High Density Planting in Pineapple

international market. A few decades ago, the planting density followed for pineapple in India were only fifteen to twenty thousand plants per hectare, with a productivity of less than twenty thousand tones fruit per hectare, resulting in high cost of production. Under such low density planting, 20 to 25 % fruits become unmarketable due to sunburn in the tropical region. Therefore, extensive studies were undertaken at the Indian Institute of Horticultural Research, Bangalore, during the 1970’s and 80’s to develop high density planting of pineapple for increasing the productivity and fruit quality and reducing the cost of production. These studies proved the benefits of increased planting density in the range of 53,000 to 63,500 plants per hectare.

Two-row trench system of planting has been found to be the best for high density planting in the plains, whether the crop is grown with or without irrigation. The field is laid out into 22.5 to 30.0 cm deep trenches alternating with mounds. In each trench, two shallow furrows about 10 to 15 cm deep and 15 cm inside from the edge of the trench are opened and suckers or slips are planted in these furrows, so arranged that two plants will not be exactly opposite to each other. Spacing of pineapple plants depend on the growth of the plant. Soil moisture and fertility influences plant growth and indirectly determine spacing required per plant and eventually planting density. In overall analysis, plant-to-plant spacing of 22.5 to 25.0 cm and row-to-row spacing of 45 to 60 cm are ideal. Where pineapple plants grow luxuriantly with long leaves, a wider spacing of 90 cm between the trenches is required, but in places where growth of the leaf is moderate, a trench-to-trench spacing of 75 cm is adequate. A plant density of 63,000 plants/ha (22.5 cm x 60 cm x 75 cm) has been found ideal in semiarid mild tropical areas. In hot and humid tropical areas, plant density of 53,000 plants/ha (25 cm x 60 cm x 90 cm) performs well. However, decrease in fruit weight was quite evident when plant-to-plant spacing was reduced to 20 cm and row-to-row to 40 cm irrespective of the spacing between beds.

Initial establishment of planting material in the field is important to avoid gaps and the subsequent poor growth of replants under the competitive situation of high planting density. Suckers weighing 500-600g and slips weighing 350-400g are the best for initial field establishment under high density planting. July-August is found to be the best season of planting for establishment and growth of plants. To avoid any reduction in fruit size to unmarketable levels due to interplant competition for plant nutrients, nutrient management of high-density orchards need to be done more scientifically than under low-density planting, to meet the requirements of each and every plant. Nitrogen at 12g under irrigated and 16g under rainfed conditions along with potash at 12g per plant is recommended for the plant crop. For irrigated and rainfed ratoon crops, 10g nitrogen and 12g potash are recommended per plant. Ammonium sulphate is the best source of N

The yields recorded under high-density planting are in the range of 85 to105 tones/ha, which are 55 to 85 tones more than the conventional planting densities, without adversely affecting the fruit size, quality and canning recovery. It is associated with other advantages like less weed infestation, protection to fruits from sunburn and increased production of suckers and slips per unit area, and non-lodging of plants. Close planting also saves on the upright orientation of the apical leaves, and eventually results in uniformly coloured lustrous fruits, which are cylindrical with low taper ratio, giving more canning recovery. Another advantage of high-density planting is the overlapping of basal leaves forming a sort of natural covering over the soil, preventing evaporation losses and thereby resulting in moisture conservation. Under dense planting a microclimate with high humidity will be created around the plant, which is congenial for growth and fruiting. Two successive ratoon crops harvested at twelve monthly intervals amounted to 50.7 and 53.8% of the plant crop yield at high-density planting under good management. Highest cost : benefit ratio of 1: 4.2 was observed in planting densities of 53,000 and 59,200 plants/ha.