Plant analysis gives a direct indication of thenutritional status of the plant and may show a strong correlation with yields(Ahn, 1993; Foster and Prabowo, 2002). Plant chemical analysis may be anotherhelpful tool in establishing fertilizer requirements. The plant’s nutritionalstatus is the net effect of variables related to soil, plant, climate, andmanagement (Ahn, 1993). In perennials, nutrient deficiencies can bedetected through plant (Usually leaves are used) in the analysis and correctedbefore they have an effect on production (Ahn, 1993; Smilde, 1985). Foliardiagnosis will provide a better understanding on the nutrient uptake and theit’s proper interpretation will help in providing idea about the plant nutrientstatus.
Cocoa(Theobroma cacao L.) is apreferentially alogamous tropical woody species formerly in the Sterculiaceaefamily (Cuatrecasas, 1964) and reclassified in the Malvaceae family (Alverson et al., 1999) which originates from thetropical rainforests of the Americas. Cocoa is grown almost exclusively within10°N and 10°S of the equator; predominantly grown in the tropical areas ofcentral and south America, Asia and Africa (Marita et al., 2001). Here, theclimate is warm and humid and thus suitable for growing cocoa (Hartemink andDonald, 2005). It is considered one of the most importantperennial crop in the planet, Global annual production of cocoa currentlyexceeds 4 million tons. However, while global demand for sustainable cocoa isgrowing annually by 2 to 3 %, while Africa still contributes about 72% of the globalsupply (ICCO, 2015).
Cocoa is a major source of export earnings for manyproducing countries; mostly it is commercially exploited for seed output mainlyfor chocolate manufacturing and consumed in Western Europe and the UnitedStates (ICCO, 2012, 2015). However, derivatives and by products of cocoa canalso be transformed in cosmetics, fine beverages, jellies, ice creams. Around80–90% of global cocoa production occurs on smallholder farms, by about 5–6million cocoa farmers worldwide (WCF, 2014). Estimated at Ghana is around 400kg/ha (Aneani and Ofori-Frimpong, 2013) while potential yields modeled at 5000kg/ha under rainfed conditions (Zuidema et al., 2005) Ascocoa is a perennial, the duration of its productive life should also be takeninto consideration when assessing productivity. Trees come into bearing after2–6 years depending on the variety and location (Wessel, 1971; Wood and Lass,1985).
Toachieve high productivity, cocoa requires a soil abundant in nutrients (Wessel,1971). The importance of several other soil characteristics, such as pH andorganic matter, is largely due to their influence on the availability ofnutrients. Althoughnutrients have different functions in the development of the tree (e.g., canopyformation, flowering, pod production), all nutrient deficiencies willultimately lead to decreased yields. It is hypothesized that pod production isfundamentally determined by the available nutrients in the tree at differentstages from flower initiation to pod maturity (Hutcheon, 1976).
Soil nutrientlevels have declined and can no longer support productive cocoa (Appiah et al.,2000). Criticalvalues for leaf nutrient analysis are referred to for cocoa (Table 14).Variations in cocoa leaf nutrient content do notnecessarily indicate variations in the nutritional status of the cocoa tree. Amain problem with using cocoa leaf analysis is that cocoa leaf nutrient contentdepends on many factors. These include leaf age, the development of new leaves,fruit bearing, light intensity, and seasonal effects.
Soil nutrients in cocoa plantation are being mined annually viacocoa harvest (Ogunlade et al.,2009). Opeyemi et al, (2005) reported that an effective useof fertilizer on cocoa would help not only to improve yield but also has theadvantages of profitability, product quality and environmental protection. Soils under cacao are oftendepleted and acidic because of long-term cultivation with minimal fertilizerinput, loss of nutrients through erosion and leaching, and removal by theharvested crops 3. This therefore implies thatfertilizer usage should be considered as a key factor in maximizing cocoaproduction; the possibility of nutrition-related limitations to productivityhas been raised in the past but not examined in detail.
In India, Cocoa was introduced inthe early part of 20th century and now it has become one of theimportant horticulture crops and where it is largely confined to southernstates, viz., Kerala, Karnataka, Tamil Nadu and Andhra Pradesh. The total areaunder this crop is 46,318 ha with a production of 12,954 MT (DCCD, 2011). Interms of production, India ranks nineteenth in the world.
Large area of cocoa cultivation is underirrigated coconut and the progressive growers who opt for mixed cropping,better market opportunities have made cocoa as an undisputable intercrop in thestate. However, the productivity is low which is only 2 kg dry beans tree-1 asagainst the potential yield of upto 4 kg tree-1 through improved productiontechniques. As thedemand for cocoa in India is more (30,000 MT) than the present supply (12,954MT), cocoa production needs to be intensified (DCCD, 2011). Cocoa productionenvisages techniques to improve yield through drip and fertigation, nutritionalmanagement. Nelliat (1984) concluded that cocoa was a heavy feeder ofpotassium. A good crop of cocoa removes as much as 170 kg of K ha-1.Potassium is also the principal element present in the pods of cocoa(Fassbender et al.
, 1985). Omotoso(1975) reported that a crop of 1000kg dry Cocoa beans removed about 20kg N, 41kg P and 10kg K and where the method ofharvesting (as in Nigeria) involves theremoval of pod husks from the field, the amount of potassium removed increasedmore than five folds. Wessel (1971)reported that there is a steady decline in almost all the nutrients with lengthof cultivation of cocoa. Ogunlade and Aikokpodion (2006) reported thatphosphorus is grossly inadequate for optimum cocoa yield in cocoa ecologies ofNigeria.
Nutrient demands of the cocoa trees will fluctuatethroughout the year. For instance, according to Santana and Cabala-Rosand(1982), N demand is greater during leaf fall and shoot production. InApril/May, young fruits are setting, while in September, the developing podshave their greatest demand for nutrients (Wessel, 1971).
Jadin and Snoeck(1985) suggest that further splits would lead to better uptake. For instance,Mg is best applied in November, at the end of the second rainy season in WestAfrica. However, they acknowledge that many different times of fertilizerapplication are not economically feasible.
They advise three application timesduring the West Africa. However, they acknowledge that many different times offertilizer application are not economically feasible. They advise threeapplication times during the year. According to Jadin and Snoeck, 1985, Pshould be applied before flowering, half of K and all Ca and Mg duringflowering, and the other half of K 2–3 months later.Plant analysis has been considered a very practical approach fordiagnosing disorders and formulation fertilizer recommendations (Kelling et al. 2000).
Plant analysis, inconjunction with soil testing, becomes a highly useful tool not only indiagnosing the nutritional status but also an aid in management decisions forimproving the crop nutrition. Approaches to diagnosingleaf nutrient status can be estimated by Compositional Nutrient Diagnosis (CND)(Parent and Dafir, 1992;). For CND, the high-yield subpopulation is selectedfrom a crop survey database.
This technique has been effectively utilized forthe establishment of nutrient norm and for identification of yield limitingnutrients in fruit crops like banana (Raghupathiet al, 2002,). With the background, present study was conductedwith the following objectives, To study the present status of nutrients incocoa growing enterprises of Puttur region of Karanataka and To develop CNDnorms for identification of common yield limiting nutrients.