Cultivation practices of Avacado

Cultivation

Planting

          Before establishing a plantation, the field should be well ploughed, harrowed and leveled, keeping in mind the possible intercropping, often with vegetables. The commonly recommended spacing is 7m × 7m, but it may vary from 6–12m on the square. The spacing is determined by the crown size of the variety and soil type. Trees in deep soils with a high percentage of organic matter need more space, because they grow taller and larger under these conditions.

  

           Pits of 60cm × 60cm × 60cm are dug and left open to sun for about 10 days. These are then filled with top soil mixed with approximately 30kg of well-decomposed farmyard manure or leaf mould. Add 20 g of superphosphate at the base of the pit for good root growth. Planting can be carried out anytime during the year, but when adequate irrigation facilities are lacking, monsoon is the appropriate time for planting. While planting grafts, it is important to keep the graft-joint well above the ground. Once planting is done, regular watering is essential till the plants establish.

Pruning

          Like most tropical trees, avocado has a good natural shape and hence it need not be controlled by pruning. But selective and mild pruning of dead wood, basal branches touching the ground and very old devitalized branches which have seized to produce fruits may be attended to once the harvesting season is over. Severe or unnecessary pruning lowers yield by eliminating potential flowers produced on young branches at the periphery of the tree.

Manuring and fertilization

         Nutrient requirements of avocado vary according to variety, spacing and soil type. Before fertilizer application, the basin should be weeded and the fertilizer broadcast but not within 30cm radius of the trunk. After applying fertilizer, irrigation is useful if soil moisture is not adequate. Though it is difficult to specify exact dose common to all soils and varieties, a recommended fertilizer dose is given in   Table 1.

Table 1. A general recommendation of manures and fertilizers for an avocado tree

Tree age (years)	N* (g)	P* (g)	K* (g)	Farmyard manure (kg)
1–3	40	20	35	25
4–6	75	35	60	35
7–10	150	35	125	40
Over 10	200	45	165	50

* Expressed in the form of nutrient element.

 

           While, P and K deficiencies are less conspicuous, N and Ca levels in leaf markedly influence yield, fruit size and postharvest quality. The Mg, B and Fe are also important. The growers are advised to get the soil tested and consult soil specialist for specific recommendations. In California, healthy leaves of avocado Fuerte, have been reported to contain 1.8% N, 0.15% P, 1.5% K, 2.2% Ca, 125 ppm Fe, 50ppm Mn, 50 ppm Zn and 45ppm B.

Aftercare

          After planting, young trees must be watered and supported by stakes. To protect trees from sunburn, they should be provided with shade. Sometimes, the trunks of the young trees are whitewashed. To start with 60cm² basin around the plant is adequate, however, once in a while, size of the basin should be expanded with increase in the canopy size. Other aftercare operations involve regular watering during dry periods, occasional weeding, shallow digging of the basin so as not to injure the surface roots, removing of sprouts on the rootstocks (in case of grafted plants), attending to plant-protection measures and manuring.

            Intercropping in young orchards can be taken up by selecting a suitable vegetable crop as it gives additional income to the growers. Moreover, an intercropping system keeps the soil cool, adds organic matter, suppresses weeds, improves soil structure and may fix nitrogen. But these crops should not be raised very close to the avocado trees lest they compete with them for nutrients.

Irrigation

               Commercial avocado is successful if trees are regularly irrigated and the frequency should be adjusted depending on soil and weather conditions. The avocado trees show water stress suddenly by shedding fruits and leaves or by wilting as they have shallow root system. Loose and sandy soils require larger quantities of water than heavy soils. Generally in summer, trees should receive irrigation once in 10 days and adequate soil moisture after fruit set is necessary to sustain fruit growth, because any setback in growth is irreversible.

Harvesting and Postharvest management

             The regular harvesting commences from fourth year. Its fruits are harvested in August-September in south India. They should be plucked when they are fully mature which can be assessed by change in fruit colour, fruit size and sometimes the oil content. In Purple variety, fruits are plucked when they show a purplish blush, and in Green when they develop yellow tinge and once the glossy shine diminishes. If fruits are retained for longer periods, they drop before softening. Picking poles (with a net or cloth bag at the end) can be used for harvesting the fruits. Although a 25-year-old tree yields as high as 2,000 fruits, a yield of 400–500 fruits/tree is considered fairly good.

             Well mature avocado fruits ripen in 4–5 days after harvesting, but ripening can be accelerated by ethylene (10 ppm) treatment. Ripening takes place satisfactorily at 15°–21°C and is hampered above 30°C. Mature fruits can be held for a month at 6°–9°C coupled with 80–90% humidity. An extension of shelf-life can be obtained by storing at low temperature after enclosing the fruits in polyethylene bags. The ripening time of fruits stored is generally always less than the non-stored fruits. Packing is done in a single layer in well-ventilated wooden boxes so that they arrive in markets in good condition.