NutrientConcentrationBased on the leaf analysis, the nutrientconcentration of the cocoa plant is represented in the table 1 and table 2.Nitrogen concentration in both high and low yielding cocoa plants are similar,in high yielding population the mean value is 1.79 per cent and maximum andminimum values ranges from 2.4 – 0.95 per cent, where as in the low yieldingpopulation the mean concentration is 1.74 per cent and maximum and minimumnitrogen contents was observed to be 3.
16 to 0.86 per cent. Phosphorusconcentration in the high yielding population, the mean value is 0.21 per centand maximum of 1.0 per cent and minimum of 0.07 per cent similar values alsofound in the low yielding population.
In the case of Potassium concentrationranged from0.9 – 3.31 percent and the mean value is 1.98 per cent in the both the populations. In the case of thesecondary nutrients, in the high yielding population, Calcium concentrationranged from 0.83- 3.
9 per cent with mean value of 2.10 percent, but whereas the low yieldingpopulation recorded more Calcium concentration when compared to the highyielding ones ( 4.42 – 0.62 percent withmean value of 1.95 per cent).
In Magnesium, the concentration ranged from 0.55– 1.96 per cent and mean value of 1.11 percent which was slightly less than thelow yielding population. Sulphur concentration in the both high and lowyielding population are similar and the value range from 0.11- 0.37 per centwith mean value of 0.21 per cent.
Micronutrientconcentration was recorded in the ppm are represented in the table 1 and 2.Zinc concentration in the high yielding population range from 1. 023 – 0.
283ppm with an mean value of 0.586 ppm which is almost lower when compared to thelow yielding population. It was observed that the Copper concentration in thehigh yielding population ranged from 0.
075 – 0.798 ppm and mean concentrationof 0.152 ppm where as in the low yielding population the Copper concentrationranged from 0.623 – 0.
079 ppm with an mean value of 0.150 ppm.In the high yieldingpopulation the Iron concentration is ranged from 5.00 ppm to 0.25 ppm which isless compared to the low yielding population.
In the case of the Mangnesiumboth the high and low yielding population has the same concentration. CNDNorms Compositional nutrientnorms for the high yielding population have been represented in the table 3.The nitrogen (VN) norms was 3.69 with an standard deviation of 0.
24. phosphous norms (VP) is1.49 and 0.38 standard deviation. With regard to the potassium (VK)is 3.
18 and 0.25 (SD). Secondary nutrients like calcium, magnesium and sulphurthe Norms are VCa, VMg and VS are 3.80, 3.24and 1.
57 with standard deviation of 0.31, 0.21 and 0.26 respectively.
Compositional nutrientnorms for the micronutrient like Zinc, copper, iron and mangenisum arerepresented in the table 3. The norm for zinc (VZn) is -6.53 andstandard deviation of 0.34, VCu norms for copper is -8.00 and 0.32standard deviation.
In regard to the VFeand VMn the norms are – 5.81 and – 5.32 with standard deviation of0.29 and 0.42 respectively.PCAThe PCA conducted on logtransformed data result are represented in the table 6. For the both high andlow yielding population.
In the first PCA it is divided into two interactionsfor high yielding population N, P, K, Zn and Cu are positively correlated. Inthe second PC, Ca, Mg, S, Fe and Mn are positivity correlated with each others.In the low yielding population, N, P and K are positivity correlated on thefirst PC.
DiscussionSoils under cacao are often depleted and acidic because oflong-term cultivation with minimal fertilizer input, loss of nutrients througherosion and leaching, and removal by the harvested crops 3. This therefore implies that fertilizer usageshould be considered as a key factor in maximizing cocoa production; thepossibility of nutrition-related limitations to productivity has been raised inthe past but not examined in detail. Nutrientdemands of the cocoa trees will fluctuate throughout the year.
For instance,according to Santana and Cabala-Rosand (1982), N demand is greater during leaffall and shoot production. In April/May, young fruits are setting, while inSeptember, the developing pods have their greatest demand for nutrients(Wessel, 1971). Jadin and Snoeck (1985) suggest that further splits would leadto better uptake. For instance, Mg is best applied in November, at the end ofthe second rainy season in West Africa. 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. Variations in cocoa leafnutrient content do not necessarily indicate variations in the nutritionalstatus of the cocoa tree. A main problem with using cocoa leaf analysis is thatcocoa leaf nutrient content depends on many factors. These include leaf age,the development of new leaves, fruit bearing, light intensity, and seasonaleffects.
According to Hartemink and Donald (2005),nutrients in the annual litter fall represent 20–45% of the total N in thevegetation and 2–3% of the total N in the soil; 10–30% of the total P in thevegetation and 10–40% of the available P in the soil; and 15% of total K in thevegetation and 10–20% of exchangeable K in the soil. The speed at which thenutrients returned to the soil through litter fall become available for plantuptake depends on decomposition rates. Calculated decomposition ratecoefficients (k-values) in cocoa litter vary. Dawoe et al. (2010) foundk-values of 0.221–0.224 per year in Ghana, while Fontes et al. (2014) foundrates of 0.
51–1.11 per year inThe nitrogen concentration of both the high yielding and lowyielding cocoa plants were almostsimilar and this shows that nitrogen isnot the limiting factor in most of the cocoa plantations of the region .Since the farmers greatly resort to additionof organic manure in the fields (Sujathaet al., 2012).
Phosphorus, potassium,calcium and magnesium levels of the low yielding plants were lower the highyielding population this shows that the application of phosphorus, potassium,calcium and magnesium will certainly bring about a yield increase in the lowyielding plantation. This also supports the result that the cocoa harvestinginvolves the removal of pod husks from the field; the amount of potassiumremoved increased more than five folds. Low yielding plantations also showedlesser concentrations of Fe and other micronutrients show similar trends inboth the population. The nutrient imbalancesin might have resulted in poor yield in the plantations, Similar resultswere obtained by Bhat et al ., 2013. In correlation matrix in the both high and low yielding populationas the results are discussed above, this interaction may be due to the overusage of organic manure. It was reportedthat the soil OM exerts a significant and direct impact on the availability ofZn, Fe, and Mn but has little influence on the availability of soil Cu (Zhang, Wang, and Jin 2001).
Application ofappropriate rates of N, P, and K fertilizers can increase soil Cu, Zn, and Mnavailability (Zhang, Guo, and Nan 2004).Shortage of K also increases Cu, Zn, Fe, and Mn concentrations (Cheng,1995).