Nitrogen, Phosphorus, and Potassium are essential for healthy coconut palm growth, nut setting, and high-quality copra production. Nitrogen enhances vegetative growth and leaf color, phosphorus supports strong roots and flowering, while potassium improves drought resistance and nut quality. Deficiencies in any of these can cause stunted growth, poor yield, and vulnerability to pests. Proper nutrient management, including timely fertilizer application and organic amendments, is crucial to ensure sustained productivity. By understanding the role of each nutrient and recognizing deficiency symptoms early, farmers can maintain robust, high-yielding coconut palms and improve farm profitability in the long term.
(i) Nitrogen
Nitrogen is essential for coconut development, enhancing leaf color, vegetative growth, and dry matter quality. It is necessary for enzymatic functions in coconut palms, impacting spathe emergence and nut setting. Nitrogen deficiency results in yellowing leaves, reduced size, and stunted growth due to impaired cell division, also affecting leaf protein content and flowering. Annual nitrogen application of 560 grams per palm is advised, with urea being a common nitrogen source. Urea, containing 46% nitrogen, requires conversion to ammonium and nitrate for plant availability. However, about 40% of nitrogen from urea is lost through leaching and volatilization, especially in coarse soils, necessitating frequent applications. Continuous urea usage may cause soil acidification from ammonium conversion to nitrate. Ammonium sulphate, containing 20.6% nitrogen, also risks higher salt index and acidification. Mono Ammonium Phosphate (MAP), with 11% nitrogen, is favored for fertigation due to its nutrient composition, while Di Ammonium Phosphate (DAP) provides controlled nitrogen release with 18% nitrogen and 46% P2O5.To reduce nitrogen loss, slow-release fertilizers like neem-coated, sulfur-coated, and lac-coated urea are recommended, alongside nitrification inhibitors such as N-Serve. Applying neem cake at 3 kg per palm annually further minimizes nitrification losses.
Nitrogen deficiency arises from insufficient soil nitrogen, initially manifesting as uniform chlorosis in older leaves, progressing to younger leaves. Severe deficiency halts growth and induces leaf drop, with symptoms aiding diagnosis, although leaf analysis offers confirmation. Distinction from iron or sulfur deficiency is crucial, as their chlorosis affects younger leaves most severely. To remedy nitrogen deficiency, foliar application of 2% urea three times biweekly, soil application of 1-2 kg urea per tree, or root feeding of 1% urea at specified intervals is suggested.
Yellowing of leaves in lower leaf whorl
(ii) Phosphorus
Phosphorus is vital for energy processes in plants and is integral to RNA and DNA. It is critical for root growth, flowering, and enhancing copra yield in coconut palms. Phosphorus is immobile in soil but mobile in plants. A phosphorus deficiency results in delayed maturation and inferior copra quality. This issue is prevalent in calcareous soils due to phosphorus fixation as calcium phosphate. To maintain sufficient phosphorus, an annual dosage of 320 grams of P2O5 per palm is advised. Single Super Phosphate (SSP), containing 16% P2O5, is the predominant phosphatic fertilizer, while Di Ammonium Phosphate (DAP) offers 46% P2O5. The addition of phosphorus-enriched farmyard manure (FYM) can mitigate phosphorus fixation and enhance its efficacy in coconut cultivation. Phosphorus deficiency may manifest as: - Leaf purpling, with severe cases leading to yellowing and premature drying. - Reduced growth vigor. - Upright leaf position. - Early leaf drop. - Diminished growth, smaller leaves, and fewer foliage. - Limited root expansion. Nonetheless, phosphorus deficiency lacks distinct visual symptoms apart from stunted growth and diminished yield. To remedy phosphorus deficiency, it is advised to foliar spray 2% DAP biweekly and apply 5 kg of FYM per tree. Additionally, root feeding with 1% DAP at 2 ml biannually may also prove advantageous.
(iii) Potassium
Symptoms of potassium deficiency first appear on the oldest leaves, gradually spreading to younger ones, and manifesting as translucent yellow or orange spots on leaflets, with yellowing along the leaf margins. Older leaves may exhibit necrotic spots, curling of leaflet tips, and necrotic areas along the margins, which eventually wither. Affected trees often appear yellow and stunted, with slender trunks and short leaves. Visual symptoms can often diagnose this disorder, though leaf nutrient analysis can help differentiate late-stage potassium (K) deficiency from manganese (Mn) deficiency, which presents similar symptoms but with distinct spotting patterns. Regular application of potassium fertilizers is crucial for prevention and treatment, particularly on sandy soils where controlled-release potassium sources are more effective than water-soluble ones. Recommended treatments include applying resin-coated K₂SO₄ at 3-4 kg per tree, four times a year, along with 2 kg of MgSO₄ per tree, and root feeding with 200 ml of 1% KCl three times a year. While potassium does not form vital compounds in plants, it plays a critical role in enzyme activation, water regulation, drought tolerance, and enhancing resistance to pests and diseases. It is also important for improving copra quality, with common deficiency symptoms including chlorosis, marginal scorching, necrosis, small resinous leaf spots, and increased susceptibility to pests and diseases. An annual application of 1200 g of K₂O per palm is recommended, using either sulphate of potash (white potash) or muriate of potash (red potash) as fertilizers.
Marginal scorching and Necrotic spots
