow well. Among the main criteria, the 'physical environment' and 'sanitary environment' aspects of the site are essential.
Fruit trees will do well only if the soils are deep, well drained and without hard pan underneath. Soil requirements and management of soil constraints for different fruit crops based systems are as hereunder.
Citrus:
Citrus is endangered more by the consequences of too much water than by temporary rationing.
Poorly drained low-lying zones and very heavy soils with a hydromorphic tendency should be ruled out.
Ideal sites for laying out orchards have light and above all well filtering soil, a neutral to slightly acid pH (6 to 7.5), no excess limestone and sufficient organic matter.
The management of minor defects such as alkalinity, slight salinity, etc., can be handled partly by the choice of suitable stock and possibly appropriate orchard management techniques such as the application of organic-mineral amendments before planting.
As grapefruit varieties are extremely susceptible to Phytophthora and other diseases affecting the trees, high quality planting material must be used and planted with the graft 30 cm above the soil.
Planting distances vary according to the climatic zone and rootstock vigour. Density is about 6 x 4 m or 6x 6 m in Mediterranean countries and the trees are spaced more widely in the humid tropics (8 x 8 m or more) where growth is continuous and the trees developed more rapidly. Wind-breaks must be planted around the orchards in exposed locations.
Orchard soil maintenance:
Trees do not cover the entire space available in an orchard. With a few rare exceptions, the land must be protected during the rainy season.
Permanent or temporary grassing depending on the availability of water is the most common management technique.
The grass strip is generally limited to the central part of the inter-row.
Weed growth below the tree foliage is controlled by one or two applications of herbicides each year. In zones with a long dry season, it is preferable to choose a cover crop that withers and does not compete with the trees for water.
Apple:
Although apple trees will grow well in a wide range of soil types, a deep soil ranging in texture from a sandy loam to a sandy clay loam is preferred. A minimum soil depth of 4 feet is desirable.
Very heavy soils are not desirable for apple growing. Apple trees will not thrive in a soil that is poorly drained or subject to water seepage.
If free water is allowed to persist in the soil, the trees will suffer. Roots of affected trees will die and this will eventually result in die back of the aerial parts.
Installation of drains in areas subjected to seepage water or where water table comes within 4 feet of soil surface at any time of the year are advisable.
Since availability of nutrients is adversely affected by an excessively high or excessively low pH, a pH of 6.5-7.0 is most suitable for apple trees.
For soils with low pH and in orchards where through years of irrigation and fertilizer use, soil pH has dropped to an extremely acidic state, use lime to correct the pH.
On the other hand high pH tends to cause most trace elements and some major elements to be less available to the trees.
Application of calcium sulfate or use of ammonium sulfate may improve availability of a nutrient such as iron.
Grapes:
Soil structure is more important for grapes than fertility status. Grapes require a well drained soil, especially in tropical south India, where the development of roots coincides with stagnation of water continuously for several days during rainy season, damaging the roots. Also desiccation of soils reduces root growth, resulting in cessation of new growth in V. vinifera in the tropical areas.
The brown and gray soil series and the heavy black soils of Maharashtra are not suitable.
The later soil has 1% or more salt concentration but the chloride injury should be avoided. However, damage to grape vine by salt stress may be minimized by exogenous application of proline or cytokinins in the initial stages, and gibberellins at the later stages of the planting.
Though, the cultivars differ markedly in tolerance to salt, grapes can be grown on soil with higher salt concentration by using resistant rootstocks like ‘Salt Creek’, V. riparia, V. rupestris 3309, ‘ARG No. 1’, and ‘ARG No. 9’.
Most of the micro-nutrients become unavailable under high soil pH conditions, which can be supplied through foliar sprays.
Important micro-nutrients generally applied through spray include zinc, iron, boron and manganese. Foliar application of 0.2% boric acid applied at pre-bloom and bloom stages for the improvement of fruit quality and yield in Thompson Seedless grapes.
Micro-nutrient sprays apart from improving fruit quality and growth of vines also improve berry set, berry retention and yield. For concentration and timing of application, it is advisable to adhere to location specific recommendations.
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