![Pruning Practices
A critical consideration for tropical and subtropical fruits is also the timing of
pruning.
If pruning or girdling occurs at a time that promotes vegetative growth at the
expense of fruit growth, a Ca imbalance and reduction in overall fruit size may
occur.
Girdling (a commercial practice in which the phloem of the tree or vine is
removed) 4 to 6 weeks before harvest can increase peach and nectarine fruit size
and advance and synchronize maturity.
Higher fruit Ca levels during the first 8 weeks of ‘Hass’ avocado fruit growth when
the spring vegetative flush was controlled with the growth regulator β-[(4-
chlorophenyl)methyl]-α-(1 ,1-dimethyl)- 1H l, 2,4-triazole-l-ethanol (paclobutrazol).](https://image.slidesharecdn.com/l-7preharvestoperations-240611174258-468de698/85/L-7-Pre-harvest-operations-kkkjjjjpptxkkk-8-320.jpg)
L-7 Pre harvest operations.kkkjjjjpptxkkk
- 1. Preharvest operations to extend shelf life of fruits and vegetable crops
- 2. Cultural Practices Soil type, rootstock, mulching, irrigation and fertilization influence the water and nutrient supply to the plant, which can in turn affect the nutritional quality and shelf life of the harvested plant part. Good horticultural practices (GHP) ensure good yield, and ultimately the postharvest life and quality of produce.
- 3. Pre harvest Operations Climate/environment Rootstock/scion Planting design Pruning practices Irrigation Fertilizer application Agricultural chemicals Plant growth regulators Canopy manipulations
- 4. Climate / Environment Environmental factors include climate (temperature, wind and rainfall), air quality, and positional effects both within a planting and within the tree. Elements such as wind, heavy precipitation, and frost may result in direct loss of the fruit from the postharvest chain due to fruit scarring Increased incidence of plant pathogens associated with high rainfall, especially during flowering (i.e., anthracnose) and loss of fruit related to freeze damage. Temperature during fruit growth and maturation may also influence fruit quality by either hastening or delaying horticultural maturity.
- 5. Cultivar and Rootstock Genotype Cultivars: The quality of seed or plant material is an important factor that controls the quality of the fruit and vegetable produced. Several parameters of quality are controlled genetically. Cultivar and rootstock genotypes have an important role in determining the taste, quality, yield, nutrient composition and postharvest life of fruits and vegetables. The incidence and severity of decay, insect damage and physiological disorders can be reduced by choosing the correct genotype for given environmental conditions.
- 6. Breeding programmes are constantly creating new cultivars and rootstocks with improved quality and better adaptability to various environmental and crop pest conditions. Some experts consider the most important cultivar characteristic for fruits and vegetables to be disease resistant including resistance to diseases that diminish postharvest quality. Control of some postharvest diseases may include breeding for resistance to the vector (eg. aphid, nematode, leafhopper and mite), rather than just for the pathogen.
- 7. Planting Design It affects both the quantity and quality of the produce. High density planting increases competition between plants, reduces light availability, and thus may decrease quantity. Low density planting lead to large size, better colored fruit or vegetable which may have shorter shelf life. Larger fruits are commonly more sensitive to physiological disorders.
- 8. Pruning Practices A critical consideration for tropical and subtropical fruits is also the timing of pruning. If pruning or girdling occurs at a time that promotes vegetative growth at the expense of fruit growth, a Ca imbalance and reduction in overall fruit size may occur. Girdling (a commercial practice in which the phloem of the tree or vine is removed) 4 to 6 weeks before harvest can increase peach and nectarine fruit size and advance and synchronize maturity. Higher fruit Ca levels during the first 8 weeks of ‘Hass’ avocado fruit growth when the spring vegetative flush was controlled with the growth regulator β-[(4- chlorophenyl)methyl]-α-(1 ,1-dimethyl)- 1H l, 2,4-triazole-l-ethanol (paclobutrazol).
- 9. Irrigation Growing plants need a continuous supply of water for both photosynthesis and transpiration Some of the Bad effects 1.Too much rain or irrigation, which can lead to brittle and easy damage in leafy vegetables and to increase the tendency to decay. 2.Lack of rain or irrigation, which can lead to low brittle and easy damage in leafy vegetables and to increased tendency to decay. 3.Dry conditions followed by rain or irrigation, which can give rise to growth cracks or secondary growth in potatoes or to growth cracks in tomatoes
- 10. Examples Irrigation effects on postharvest fruit quality are difficult to quantify. Pre harvest water stress influenced polyphenol oxidase (PPO) levels in ripe avocado fruit after 30 days in storage at 5.5°C. PPO has been associated with meso carp discoloration in avocado. In Bartlett pear, increased tree water stress was associated with increases in fruit TSS, firmness, and yellow fruit colour and in decreased fruit size and vegetative growth. In tomatoes, water stress at the end of the season, which may be achieved by irrigation cut off or deficit irrigation relative to evapo- transpirative demand for generally more than 20 days prior to harvest, may markedly improve TSS .
- 11. Melon postharvest quality is also quite sensitive to water management. Over irrigation can result not only in low TSS in melons but also unsightly ground spots and fruits rots Rapid growth resulting from irrigation following extended periods of soil water deficits may result in growth cracks in carrots, potatoes, tomato and several other vegetable crops. Uneven irrigation management may also increase the incidence if “spindle”-or “dumb-bell” shaped potatoes, depending on the growth stage during which soil water was limited.
- 12. Application of fertilizers Lack of plant foods in the soil can seriously affect the quality of fresh produce at harvest. On the other hand, too much of fertilizers can harm the development and postharvest condition of produce. 1.Lack of nitrogen can lead to stunted growth or the yellow-red dis colouration of leaves in vegetables e.g., cabbage. 2.Lack of potash can bring about poor fruit development and abnormal ripening 3.Calcium-moisture imbalance can cause blossom-end rot in tomatoes and bitter pit in apple 4.Boron deficiency can lead to lumpiness in papaya, hollow stem in cabbage and cauliflower and cracking of outer skin in beets.
- 13. Agricultural chemicals Pesticides and herbicides are used as sprays or soil applications to control weeds, disease and insect pests. They are dangerous because they can damage produce by producing spray burns if used incorrectly and they can leave poisonous residue on produce after harvest. In most countries, there are laws to control the use of pesticides, which should be used only in recommended concentrations. Strict observance of the recommended delay between the last spraying and the harvesting is required in order to keep poisonous spray residues from reaching the consumer. Advice on regulation should come from extension or other agricultural department officers.
- 14. Plant Growth Regulators PGRs are organic substances, other than nutrients, which in small quantities promote, inhibit, or otherwise modify various plant physiological processes. Every physiological process in the plant can be said to be the result of a delicate balance between such PGRs. Naphthalene Acetic Acid (NAA) are used for thinning blossoms in apples. Gibberellic acid are used to increase fruit size in grape and to maintain rind integrity in citrus. Ethephon is used as a pre harvest spray to induce ripening in some crops such as tomato.
- 15. PGR Commodity Concentration Usage 2,4 - D Citrus, Mango Limes, Lemon Mandarin 5-25 ppm 50-100 ppm 12 ppm Control of fruit drop Extending shelf life Reduces granulation Cytokinin Lime and Lemon 10 and 25 ppm Extend shelf life Ethephon Bael Ber Date palm Grapes Peach cv. July elberta Persimon cv. Hachiya 1000 ppm 750 ppm 1000 ppm 100 ppm 300 ppm 500 ppm 25 ppm Ripening can be advanced by 45 days Induces early maturity Advances maturity Reduce uneven ripening Fruit thinning Salicylic acid Sweet cherry 2 mM Induced disease resistance and reduced disease incidence Use of plant Growth regulators (PGR) for enhanced shelf life and postharvest quality
- 16. Ethrel Mandarin 50 ppm Promotes dehiscence of hulls Ethylene Avocado Banana, Mango, papaya 10 ppm 100 ppm Colour enhancement and enhancement of ripening GA Grapes Grapes grapes jamun litchi 10 ppm 40 ppm 60 ppm 60 ppm 40 ppm Degreening Accelerate ripening Uniform ripening Cluster elongation Berry thinning Increasing berry size Control of flower and fruit cracking and Sprouting inhibition
- 17. NAA Apple, Apple Apricot Grapes Pineapple Pineapple 10-20 ppm 10 ppm 25-50 ppm 50 ppm 10-20 ppm 200-300 ppm Fruit thinning Control of pre harvest fruit drop Fruit thinning Minimize postharvest berry drop Induction of uniform flowering Increasing fruit size by 15-20 per cent Increasing fruit size Paclobutrazol Loquat 500 ppm Increasing fruit size Promalin Apple 30-60 ppm Improving oblong shape of delicious apples Putrescine Peach 5-20 mM Reduced ethylene production, delayed softening, and retained titrable acidity Salicylic acid Sweet cherry 2 mM Induced disease resistance and reduced disease incidence
- 18. Canopy manipulations Crop load In most fruits, fruitlet thinning increases fruit size while also reducing total yield; a balance between yield and fruit size must be achieved. Maximum profit does not occur at maximum marketable yield since larger fruits bring a higher market price. For example, leaving too many fruits on a tree reduces fruit size and SSC in the early- ripening May Glo nectarine and the late – ripening O’ Henry peach. Crop load on O’ Henry peach trees affected the incidence of internal breakdown measured after 1, 2 and 3 weeks at 5°C (41°F). Despite a large amount of mealy fruits in all lots, the overall incidence of mealiness and flesh browning in fruit from the high crop load was low, intermediate in fruit from the commercial crop load and the highest in fruit from the low crop load.
- 19. Fruit canopy position Peaches grown under a high light environment (outside canopy) have a longer storage and market life than peaches grown under a low light environment (inside canopy). The use of more efficient training systems that allow sunlight penetration into the center and lower canopy areas is recommended to reduce the number of shaded fruit. In kiwifruit, shading reduces fruit count rather than individual fruit weight, delays harvest maturity, decreases SSC and accelerates the rate of fruit softening during storage.
- 20. In grape vines, open canopies and optimal air circulation can be attained by the proper combination of plant spacing, vegetative thinning and training. Vine vigor can be controlled by stem training and by avoiding high levels of nitrogen. This improves light penetration to leaves, ensuring that they continue to produce photosynthesis and do not prematurely senesce and become pathogen hosts. An open canopy lowers the humidity around the plant, reduces wetting improves foliar nutrient application. An open canopy also enables the pickers to harvest more rapidly, decreasing the likelihood of overripe fruit.
- 21. Leaf removal Summer pruning and leaf pulling around the fruit increases fruit light exposure and, when performed properly, can increase fruit colour without affecting fruit size and SS. Excessive leaf pulling or leaf pulling has done too close to harvest, however, can reduce both fruit size and SSC in peaches and nectarines.
- 22. Crop rotations Crop rotation may be an effective management practice for minimizing postharvest losses by reducing decay inoculation in a production field. soil borne fungi, bacteria and nematodes can build up to damaging levels with repeated cropping of a single vegetable crop, rotations out of certain vegetables are commonly recommended in intensive vegetable production regions. Four-year rotations with non cucurbit crops are routinely recommended for cucurbit disease management, as are 4-year rotations for garlic to decrease postharvest disease incidence.