Everything you need to learn about cultivating walnut organically. Learn about:- 1. Introduction to Walnut 2. Climate and Soil Required for Cultivating Walnut 3. Propagation, Rootstocks and Management Practices 4. Planting and Spacing 5. Training and Pruning 6. Nutrient Management 7. Potential for Enhancing Total Production 8. Harvesting 9. Varieties.
Contents:
- Introduction to Walnut
- Climate and Soil Required for Cultivating Walnut
- Propagation, Rootstocks and Other Management Practices of Walnut
- Planting and Spacing of Walnut
- Training and Pruning of Walnut
- Nutrient Management of Walnut
- Potential for Enhancing Total Production in Walnut
- Harvesting of Walnut
- Varieties of Walnut
1. Introduction to Walnut:
Walnut (Jugulans regia) is one of the most important nut crop grown in temperate region and produces edible nuts having higher nutritional value. It belongs to the family Juglandaceae. It is monooecious and cross-pollination is through wind. The nuts are rich in protein, oil, vitamins and minerals. Walnut is indigenous to the region from Persia to Kashmir.
In India, it is grown since the time immemorial especially in north-western Himalayas in the states of J&K, HP and Uttarakhand at an elevation of 1200 to 2150 m above mean sea level. In India there are no systematic orchards of walnut and trees of seedling origin are grown which exhibit wide interspecific diversity in plants, foliage, floral, nut and kernel characters. Present area under walnut has increased to 1,22,650 hectares (2012-13) compared to 61,872 hectares in 2001-02.
Similarly production level of walnut has increased to 2,33,120 tons in 2012-13 compared to 86,263 tons in 2001-2002. The productivity level has also enhanced to 1.8 tons/ha in 2012-13 compared to 1.39 tons/ha in 2001-02. This clearly shows that farmers have started adopting high yielding clones and improved cultivation practices.
2. Climate and Soil Required for Cultivating Walnut:
The main climatic limitation for walnut cultivation is, spring frost, extreme summer heat and insufficient winter chilling. The plants can tolerate up to -11°C during deep dormancy, but after the commencement of growth, the temperature of even 2-3°C below freezing point kills leaves, shoots and flowers thereby resulting in total crop failure.
Walnut requires a certain period in winter to break dormancy for satisfactory growth and flowering. Lack of chilling requirement may result in irregular and delayed bud opening and blossoming, resulting into poor crop and death of shoot tips. The chilling requirement varies with cultivar from 700 to 1500 hrs. Cultivars/races differ in their tolerance to frost.
On the other hand, high temperature is also harmful which causes sunburns of hulls and shriveling of kernels leading to the production of empty nuts. Also lower summer temperature is not favourable for filling of nuts. Temperature of 29-32°C near harvesting time favours good kernal development. Cool and short growing season is a limiting factor in walnut production.
Waterlogged and saline conditions of soil are also not favorable for walnut cultivation. Well drained silt loam soil having abundant organic matter is ideal. The soil should be free from rock and impervious clay. Coarse and sandy soil with hard pan, layers of gravel and fluctuating water table should not be chosen for walnut cultivation. Alkaline soils should be avoided for walnut planting.
3. Propagation, Rootstocks and Management Practices of Walnut:
Presently walnuts are mostly grafted on seedling rootstocks. But the resultant tree vigour, production and nut quality etc. are variable. Stock of Jugulans regia produces excellent graft union and is highly resistant to crown rot and black line disease, but is susceptible to crown gall, oak root fungus and salt accumulation in soil.
It is also somewhat resistant to root knot nematode. There is a need for testing other rootstocks for suitability. A number of other rootstocks viz. Northern California Black walnut (J. hindsii), Eastern Black walnut (J. nigra) and Paradox walnut (J. hindsii x J. regia) etc. are available and need thorough testing for their suitability under our conditions.
There is acute shortage of vegetatively propagated plants, which has forced walnut growers to plant seedlings of walnut with long gestation period. Nuts from current season’s crop need to be stratified in moist sand. After stratification, the nuts are sown keeping distance of 25 cm between nuts and 75 cm between row to row.
Seedlings of more than pencil thickness should be budded in July- August by patch budding or veneer grafting. The 5-6 months old scions should be used. They must be defoliated 10-15 days earlier. During spring, tongue/cleft grafting on one year old rootstocks with scions of similar diameters should be worked out. Temperature of 25°C±2°C at 75-80% RH is most suitable for scion take.
Recent researches at Central Institute for Temperate Horticulture, Srinagar have shown that wedge grafting with middle portion of scion, grafed in mid-March under polyhouse conditions has given very promising results and this method has been recommended for mass multiplication.
4. Planting and Spacing of Walnut:
December-January is most suitable for planting. Seedling plants are planted at 10 m x 10 m spacing, whereas spacing in budded or grafted plants is kept at 7 to 8 meters. Plants can be planted in square or in contour/terrace system if land is slopy. The seedling plants are to be planted @ 100/ha, whereas vegetatively propagated plants @ 200/ha in square system.
In case of hexagonal system the numbers of plants are 50% more. For organic cultivation also spacing of 10m x 10m for seedlings and 10m x 5m or 10m x 6m for grafts is appropriate, as slightly wide spacing helps in management and containing of pests.
5. Training and Pruning of Walnut:
Modified central leader system of training is preferred as it provides strong framework to the plants. No pruning is practiced as the plants of seedlings origin attain giant size and pruning is not possible. However in budded/grafted plants pruning needs to be done as per requirement of variety and situation.
Irrigation and Soil Moisture Conservation:
Although, walnuts are cultivated mainly under rainfed conditions, but they do require adequate soil moisture after 40-45 days of blooming. In the absence of sufficient soil moisture, plumpness of kernel and yields are reduced considerably. In such situations, when irrigation facilities do not exist, sod culture in combination with hay mulching in basins helps in moisture conservation.
6. Nutrient Management of Walnut:
Normally walnut is not cultivated in systematic manner and seedlings are planted on bunds or borders. Not many studies and reports are available on their nutrient removal and nutrient supplementation through organic sources or through cover crops/green manures etc. Therefore while deciding on organic nutrient management plan it is important to consider the recommendations in conventional systems.
In conventional system of cultivation in J&K state, fertilizer dose of 250 g nitrogen, 60 g of P2O5 and 250 g K2O is applied per fully grown plant per year. Full dose of P and K and half of nitrogen is applied 15 days before bloom and rest of nitrogen in two doses, first at 20 days after fruit set and second during early July.
Considering the nutrient release pattern by the manures and requirement of nutrients by plants at different stages, it is proposed to provide nutrient through two routes; one as soil application of FYM and manures and second through foliar feeding. Foliar feeding solution comprises of Vermiwash (5%) or Panchagavya (3%) or farm made protein hydrolysate (4-5 ml/lit of water). Any one or combination of two or all can be used depending upon the requirement.
7. Potential for Enhancing Total Production in Walnuts:
Out of all the walnut growing areas in J&K, Uttarakhand and HP, yields of walnut are quite high in districts of Anantnag, Pulwama and Baramulla.
Total production of walnut in J&K and also other areas can be enhanced by taking following steps:
1. For managing walnut plantation in an integrated and intensive manner, planting of walnut needs to be taken up in an organized manner using improved cultivars/local selections, grafted on dwarfing rootstocks. Solid blocks of 500 ha or 1000 ha each need to be planted.
2. Improved selections made by ICAR-CITH, Srinagr, J&K as ICAR-CITH series and other thin shelled cultivars like Vina, Serr, Franquette, Placentia, Eureka etc. need to be planted replacing old seedling plantations. Also old and unproductive plantations need to be top worked with thin shelled improved cultivars.
3. There is urgent need for adoption of improved cultivation practices providing life-saving irrigation and adopting mulching for conserving soil moisture at critical stage of nut development.
8. Harvesting of Walnuts:
Walnuts are usually harvested when hull colour changes from green to yellowish with cracks or when splitting starts at suture from pedicel end. In J&K, walnuts are harvested in September month, whereas in HP, harvesting starts in August and continuous up to September. In Uttarakhand walnut harvesting starts in October and continuous up to November.
After harvesting, nuts should be dehulled, washed and dried properly. Otherwise mould development can take place. The nuts are packed in gummy bags. After removal of shells, kernels are dried in shade and packed in appropriate boxes.
9. Varieties of Walnuts:
Most of the present plantations of walnut especially in J&K state are of seedling origin and have been grouped as:
i. Paper shelled
ii. Thin shelled
iii. Medium shelled
iv. Hard shelled
Because of recent interest in walnut cultivation in Himachal Pradesh and Uttarakhand states following varieties have been recommended:
Jammu and Kashmir – Lake English, Drainovsky and Opex Caulchry
Himachal Pradesh – Govind, Eureka, Wilson, Placentia, Franquette and Kashmir Budded
Uttarakhand – Black Moore, Hartail and Tutley-3.
More recently Central Institute of Temperate Horticulture, Srinagar has identified new walnut cultivars which have been named as ICAR-CITH Walnut -1 to ICAR-CITH Walnut -10. Out of these ICAR-CITH Walnut -5, ICAR-CITH- Walnut 8 and ICAR-CITH Walnut -10 seem to be very promising and need to be evaluated along with Pratap, Vina, Serr, Sunland, Franquette and Solding Selection in all the three states.