In this article we will discuss about the training and pruning of grapevine.
Training is a distinct process in grapevine and a number of different systems have been developed to create favourable microclimate to manipulate the physiology of the vine for increased productivity and fruit quality, and to give it a desired shape that maintains its vigour for a long period and facilitates requisite leaf exposure and different cultural operations including harvesting and plant protection.
Grapevine bears on new growth that emerges from the last season’s mixed buds. Pruning is necessary to regulate yield, size of bunches and quality of fruit. Proper pruning also regulates the number of buds and adequate number of bearing shoots each year, prevents the accumulation of old and unproductive wood and keeps the vine within manageable shape.
Training of Grapevine:
In nature, grapevine is a slender climber clinging with the help of tendrils and bearing scanty fruits at the tops. To domesticate it, channeling its energy from vegetative growth to enhanced bearing, an artificial support is a must. In fact, improper training may lead to complete barrenness of the vine.
Methods of Support:
Grapevine cannot be grown satisfactorily without some form of support, temporary or permanent, to obtain a well formed vine with strong straight trunk quickly and economically. Varied forms of support, viz., arbours (bowers), stakes and trellis have been devised and used, the first one being the most common in India.
The short time supports or stakes especially in hard-pruned vines provide support until the vines are large and rigid enough to stand on their own. The permanent supports, bowers and trellis are required for vines that are either cane- pruned or cordon trained. It is advisable to construct a durable bower or trellis before planting of vines to avoid frequent repairs or replacements.
i. Bower or Arbour or Pergola:
In spite of being the most expensive systems of support, this is commonly adopted for Thompson Seedless, Perlette and Anab-e-Shahi varieties. It is best suited in warmer climate where die vine grows vigorously. It provides good protection against hot desiccating winds. The bunches hang from the vines under the extensive vine spread and are saved from damage by birds and sun scorch.
It is also capable of giving high yield of quality fruit. The wood growth is suppressed due to shading effect as vines cover the overhead net completely. But the establishment of this system is rather tedious besides being expensive. The cost of establishment may range between Rs. 2.5 to 3.0 lakh per hectare at current price.
A bower consists of a crisscross network of wires usually 2.1 to 2.5 metres above ground and 30 to 45 cm apart, supported by pillars made of concrete, stone or iron, angle iron or even bamboo. For roof, strong angle iron of about 6.4 x 6. 4 x 0.64 cm section or steel ropes of 10 mm diameter are used to run on peripheral poles making a rectangle. Steel ropes perform better than angle iron. The wire used for making nets should be of 8 to 10 gauge according to the pressure to be sustained by the arbour.
Sometimes, holes are drilled in the angle iron arms at 60 cm distance to create a crisscross network of wires but it is not considered a good practice. Instead, the net wires should be fastened as such to the angle iron or steel rope at the periphery. If the wire sags, it can be restretched by twisting.
Each pillar is supported with a deadman fixed 100-150 cm deep in the ground which should be 15 x 30 x 60 cm in size in loamy soils and one and half times larger in sandy soils and should be made of reinforced cement brick concrete having a single steel bar of 12 mm diameter or of cut stone. The peripheral poles are kept inclined at 75° angle. The end poles are stretched with ropes made of 3 wires of 8 mm diameter, while each corner pole needs three such ropes.
ii. Trellis:
Although not used in tropical and subtropical regions, it may be of some worth in high hills. The most common types are two-wire vertical trellis and overhead trellis.
Three-wire vertical trellis once prevalent in north India was erroneously known as six-arm kniffin. Steel posts of about 6.4 x 6.4 x 0.64 cm sections and 2 to 2.5 m above ground are firmly fixed in earth with a cement concrete foundation. The end of posts are firmly anchored or braced.
The spacing of the poles depends largely on the planting distance. Two or usually three wires are stretched horizontally at the height of 1.2, 0.9 and 0.6 metre supported by single iron pole at 5 metres distance. The establishment cost of vertical trellis is about Rs. 1.5 to 2.0 lakh per hectare.
The telephone system or three-wire horizontal trellis or overhead trellis was used is north India for moderately vigorous varieties with more apical dominance. The poles are about 2 m high. All the wires run only in one direction and thus movement in the vineyard is unrestricted. The air circulation between rows was better and it was considered better than bower.
Y-Trellis is recently introduced in North India for higher yield and excellent fruit quality. Y-shaped structure is build up by maintaining 110° angle between the Y. The horizontal wires are stretched maintaining a distance of 9″ to 1′. This is an open canopy system allowing more sunlight and more aeration which leads to less buildup of humidity.
iii. Stakes:
These are commonly used in kitchen gardens where head system of training in practised. A good support may be a strong bamboo or a 5 cm diameter wooden pole of about 2 m height. The stakes should be charred over fire or treated at the bottom with solighum or coal tar to protect from white ants. The stakes are either fixed soon after or at the time of planting the vines keeping their 30 to 40 cm length in the ground to provide support till vine trunks gain strength to stand on their own.
The initial cost for providing stakes is high as the planting distance is reduced in head system to 2.0 X 1.5 m accommodating nearly three to four times more plants than in bower system. Not only the digging of more number of pits involves higher cost, the watch and ward of stakes and fruit is also expensive.
Training Systems:
The training systems were developed to suit the various needs, conditions and personal preferences. In Andhra Pradesh, Anab-e-Shahi vines were commonly trained on bower system. Bangalore Blue of Mysore was mostly trained to the mandap system. In Puna, Baramati, Phalton and Nagar areas of Maharashtra, two-wire trellis and bower systems were favoured but in Nasik and Marathwada regions, head system of training to a live stake of Pangara (Erythrina indica) was commonly followed.
In Punjab and Haryana, Anab-e-per predominant variety is mostly trained on bower and Y-trills and, to a limited extent, on horizontal and vertical trellis. Thompson Seedless and Black Prince varieties of grapevines were once trained on arbour with wires fixed on live poles of Kiluval (Commiphora candata) in Dindigul, Krishnagiri and Madurai. In Periyakulam, maximum yield from grapevine was obtained when trained on pandal system.
The choice of training system depends on factors, such as apical dominance, vigour of the vine, bearing zone on the shoots, soil type, cultural practices, economics of the system and prevailing climatic conditions.
i. Bower:
The training of vines, both under tropical and subtropical regions of India, is done by forming two major limbs on which several cordons are developed one on either side of each limb running along each wire. This is the most successful and popular system.
In the plains of north-west India, the grapevine undergoes sufficient chilling in winter while in summer the temperature may go as high as 43°C with very low relative humidity which prevent normal metabolism in the vine since most cultivars show little carbon dioxide assimilation beyond 35°C. In South India, high sunshine and low relative humidity occur during berry development and ripening. Bower system creates the required microclimate under the dense canopy of vines with a temperature difference of over 10°C compared to that in the open. More than 100 per cent increase in relative humidity has also been recorded under the canopy.
The two primary limbs (cordons) are developed bidirectionally and the secondary cordons are developed on the main arms so that the vine covers the overhead area of about 9 square metres when planted at 3 X 3 m. Short or long fruiting spurs are allowed to develop on the secondary cordons only. Being an extensive system, the fruiting area of the vine spreads over the entire nine square metres space which enables it to retain more fruiting wood than in other systems of training.
The formation of two primary limbs is sometimes encouraged by pinching off the apical shoot close to the wire. Two vigorous shoots growing in opposite directions are selected at the wire level for training as primary arms. These are allowed to grow upto to the length provided for the purpose. One secondary limb (cordon) is allowed to develop along each wire from these two primary arms.
Generally, the entire length of primary arms is attained in two years but will be better if it is achieved in three or even four years. Quick attainment of the length of primary limbs results in weak secondary cordon on the proximal parts of the main cordons and too much growth at distal parts.
In three metres, there are usually eight wires and, therefore, eight secondary cordons should be developed on either side i.e., approximately four on either side of primary cordon. Once the primary and secondary cordons have been developed, the rest of the pruning it is similar to that on any other cordon. It is customary to retain 100 to 200 fruiting spurs in Perlette and about 100 short canes in Thompson Seedless vine planted at 3 x 3 m distance.
On the basis of yield, bower system proved superior to kniffin system. Among several training systems in Beauty Seedless bower system was found to give the highest yield. Perlette, Muscat Hamburg, Himrod and Thompson Seedless bear much more heavily on bower system to more than compensate its high cost. Best growth, yield and fruit quality was obtained in Beauty Seedless grapevines trained on bower system.
Yields in Karachi Gulabi were the highest with bower system. In Beauty Seedless bower system gave 1.5, 1.9 and 3.1 times higher yields than telephone, kniffin and head systems, respectively. In Himrod, bower gave 1.6, 1.9 and 2.7 time’s higher yield than telephone, kniffin and head systems, respectively.
Bower system of training is most successful as it provides a unique microclimate, cuts excessive sunshine, increases the humidity and lowers the temperature under it, ensures maximum spread of foliage and best interception of light resulting in maximum yield and quality of fruit.
Harvesting is very easy and bird damage is much less. The system is difficult to adopt and requires lot of skill and labour, the cordons become barren if the vines are not trained and pruned properly, spraying and fruit haulage are difficult and the cost of establishment is much higher than in the other systems.
ii. Vertical Trellis:
If the main trunk extends horizontal on one side of the wire, it is termed as unilaterally horizontal cordon. When one cordon is trained to extend on either side of trellis making a T-type structure, it is termed as bilateral horizontal conrdon. The long trunk of the cordon enables good crop distribution.
The fruit quality is excellent because clusters do not touch each other and shoots do not rub against or grow through the clusters. Cordon system tends to make lower buds on canes more fruitful. Thus, varieties which bear on long spurs on head system will bear normal crop even on short spurs on cordon system. This system is simple and involves relatively lower cost.
In cordon trained vines, the height of wires from ground level varies depending upon agro-climatic conditions. Where it is intended to make use of ground heat and the cultivar is not vigorous, it may be as low as a few centimetres from ground.
After planting, one erect growing shoot is selected and the others are removed. This shoot is directed to grow along the horizontal wire and loosely tied with it. Side shoots arising on the upper side of the cordon are allowed to grow.
In Perlette, maximum intensity of anthracnose infection was observed on vertical trellis followed by horizontal trellis, bower and stakes in descending order. Anab-e-Shahi was noted most susceptible and Himrod least susceptible to anthracnose when trained on vertical trellis.
The initial training in these systems is expensive, laborious and requires more skill. The varieties which bear on long canes and have unfruitful basal buds cannot be trained on this system. The renewal of cordon is also difficult.
iii. Kniffin (Storey):
This system, first developed by William Kniffin in 1850, is being used, to some extent in India, in highly modified form named as Indian storey system. It is also called espalier system in some countries. In India, it was once believed to be good for varieties such as Thompson Seedless, Pusa Seedless, Black Prince and Muscat of Alexandria.
The training in this system is basically similar to that in cordon system. The permanent branches (arms) are arranged horizontally and tied loosely on the wires so that annual growth arises at the same level. The vines are trained to usually three and sometimes to two pairs of horizontal arms. On two wires, four-arm and on three wires, six-arm storeys are developed. Thus, there are no cordons and only four or six arms, one on each side of the main trunk running along each wire.
The maximum number of infected buds were found in Perlette (77 per cent) followed by Anab-e-Shahi (37 per cent), Himrod (34 per cent) and Thompson Seedless (17 per cent) when trained on Kniffin system. Perlette on Kniffin system was first to be infected by anthracnose and was rated moderately resistant whereas Anab-e-Shahi, although got diseased quite late, was more severely damaged. Thompson Seedless trained on this system had 28 per cent dead canes due to anthracnose infestation.
The fruit yield on this system was only about half of that in bower system. The overall developments of the vine and leaf area were much less because of under-utilization of space and the bird damage was more.
iv. Overhead Trellis (Telephone):
In this system, as the name suggests, the trellis looks like telephone wires. One or two tier trellis may suit semi-vigorous varieties. The young vines are supported by wooden sticks. After reaching the height of about 2 metres, the tip is pinched off to encourage side shoots close to the wires. Two vigorous shoots across wires are selected as primary arms from which six laterals, one on each side along the wires, are allowed to develop as secondary arms.
Vines trained on this system produce considerably higher yield than on vertical trellis but not as much as on bower. Similarly, higher yield in Himrod vines was recorded when trained on telephone system than on espalier (kniffin) and head systems. Its effect on bunch characters, maturity and quality of fruit in Beauty Seedless has been reported. Thompson Seedless vines trained on overhead trellis had lesser number of dead canes due to anthracnose than on bower.
Similar results were obtained in other cultivars also. Drooping of vine from the first and third wire forming a tunnel is conducive for the spread of diseases and bird damage. This method needs a lot of skill and expenses and is not suitable for varieties having low to moderate vigour. The system is best suited to the varieties which have comparatively lower vigour and bear fruit on basal buds of the canes, e.g. Beauty Seedless, Perlette and Delight.
v. Y-Trellis:
Vines are trained to H system of training. Vines are headed back at the height of 5 feet from the ground. Two secondary arms are developed on which fruiting canes are maintained. This training system is found highly suitable for Perlette and Flame Seedless. The system offers plenty of sunshine to the bunches and improve the quality of bunches. Grapevines on Y-trellis are spaced at 1.5 x 4 m which gives high yield, improves fruit quality and enhance maturity.
vi. Head:
The vines are supported by stakes during the first 4-5 years or till their trunks become strong enough. After planting, the growing shoot is cut at a height of about one metre. Four to five well placed branches arranged in the form of a goblet are selected. All the other side branches are pinched off. At the first pruning, the laterals are pruned to spur with one or two buds. These spurs will produce a number of shoots to provide arms for the framework.
At the subsequent prunings, a sufficient number of spurs are retained at the end of each arm in different directions for bearing as well as to provide canes for the next year’s spurs. Normally, 15-20 fruitng spurs of 3-4 buds and an equal number of renewals of one to two buds are retained on a vein. But, as in other system, the renewal spurs put forth only a weak growth or die and arte of no use.
The head system is considered the most economical. But, the cost per unit production of grapes was highest with this system. Berry size is usually bigger. The maximum bud and flower drop was noted in Beauty Seedless on head System. Disease intensity on both leaves and canes was the lowest in this system.
Thompson Seedless vine trained on this system had the least number of dead canes due to anthracnose infection. The yield on head system is very low. On an average, the vines at full bearing yield only 4-5 kg fruit. This system is not suitable for vigorous varieties pruned to long canes which do not bear on basal buds. In windy location, the vines trained on head system are likely to lodge. Installation of stakes costs a lot and requires watch and ward.
Apart from these, other systems of less significance are also followed in certain areas e.g., factory system employed in South Africa. Guyot system of training is followed under conditions where the temperature is very low during the fruit development and maturity.
Chautauqua system is followed for long bearing varieties as Sultanina and Corinth. Fan system is suggested for extreme cold conditions and is suitable for cultivars bearing on long canes e.g. Thompson Seedless. Umbrella system is suitable for Thompson Seedless, and Black Corinth. Tatura trellis is followed for training grapevines in Australia.
Pruning of Grapevine:
Pruning comprises the removal of living canes, shoot, leaves and other vegetative parts of the vine. In nature, grapevine shows acropetal growth and if left as such its branches continue to elongate climbing with the help of tendrils.
Acropetal growth is more pronounced under warmer condition. When pruned keeping 8-10 buds, only the terminal 2 or 3 nodes usually put forth growth and those at proximal positions either do not sprout or produce only weak shoots bearing small bunches that do not ripen.
Vine pruning regulates or encourages good yield and improves size and quality of fruit. The aim of pruning is to properly distribute the bearing wood over the vine and to regulate the crop maintaining its vitality for consistent productivity. Generally, pruning has a depressing effect on vine growth and reduces bearing. However, over-bearing also has similar effect and delays the ripening.
Pruning Methods:
(i) Spur Pruning:
The retention of 1-4 basal buds after pruning as fruiting canes is called spur pruning. For the most economical production of all varieties of grapes that produce medium sized clusters on shoots arising from buds at the base of the canes, spur pruning should be used. Perlette variety is spur pruned.
(ii) Cane Pruning:
It is practised by leaving more than four buds on a cane. It should be used with varieties of which the lower buds on the canes are usually sterile such as Thompson Seedless.
(iii) Mechanical Pruning:
Cane pruning with less number of canes per vine of same length is being used for more varieties. It permits positioning of the fruit for machine harvesting better than the other system.
Type of Pruning:
1. Dormant Pruning:
The principal pruning is done while the vine is dormant, between leaf fall in autumn and the starting of the buds in spring.
Time of Pruning:
In North West plains, the pruning is generally practised from middle of January to first week of February when the vines are in dormant condition.
In tropical areas of Maharashtra, Andhra Pradesh, Karnataka, and Tamil Nadu, the vine continues growth all the year round and does not undergo dormancy. Pruning is, therefore, done twice a year, once in summer and again in winter. Summer pruning is done during March-April, except Tamil Nadu, where it is done in June when the canes are cut back to 1- 2 buds to induce vegetative growth and is called back pruning or growth pruning. During winter, pruning is done between the last week of September and first week of October in northern districts of Karnataka and in December in Tamil Nadu when it is done to induce fruiting depending upon the variety.
Amount of Pruning:
Amount of pruning depends on the bearing behaviour of different cultivars. Number of canes per vine and number of buds per cane varies from variety to variety.
Unit of Pruning:
When a vine has reached the stage of full bearing, pruning consists of removing all the growth except:
(i) Bearing Units:
For the production of fruit and new wood or fruit only,
(ii) Renewal Spurs:
For renewal or the production of wood for the next year and
(iii) Replacement Spurs:
In the older vines, for the replacing or shortening of arms.
2. Summer Pruning:
Summer pruning, of which there are many forms, consists in removing buds, shoots, or leaves, while they are green herbaceous. Thus, it is done while the vine is growing or active.
Summer pruning has various uses, principally as follows:
(a) Correction of Shape:
To direct the growth into the parts that will form the permanent frame work of the vine such as the trunk, branches and arms and to keep these parts active and healthy. This is accomplished by such operations as disbudding, pinching and suckering.
(b) Shading the Fruits:
To increase the shade on the fruit by topping which, promotes the upright position of shoots and growth of laterals.
(c) Opening the Vine to Light:
To, open the vines and thus expose the fruit more favourably to light and air.
In Punjab, summer pruning was substituted by three summer pinching, one in May and two in August – September to increase fruit yield and quality since the former is a cumbersome process.
Rejuvenation and Top-Working:
The old Perlette vines trained on bower system can be successfully rejuvenated by heading back the primary arms leaving behind 1′ stubs in the month of December – January. Bordeaux paste should be applied after heading back of primary arms.
Flame Seedless variety can be successfully top-worked on Perlette vines. For this purpose, tongue grafting should be done in the last week of February on one year old shoots (canes). This technique advances maturity by 4 – 5 days of Flame Seedless. The fruit quality is also improved.