ESTABLISHMENT OF ORCHARDS
Orchard establishment is a highly specialized activity, which requires proper planning, selection of site, land preparation, layout, planting of saplings, as well as orchard protection and management.
Selection of site and soil
Lychee can be cultivated in a wide range of soils, starting from sandy to clay loam with good drainage and rich in organic matter. However, well-drained deep sandy loam soils having good moisture holding capacity, rich in organic matter and calcium content have been found ideal for lychee cultivation. The well-drained soils rich in calcium content have been observed to be most suitable for better growth and quality fruits. Soils with poor physical conditions, lacking in available nutrients can be improved for lychee cultivation by adding sufficient quantities of decomposed farmyard manure (FYM), compost and green manure. Lychee growth is restricted in clay soil, thus the site selected should have the above characteristics. When selecting the site, climate also given due consideration. Lychee should not been grown in excessively humid regions when winter temperature is not below 12°C. Also when selecting a site the source of water and transport facilities should be given due consideration.
Before layout the land is cleared of bushes and other weedy vegetation and is leveled with a mild slope in the opposite direction of the water source. To improve the fertility of the soil organic matter is added. A green manure crop is grown and incorporated into the soil, which improves its fertility, moisture holding capacity and physical condition.
Pits 90 x 90 x 90 cm in dimension are dug at the spacing decided for the orchard. Pit opening is normally recommended in April-May to have a sterilization effect for about 3 days. Before the onset of monsoon pits are filled with topsoil mixed with about 40 kg decomposed compost, 2 kg neem/karanj cake, 1 kg bone meal/single super phosphate and 200-300 g muriate of potash. Incorporation of about 2 baskets of soil from the root zone of old lychee trees encourages the mycorrhiza growth. Then the soil is allowed to settle with the first few rains and leveled properly. Planting is done during June to July. At the time of planting a hole the size of ball of earth is made in the centre of the pit at the marked point where the plant is fixed and the soil is pressed to remove air. Watering is done immediately after planting for proper establishment. Subsequently the plant is regularly irrigated till it is properly established.
Spacing and planting system
Lychee is an evergreen spreading tree, which attains the height of about 10-12 m at its full growth and development. Light penetration of its canopy is also desirable for proper fruiting, hence planting in square system at a distance of 9-10 m within and between the rows has been practiced. Planting of lychee in a double hedgerow system at a distance of 4.5 x 4.5 x 9 m accommodating 329 plants/ha has been found to be the best and gave higher yield of equally good quality fruits up to 16 years of plantation. High density planting adopting a double row system has also been found to be superior at other locations in terms of yield and quantity of fruits. Through appropriate canopy management high density planting accommodating about 1,200 plants per hectare could also be done as has been found successful in mango. However, this would need further investigation.
Training and pruning
Training of the plant in the initial stage is essential to provide the required framework. Unwanted branches should be pruned to provide definite shape and to promote growth of the trunk and crown of the tree. Three to four branches 60-75 cm from ground opposite to each other are allowed to form the proper frame of the tree. Further, crowded and crisscross branches are removed to facilitate better growth. The branches with narrow angles are also avoided as they are prone to breakage. Non-fruiting unproductive branches inside the canopy in growing and mature trees should also be pruned. Dried, diseased and scissors-shaped branches should also be periodically removed. Light pruning after harvest has been found congenial for better growth, fruiting and yield. While harvesting the fruit the panicle is plucked along with 8-10 cm of twig to promote new flush and better bearing for the succeeding year.
Manure and fertilizer
Among the several factors associated with production of lychee, balanced nutrition is considered to be the most important which determines productivity and quality. Lychee responds to exogenously applied manure and fertilizers and response varies depending upon cultivar (Kotur and Singh, 1993), climatic conditions and soil types. A survey conducted in the Doon valley indicated that 80 percent of orchards are low in N and P and need N and P application (Kunwar and Singh, 1993). In West Bengal, NPK was reported to be below the optimum level (Rao et al, 1985). However in Punjab N, K, Mg, Zn and Mn are reported to be in deficit range. Recently, a survey conducted by Babita (Personal Communication) has clearly shown that low yield and poor quality fruits in lychee are associated with a sub-optimal range of nutrients. Variation in nutrient content was also observed among varieties.
Field experiments conducted on different cultivars at different locations have clearly demonstrated the effect of a graded dose of NPK on growth, yield and quantity of fruits. Application of 600-800 g N, 200-300 g P2O5 and 400-600 g K2O per plant is recommended for 12-15 year old trees. Nitrogen and Potassium should be applied in 2-3 splits and P2O5 in two splits. Excessive application of nitrogenous fertilizer before flowering should be avoided. Phosphorus application at the time of flower bud differentiation improves flowering and fruiting. Application of cakes and manure is generally practiced to get better quality fruits. In general, lychee orchards maintained with higher doses of organic manure have better yield and quality as compared to orchards maintained with chemical fertilizers.
Additional application of Ca, Zn, B, Cu and Mn is recommended. Application of 0.6 percent Ca as calcium chloride improves fruit weight and quality. Zn is applied in the form of 0.5 percent zinc sulphate hydrated with lime, which helps in reducing fruit drop and enhancing fruit yield and quality. Boron in the form of borax (600 ppm) enhances fruit setting and reduces fruit cracking.
In acidic soil application of 10-15 kg lime/tree once in 3 years has been found to increase the yield. In general, application of FYM, potassic and phosphoric fertilizers in major lychee growing areas of the country is done during June-July, just after harvesting of the crop.
However, in heavy rainfall areas like West Bengal, Uttaranchal, and Uttar Pradesh, manure and fertilizers are applied in the month of September-October just before the end of monsoon. The nitrogen is applied in two equal spilt doses. The first dose is applied after fruit set, in the month of March-April while the remaining half dose is applied immediately after harvesting of the crop. After application of fertilizer, irrigation of the tree is essential to maintain proper soil moisture. The total requirement of nitrogen, phosphorus and potash is applied through basal application. However 2 percent urea spray is practiced once or twice during the period of fruit growth as needed.
Foliar application of zinc sulphate (0.1 percent) is done twice, 10-15 days before flowering for improving sex ratio and to reduce fruit drop. If a deficiency of zinc and magnesium is observed, application of 150-200 g ZnSO4 and 150-200 g MgSO4, respectively per plant during September has been found to be beneficial. Foliar application of 0.1 percent borax, 2-3 times during the period of fruit growth and development of the trees enhances fruit retention, minimizes cracking, improves fruit colour and sweetness, and advances maturity. Other micronutrients like Fe (Ferrous sulphate), Cu (Copper sulphate), Mg (Magnesium sulphate) are applied if deficiency symptoms are observed. Two to three spray in a year is sufficient to maintain the trees in good health.
Foliar application of the plant bio-regulator, NAA (20 ppm) at an interval of 10-15 days during the period of fruit growth and development, twice or thrice, has been found to be useful for minimizing the fruit drop. IAA may be substituted for NAA if the latter is not available. Spraying plain water four to six times in the early morning hours of the day during the advanced stage of fruit growth and development have been found to be highly effective for achieving better growth with minimized fruit cracking.
Monitoring of plant nutrients is done arbitrarily although some farmers get their soil analyzed for pH and nutrients content once in a while. However, it is advocated to use leaf nutrients as diagnostics for monitoring nutrient needs (Kotur and Singh, 1993). Application of fertilizer based on leaf analysis values, though holding promise, is not yet a reality. Babita (Personal Communication) observed that the critical value of nutrients could be used as a guide to determine the nutritional needs, and could economize on fertilizer and provide higher yields of quality fruits.
Irrigation, mulching and water conservation
Lychee being an evergreen plant, the maintenance of optimum soil moisture is critical for growth, development and fruit production. If the rainfall is evenly distributed lychee is grown successfully and supplementary water requirement depends upon cultivar and evaporation demand. Water requirement ranges from 600-800 mm. Investigations carried out to determine the irrigation needs have clearly indicated that irrigation is critical at the fruit development stage to get better yield and quality of fruits. Interestingly, differential management of water in the vegetative phase and reproductive phase is also suggested. To achieve faster growth of the plant no water stress should be permitted, while in the reproductive phase water stress is beneficial at the time of fruit bud differentiation. Light irrigation during summer and winter months and cleaning of the basin is advocated. Irrigation at the intervals of 2-3 days during the initial stage of plant establishment is considered essential. Further, the young plants should be irrigated during dry periods and winter months at intervals of 3-5 days. For young plants mulching with dry leaves or residues in the basin help in better moisture conservation. Experiments conducted at Ranchi indicated that irrigation of plants at alternate day intervals, 6 weeks before harvesting improves fruit retention, encourages better fruit development, and minimizes the cracking, apart from the quality of fruits. Certain physiological disorders like poor sex ratio, poor fruit set, heavy fruit drop and high fruit cracking, besides sunburn of the fruits can be minimized with proper water management. The basin or flood method of irrigation is normally practiced. However, adoption of drip irrigation has been found to be effective in the economic use of water and enhanced growth, especially in an area where water availability is not satisfactory.
Moisture conservation through mulching using dried weeds or black polythene sheet has been found useful. Trials have also been conducted to conserve moisture using farm residues and polythene sheets. Through adoption of mulching, frequency of irrigation is reduced. In a trial conducted at Ranchi mulching with 3 irrigations was effective in reducing cracking and enhancing yield and quality of fruits (Singh, 1986). To check fruit cracking mulching with 3-4 irrigations during fruit growth has been found to be satisfactory.
Filler plant and intercropping
Lychee is a slow growing plant and takes about 15-16 years to develop canopy and cover the area. During the initial period of establishment, the space between the plants can be utilized for planting of filler plants/intercrops. The planting of guava, custard apple, lime/lemon in the centre, between and within the rows of lychee have been found to give additional income in the initial stage of planting without competing with the main crop. Papaya is also planted as filler plant at the spacing of 2.5 x 2.5 m. In between the plants in the initial stage, cowpea, french bean, okra, brinjal or other suitable crops of the regions are grown as intercrops. In the mature lychee orchards, cultivation of partial shade loving plants (ginger, turmeric, elephant foot yam) is practiced successfully, which provides additional income.