Fertilizer Requirements « Applied Agricultural Resources. Introduction. In modern cocoa cultivation, the aim is to maximize early growth and obtain high early yields and sustained peak yields subsequently. To achieve this, it is necessary to have a good understanding of the factors affecting growth and yield of cocoa and to put in the necessary management practices on time as required by the cocoa plant. An essential ingredient in most cocoa growing situations is high fertilizer input. However, the agronomy of cocoa is much more complex than with other crops eg. To achieve high yields therefore, these factors should not be limiting. In this paper, the technique for drawing up fertilizer recommendations for the crop is outlined and the interrelationship of the agronomic factors in cocoa plantations with nutrition is discussed. It is hoped that this will enable managers to understand the need for ensuring that planting practices are correct in order to obtain the maximum yield responses from fertilizer applications made. Nutrient requirement of cocoa. The cocoa plant in its native habitat on the ground storey of the Amazon jungle is very heavily shaded and grows slowly with very low yields. Under these circumstances, nutrient requirements are probably very low. Nutrients are taken up by cocoa in growth and for yield.
The nutrients may be immobilized in the plant or recycled as leaf litter when the plant are mature and the nutrients are exported in the pods that are removed from the field. The growth and yield potential of cocoa is primarily determined by management factors, soil, climate and the availability of nutrients for growth and yield. The former factors determine the potentials largely and to assess nutrient requirements accurately, a good assessment of the potential growth and yield under the prevailing soil and climate conditions and expected management inputs is necessary. The most important management factors are probably the types of planting materials affecting the yield potential and growth and nutrient uptake characteristics, nursery practices affecting the quality of seedlings, early growth and yields, shade regimes which interact very strongly with most other factors and determine the growth and yield that will be obtained, weed control practices determining the extent of competition for nutrients and soil moisture, plant density determining the overall yield and nutrients immobilized as well as pests and diseases which affect the total dry matter production and growth rates and thereby nutrient requirements. The shade regime and the types of shade trees used are important as growth rates will be affected markedly. The extent of competition by the shade tree could be very significant e. Gliricidia. The main climatic factors affecting nutrient requirements are probably the rainfall affecting soil moisture, temperatures affecting overall growth and also degree of moisture stress and light available determining the energy available to the plant for dry matter production and also having a bearing on the soil moisture requirement by the plants. The third important factor is the soil. Although individual soil properties are measured and determined, they are finally intergrated to determine its ability to supply and store moisture and nutrients for the plant and its properties as a medium of growth for the roots and root activity which determine in turn its ability to exploit the soil moisture and nutrient contained therein. These factors discussed so far determine the growth and yield potentials for cocoa in an area. An estimate is now required of the nutrients required by the cocoa plant for their growth and yield. Several estimates have been made of the nutrient requirements of cocoa e. Thong and Ng (1. 97. Teo and Chew (1. 98. These estimates obtained depend on the growth and yield expected under the growth conditions prevailing. It is necessary however to make these estimates to try and quatify the amounts of nutrients that are required and the important nutrients taken up by the plant. For the purpose of this paper, the data provided by Thong and Ng (1. Table 8 shows dry matter production and distribution in cocoa plants of different ages. And climatic conditions for the main three cocoa growing. Calculation of the fertilizer requirements Soil analytical data from the Soil Research Institute. Para el cacao (Theobroma cacao L.). climatic conditions to cocoa requirements. ISSN print: 0258-5936. range provided adequate soil moisture throughout. CACAO ROADMAP Republic of the. Agro Climatic Requirements of Cacao. Soil Requirement Best soil is made-up of aggregated clay or loamy sand with 50% sand, 30-. Dry matter accumulation in cocoa increases very rapidly up to the fifth year after planting and stabilizes after that. The nutrients immobilized in the plant are shown in Figure 4 where the early very rapid growth rate is reflected in the very rapid nutrient uptake especially of potassium and nitrogen in the first 5 years. Table 8 : Dry matter production and distribution in cocoa plants. Age of plants (months)Total dry matter (kg/plant)% Distribution. Leaves. Stem. Branches. Fruits. Roots. 50. Thong and Ng, 1. 97. Figure 4 : Nutrient uptake of cocoa (Ling, 1. The total nutrients immobilized in 5 year old cocoa in 2 inland soils in Malaysia when the cocoa canopies have reached the plateau in growth rate are given in Table 9. The very high accumulation in the cocoa plants of potassium and nitrogen is clearly seen. Taking the mean values of 2. N and 3. 00 kg/ha K, this is equivalent to 1. These nutrients are locked up within the bushes and only become available again to the plant through recycling of the leaf litter and from leaching particularly of K from the leaves in rainfall. Cocoa leaf litter production and nutrient contents is shown in Table 1. Very high amounts of nutrients are recycled in the leaf litter particularly for N, K, Mg, Ca and after the sixth year. Nutrient cycling is still not high in the fourth year. Beside nutrients removed from the soil and immobilized in the bushes, nutrients are exported as yield is removed in the pods harvested. The pods have very high nutrient contents equivalent to 3. N, 5. 4 kg K, 4. 9 kg P, 5. Mg and 4. 9 kg Ca at a yield level of 1 ton dry beans/ha/year (Table 1. The beans are particularly high in N and P and the pods in K contents. The nutrients removed vary with age and yield levels. If the husks are recycled, considerable quantities of nutrients especially K and N, are returned and they have a marked effect on the nutrient availability of the soil as seen in Table 1. Nutrient requirements may then be markedly reduced. In the monocropping system therefore, the cocoa bushes have very high nutrient requirement for growth and yield, increasing very rapidly in the first 5 years and then reaching a plateau after that with subsequent increases depending mainly on export of nutrients in increased yield. Even then, the nutrient requirements are reduced if husks of the pods which form a very substantial portion of the nutrients removed are recycled to the fields. In addition, in mature areas, nutrient recycling in the litter is significant. Overall nutrient requirements in mature cocoa may therefore not be high. The above discussion deals with the basic factors involved in estimating nutrient requirements in cocoa. However, as the variables cannot always be assessed accurately, it is useful to employ additional checks to determine if nutrition of the cocoa trees is good. Commonly, the techniques adopted are to check for nutrient deficiency symptoms (Loue, 1. Nutrient deficiency symptoms are described and illustrated in Wood (1. Tables 1. 3 and 1. Table 9 : Nutrients immobilized in 5 year old cocoa (Ling, 1. Nutrientkg/ha. Munchong. Bungor. N2. 56. 24. P2. 72. 2K3. 54. 27. Mg. 81. 87. Ca. 19. Dry matter. 27,7. Table 1. 0 : Cocoa litter production and nutrient contents (Ling, 1. Age (years)Dry matter (kg/ha)kg/ha. NPKMg. Ca. 42. 53. Table 1. 1 : Nutrients in pod production (Ling, 1. Ages(years)Dry bean yield(kg/ha)Component(kg)NPKMg. Ca. 34. 50. Beans. Husk. 4. 9. 0. 6. Total. 14. 1. 2. 2. Beans. 20. 4. 3. 6. Husk. 10. 6. 1. 3. Total. 31. 0. 4. 9. Beans. 28. 6. 5. 0. Husk. 15. 4. 2. 0. Total. 44. 0. 7. 0. Table 1. 2 : Effects of pod husks on soil chemical properties (0- 1. Ling, 1. 98. 3 )Parameter. Treatment. Without pod husks. Pod husks (1. 0 kg dry/tree)PH4. Total N (%)0. 1. 39. Avail. P (ppm)5. 86. Org. C (%)1. 1. 31. Acid Ext. K (meg/1. Acid Ext. Mg. 0. 9. Acid Ext. Ca. 1. 1. Table 1. 3 : Classification of major leaf nutrient levels in cocoa(Modified after Murray, 1. Nutrient% on D. M. Deficient. Low. Normal. N< 1. 8. 01. 8 – 2. P< 0. 1. 3 – 1. K< 1. 2. 0 – 1. Ca< 0. 3. 00. 3. Mg< 0. 2. 00. 2. Table 1. 4 : Classification of major leaf nutrient levels in cocoa(Southern and Dicks, 1. Nutrientppm on D. M. Critical level. Deficient level. Mn. Fe. 50. 30. Zn. 30. Cu. 64. B2. 51. 5Nutrient deficiencies may be indicated from the analysis results especially in gross deficiencies. However non- nutritional factors eg. Interpretation of leaf analysis in cocoa is not as advanced as in other crops due to difficulties in correlating leaf nutrient levels with yields, probably a result of the high number of variables which affect leaf nutrient levels in the crop. After consideration of the above factors, in particular, the growth and yield potential of the cocoa, the amount of nutrients required for the expected growth and yield and the nutrient supplying powers of the soil, it is possible to estimate the nutrients required by the cocoa to attain the growth and yield aimed for and to formulate fertilizer recommendations. Fertiliser recommendations for cocoa. To draw up the fertilizer recommendations for cocoa, the choice of fertilizers to be used, methods and areas of fertilizer applications and factors affecting efficiency of fertilizers used have to be considered. There is usually a wide choice of fertilizers available. It is necessary particularly to consider the availability and expected efficiency of uptake of the nutrients in the fertilizers, any possible effects on the soil and finally the cost/unit nutrient uptake which is expected. An example may be urea which is the cheapest N fertilizer. However, volatilization losses of N from this fertilizer may be 3. N blow- off may be very nearly complete so that no response is obtained from the fertilizer (HRU unpublished report).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
November 2017
Categories |