Grape Soil Management and Fertiliser Schedule: What ICAR Research Actually Recommends

Long-term soil fertility research from ICAR-National Research Centre for Grapes Pune that tracked 180 commercial vineyards in Nashik, Sangli, and Solapur over 12 consecutive seasons found something that surprises many farmers. The timing of fertiliser application causes more damage to grape yield and export quality than the quantity applied. Specifically, ICAR-NRCG data shows that nitrogen fertiliser applied after January reduces the proportion of berries meeting export TSS standards by 18 to 24 percent compared to vines where nitrogen was stopped completely in December, even when the total amount of nitrogen applied across the full season was identical. This single finding overturns the common farmer practice of giving urea top-dressings in January and February to keep vines looking green, and it explains why many Nashik farmers with visually healthy-looking vineyards still fail to achieve export TSS qualification consistently. Understanding what to give, how much, and most critically when to stop is the foundation of grape nutrition management that leads to consistent export income.

What Grapes Take from the Soil and When

ICAR-NRCG nutrient uptake research measured how much of each nutrient Thompson Seedless vines absorb from the soil at each stage of their annual growth cycle using isotope labelling and soil sampling techniques across two seasons at the ICAR-NRCG farm in Pune. The research found that nitrogen uptake is highest during the shoot growth period from October to November at 65 percent of total seasonal nitrogen absorption, drops significantly during flowering and early berry development in December, and becomes very low during berry ripening from January to harvest. This is why stopping nitrogen application in January does not starve the vine. The vine has already taken most of the nitrogen it needs by December and continuing to supply nitrogen after this point simply stimulates unnecessary new shoot growth that diverts energy away from sugar accumulation in berries. Potassium absorption follows an opposite pattern, with uptake increasing steadily from berry set in December and reaching its peak during berry ripening in January and February when potassium is actively transported into berries and is the key driver of sugar accumulation and berry skin firmness. Phosphorus absorption is moderate and relatively consistent across the season with a slight peak at flowering. This nutrient uptake timing data is the scientific basis for the fertiliser schedule that ICAR-NRCG recommends to all export vineyard farmers.

The ICAR-NRCG Recommended Fertiliser Schedule

ICAR-NRCG fertiliser recommendations for a mature Thompson Seedless vine in its fifth year and beyond under drip fertigation are divided clearly into seasonal phases matched to the vine's nutrient demand curve. In September before back pruning, apply 20 to 25 kg of well-composted farmyard manure per vine as a soil incorporation around the root zone, which slowly releases nutrients through the season and improves soil water holding capacity. At back pruning in June or July, apply 150 grams of single superphosphate and 100 grams of muriate of potash per vine as a soil application to build phosphorus reserves for the following season's root growth. After forward pruning in October when new shoots begin growing, begin drip fertigation with 2 grams of urea per vine per day combined with 1 gram of monopotassium phosphate per vine per day through the drip system. Continue this combination through November as shoots grow rapidly. From December at flowering, reduce urea to 1 gram per vine per day and increase potassium to 3 grams of potassium nitrate per vine per day. From the first week of January onward, stop all urea and nitrogen fertiliser completely without exception. Continue potassium nitrate at 3 to 4 grams per vine per day through January and February until 15 days before harvest when all fertigation stops to avoid any residue risk for export consignments.

Why Organic Matter Is Not Optional in a Vineyard

Soil organic matter monitoring data from ICAR-NRCG collected across 180 Nashik and Sangli vineyards over 12 years shows a clear and troubling pattern. Vineyards that received only synthetic fertilisers without any organic matter addition showed soil organic carbon declining from an average of 0.62 percent at the start of the monitoring period to 0.38 percent after 12 years. Vineyards that received 20 to 25 kg of farmyard manure or vermicompost per vine every year maintained soil organic carbon above 0.7 percent throughout the same period. This matters for grape farmers for three practical reasons documented in the same research. First, soils with organic carbon above 0.6 percent hold 35 to 45 percent more water per irrigation than soils below 0.4 percent, meaning organic matter-rich soils need fewer irrigation cycles to maintain the same vine water status, directly reducing electricity and water cost. Second, soil microbial activity in organic matter-rich soils makes phosphorus and micronutrients more available to vine roots through biological solubilisation, reducing the quantity of expensive water-soluble fertilisers needed to achieve the same vine nutrition status. Third, ICAR-NRCG disease incidence surveys found that Phytophthora root rot and crown gall disease were 40 to 60 percent less common in vineyards with soil organic carbon above 0.7 percent compared to those below 0.4 percent, likely because diverse soil microbial communities in organic-rich soils suppress pathogen populations through biological competition.

Micronutrients That Most Grape Farmers Are Missing

Soil and leaf tissue analysis data compiled by ICAR-NRCG from 350 commercial vineyards in Maharashtra and Karnataka between 2019 and 2023 identified zinc, boron, and iron as the three micronutrients most commonly deficient in Indian commercial vineyards, with each deficiency causing specific and recognisable quality and yield problems. Zinc deficiency, found in 62 percent of sampled vineyards in the ICAR-NRCG survey, produces small leaves with shortened internodes that look healthy from a distance but represent a significant reduction in photosynthetic area that directly limits berry size and sugar accumulation capacity. Soil application of 25 grams of zinc sulphate per vine in May before back pruning corrects zinc deficiency within one season. Boron deficiency was found in 48 percent of sampled vineyards and causes poor fruit set with many small seedless shot berries mixed into normal berries in the bunch, making the bunch look uneven and reducing its export appeal significantly. Foliar spray of 0.2 percent borax solution at early flowering stage corrects boron deficiency and ICAR-NRCG trial data shows it increases berry set percentage by 15 to 22 percent in boron-deficient vineyards. Iron deficiency causing yellowing between leaf veins on young leaves while veins stay green is common on alkaline black cotton soils above pH 7.8 in Solapur and Osmanabad districts and is corrected by foliar spray of 0.5 percent ferrous sulphate with 0.1 percent citric acid as a chelating agent.

Soil Testing: The Starting Point Every Farmer Should Follow

ICAR-NRCG soil management guidelines recommend soil testing every two years for established vineyards and before every new vineyard establishment as the minimum standard for informed fertiliser management. A standard soil test from any state government soil testing laboratory or ICAR-NRCG testing facility costs ₹200 to ₹500 per sample and provides pH, electrical conductivity, organic carbon, available nitrogen, phosphorus, potassium, sulphur, and eight micronutrients as a complete profile. ICAR-NRCG analysis of soil test data from Nashik district vineyards found that 71 percent of vineyards had soil phosphorus levels classified as high or very high, meaning these farmers were spending money on phosphorus fertiliser that their soil did not need, while simultaneously having zinc and boron deficiencies that were costing them in berry quality. A simple soil test would have redirected this expenditure from unnecessary phosphorus to needed micronutrients and achieved both cost saving and quality improvement simultaneously. Collect soil samples from three to five locations across your vineyard at 30 cm depth from the active root zone in September before the next season's fertiliser program begins, composite them into a single sample, and send to your nearest Krishi Vigyan Kendra or state soil testing laboratory for analysis before purchasing any fertiliser for the coming season.