The following points highlight the top five cultural practices of grapes. The practices are: 1. Irrigation 2. Intercropping 3. Weed Management 4. Manuring and Fertilization 5. Nutrient Requirements.
1. Irrigation:
The growth and fruit production of grape vine is directly associated with the presence of water throughout its life. The yield from a vineyard is an end product of a series of biochemical and physiological processes that take place in living cells of grapevine. These processes proceed at maximum only when turgor pressure of cells is optimum.
The excessive depletion of soil would bring about corresponding increase in diffusion pressure deficit within the tissue fluid of the vine. Consequently, the growth is affected adversely. The root elongation ceases when the turgor pressure approaches zero.
The dormant mature vines exhibit a high degree of tolerance to waterlogged soils. But these are prone to damage if subjected to waterlogged conditions for a long period during active growth season. The roots of grapevine in saturated soil may die from lack of aeration.
The remaining fewer healthy roots are not able to absorb sufficient water to meet the needs of the vine even from the very wet soil. The saturated soil conditions also cause reduction in microbial activity and leaching of nutrients.
The grapevine under excessive soil moisture conditions may tend to produce excessive vegetative growth at the expense of fruiting. Also, the vines will continue to grow or initiate new vigorous growth after harvest if readily available water is in ample supply. Such a late growth utilizes carbohydrates and does not allow their storing.
The late growing new shoots fail to mature properly and are subject to injury by frosts. Such vines are likely to show bud failure and less crop in the following year than the vines that ceased growth early and matured their wood well. This situation is more pertinent to the cane pruned varieties.
Under the Punjab conditions, one irrigation is suggested after pruning in the first fortnight of February. The second irrigation is applied in first week of March. After fruit set in April till first week of May, the irrigation is recommended at 10 day intervals. Vineyards are to be irrigated weekly during rest of May.
The interval is decreased to 3-4 days during June. During July to October, the irrigation is given if there is prolonged dry spell or insufficient rainfall. Only one irrigation is recommended from November through January, if the soils get extremely dry.
The grapevine needs regular irrigation in southern India except at the time of pruning and monsoon. Irrigation is given at 6-8 days interval during fruiting period. In Madurai, the vines are irrigated four times a week during summer and two times a week during winter.
The irrigation timings should also be based on the requirement of the vines at the critical stages of bud burst, flowering and harvest. Other irrigations should be arranged to provide a reasonable moisture supply between these times.
The water needs of vineyard are influenced by the following factors:
(a) The time to irrigate, the number of irrigations and the amount of water at each irrigation are determined by the age and condition of the vines and soil type. The climatic factors such as temperature, humidity and wind influence greatly the water needs of vineyards.
(b) Young vines need more frequent irrigation than grown up vines. The vines trained on bower system need more water than those on kniffin or telephone or head system.
(c) The irrigation is seldom applied during winter when the vines remain dormant. Hence, the soil moisture depletes to a very low level. As such, vines would not resume normal growth in spring unless irrigation is applied to replenish the soil moisture. Irrigation soon after pruning hence is necessary.
(d) The period between fruit set and maturity is the most critical. Adequate water should be available to vines during the period.
(e) During the hot period from mid-May to mid-June, there is great need of water. The sugar accumulation in berries occurs during this period.
(f) Irrigation should be with-hold a little ahead of fruit maturity. This improves the fruit quality.
(g) Irrigation should never be ignored after harvesting of the grapes.
According to estimates made in Uzbekistan, 1.5 per cent of the water is used from beginning of growth to flowering, 10 per cent between beginning of flowering and fruit set, 43 per cent during fruit growth and 45 per cent during ripening. It is, therefore, essential that the amount of irrigation water is regulated according to the stage through which the plant is passing.
2. Intercropping:
Actually no intercrop should be sown in vineyards as it comes into bearing one year after planting and commercial crops start after 2-3 years of planting. Apart from this, the distance between vines is 3 x 3 metres and as such much space is not left between the plants for growing of intercrops.
Another factor is that almost entire plantations are trained on bower system of training. This structure with the spread of grapevines on it causes partial to complete shading in the 3rd year. Also, the grapevine is a shallow rooted crop; therefore, root injury is quite possible in case of deep ploughing.
Keeping in view the above facts, intercrops should not be grown in the vineyards. But it has been observed that grape growers have started planting of intercrops like radish, cucurbits, bhindi, brinjal, cabbage and potato for the first two to three years after planting the vineyards. Short duration crops like cucurbits are planted during summer months when irrigation can be applied to these intercrops along with grapevine without any loss.
However, to augment organic matter in the soil, it is better to grow cover crops of leguminous types like guara, senji and cowpeas and bury them into the soil, while they have attained maximum vegetative growth. The purpose is to keep the soil loose and friable. Exhaustive and tall crops should never be sown.
The winter season vegetables like cabbage, cauliflower and peas should not be grown during dormant period because they disturb the vineyards. By giving irrigation to these vegetables during winter, the vines would continue to put some growth which affects very badly in the next cropping. Only, the short term intercrops like moong and mash can be sown during the first two-three years.
3. Weed Management:
The vineyards are infested with weeds which compete with the grapevine for water and food. Also they harbour the harmful insect’s viz. defoliating beetles, stem girdler and the jassids. These insects hide in underneath and subsequently emerge to attack the vines when the conditions are favourable for them to do so. The weeds root secretes toxins which adversely affect the vine growth and fruit bearing. Cultivation is effective if done frequently but it may reduce yields from root pruning and cause effect on soil moisture.
Moreover, hand weeding is labour intensive and costly, owing to the steady increase in labour wages and their non-availability. Weed management had become an expensive input in the cultivation of grapes. Recently, the control of weeds through the use of chemicals has come to light which is not only economical but also convenient and efficient as it consists of one or two applications.
Hexuron 80 WP (diuron) @ 3.0 kg/ha (first fortnight of March) after thorough cultivation to remove the established growing weeds/plant debris can effectively control the weeds when applied at pre-emergence stage or glycel 41 SL (glyphosate) or gramoxone 24 WSC (paraquat) @ 4 1/ha as post-emergence should be sprayed when the weeds are growing actively and attain die height of 15-20 cm. Dissolve the herbicides in 500 litres of water per hectare so as to give a thorough coverage to the weeds in the field.
Spray glycel/ gramoxone during the calm day to avoid spray drift to the foliage of the grapevines. Total uptake of nitrogen, phosphorus and potassium by weeds per unit area in vineyards was significantly more in control than other treatments which show that there was a positive correlation between weed population and nutrient uptake by weeds. The fruit yield was recorded higher under glycel treatments. The quality of fruits in terms of total soluble solids was improved with hexuron and glycel treatments.
4. Manuring and Fertilization:
It is basically essential to know the role of different nutrients on growth, fruit yield and quality in order to include them in various proportions in vineyard manuring at different stages of growth and fruit development.
a. Nitrogen:
Nitrogen was found to have a role in the flowering of grapes. Absence of Nitrogen in the fertilizer was found to delay the floral initiation in Anab-e-Shahi. It was also found to have influence on the number of bunches per vines and the mean bunch weight ultimately increasing the yield per vine.
The need of this element is greatest and the response is most rapid on sandy gravelly soils. On heavier soils, nitrogen availability and response will occur more slowly. Crop yield may be reduced before the deficiency symptoms of this element appear.
b. Phosphorus:
Phosphorus appears to have a clear cut role in the floral bud initiation. Application of phosphorus was found to promote fruitfulness in Anab-e-Shahi vines. Increasing levels of applied phosphorus were associated with increased fruit yield in Anab-e-Shahi and Thompson Seedless.
c. Potassium:
Potassium was found to be favourable for the inflorescence formation. Its application made those buds fertile which under normal conditions remained sterile through increased carbohydrates accumulation. Increased yields were obtained with increasing levels of K in Anab-e-Shahi and Thompson Seedless grapes. Potassium was reported to have an important role in the quality of grapes. Higher level of applied K was associated with higher total soluble solids content of grape juice.
The deficiency of this element has been associated with vineyard areas with very sandy soils. Potassium fertilizer must be placed near the active root zone. Measurable response to K fertilizer has only been obtained where visual deficiency symptoms have appeared.
d. Magnesium:
Magnesium requirement of vines is more during berry ripening. Mg deficiency is very common in the vineyards of peninsular India, particularly in Anab-e-Shahi. The deficiency is mostly induced due to over manuring with potato and is more prevalent in light sandy soils. Thus, Mg requirement is more during fruit development stage and in low Mg soil, it moves from leaf chlorophyll to the developing fruit causing chlorosis.
e. Calcium:
Deficiency of calcium makes the berry skin susceptible to necrosis and rotting. Higher levels of petiole calcium were associated with reduced yields in Anab-e-Shahi and Thompson Seedless. The exact role of Ca in vine production is, however, not clear.
f. Micronutrients:
Among the micronutrients, boron, zinc, iron, manganese and copper are important in viticulture. Boron is essential for the regulation of carbohydrate metabolism. It is also important for the pollen germination, growth of pollen tube and normal fruit set. Its deficiency is commonly known as hen and chicken disorder of the clusters.
Boron is considered to be delicate among the micronutrients because of the narrow range between its statuses of deficiency or excess. Shoot growth, bunch and berry size and sugar content of the juice was found to increase with boron application in Perlette grape.
Boron spray increased the protein and RNA contents of grape leaves. Thus, it seems to improve productivity and quality in grapes. Boron deficiency can be corrected by either soil application or foliar sprays of boron containing materials like boric acid or borax.
Zinc deficiency symptoms start appearing in the mid-summer when secondary or auxiliary growth begins. The secondary growth and the primary shoot tips are affected first. The main foliage symptoms of zinc deficiency are the chlorotic pattern, the location and the small size of affected leaves and particularly the widened angle formed between the two basal lobes of the leaf blade when the petiole is attached there, the primary veins tend to draw together, resulting in a fan like appearance. Foliar application of zinc improves vine growth, fruitfulness, fruit set, fruit yield and quality of berries.
Iron is needed for the activation of several enzyme systems. Its deficiency impairs chlorophyll production resulting in the characteristic chlorosis of the young leaves. Deficiency of Fe is common in calcareous soils and in vines with weak root systems. Beneficial effects of iron on vegetative growth, fruit yield and quality of berries were reported. The concentration used ranged between, 0.05 to 0.2 per cent iron sulphate.
Magnesium serves as an activator for enzymes in growth processes and helps in chlorophyll formation. Therefore, its deficiency manifests in leaf chlorosis which is common in acidic sandy soils. The deficiency can be corrected by spraying 0.2 per cent neutralised manganese sulphate as soon as the deficiency symptoms appear on the vines.
5. Nutrient Requirements:
Under the Bangalore conditions for Anab-e-Shahi vines of less than 5 years age, a combination of 500 kg N, 125 kg P2O5 and 750 kg K2O per hectare per year was found to be optimum. While the optimal combination for the vines of more than 5 years of age was found to be 500 kg N, 500 kg P2O5 and 1000 kg K2O per hectare per year.
Individually, N at 1000 kg, P2O5 at 500 kg and K2O at 800 kg per hectare were found to be optimum under western Maharashtra conditions. Under Southern Karnataka 666 kg N, 888 kg P2O5 and 666 kg K2O per hectare were found optimum doses.
In Punjab, to one year old grapevine 20 kg farmyard manure, 400 g urea, 1.5 kg superphosphate (16% P2O5) and 250 g muriate of potash are recommended. To full grown vine of 5 years and above, 80 kg farmyard manure, 1 kg urea, 4.5 kg single superphosphate and 800 g muriate of potash is added. To newly planted vine apply 60 g urea and 125 g muriate of potash in April and repeat the same dose in June.
Time of Application:
Under Maharashtra conditions where vines are pruned twice, application of 60 per cent of annual dose of N, 50 per cent of P2O5 at April pruning and rest of N and P2O5 and the entire K2O at October pruning is recommended. Application of P after 30-40 days after pruning was found to promote fruitfulness in Anab-e-Shahi vines.
Irrespective of the time of application, K was found to promote bud fertility. Application of K on 20th day after pruning improved the fertility status of promixal buds, while application on 50th day in the distal region. Early application of N i.e., 20th day after pruning and later application of P and K 35-50th day after pruning, was found to favour fruit bud differentiation.
In Punjab, the whole quantity of farmyard manure, superphosphate and half nitrogen and half potassium is applied after pruning. The remaining nitrogen and potassium is applied in April. The use of high dose of fertilizers results in excessive vegetative growth and barrenness.
In the case of bower system, complete shade under the bower is an indication of excessive growth. In that case, the nutrient content of the soil should be re-checked with a soil test and the fertilizer dose be adjusted. Give two sprays of urea @ 1% first at full bloom and second at fruit set to get higher yield and better fruit quality in Perlette grape.
Foliar Application:
Application of nutrients through foliage is yet another method to increase the efficiency of applied nutrients. It overcomes the soil and translocation factors in the absorption of nutrients and envisages at greatest economy of the nutrients. Foliar application of N as urea, P as calcium phosphate and K as potassium chloride resulted in the increased contents of N, P and K for improving the yield and quality of the fruit.