Coffee being a perennial crop, the plant has the dual function of maturing the crop and producing fresh cropping wood frame work for the succeeding year simultaneously. In coffee cultivation, nitrogen, phosphorus and potassium are considered as major nutrients; calcium, magnesium and sulphur as secondary nutrients, while iron, manganese, copper, zinc, molybdenum, boron, sodium and chlorine as micro-nutrients. All the essential nutrient elements supplied in adequate quantities to sustain the growth and yield of the plant is called balanced fertilization. Restrictions on coffee production due to soil nutrient deficiencies are removed by applying appropriate fertilizer in right time and adequate quantities. The most economic quantities of nitrogen, phosphorus and potassium required to be supplied to a given block depends on the estimated yield, performance of plants for the last three to five season and the soil test data. Dose of nutrients applied without considering the soil test values will be inaccurate, uneconomic and incomplete.
Nutrient Requirement for Coffee
It has been estimated that a tome of clean coffee removes approximately, 40 kg N, 7 kg P2 O5 and 45 kg K2O in the case of Robusta respectively from the soil. The nutrient requirement of biomass to produce one tonne of clean coffee (approximately 6000 kg fruits of Arabica of 5000 fruits of Robusta) is roughly 13 kg N, 2.3 kg P2O5 and 15 kg K2O respectively. Taking into consideration the crop removal of nutrients, nutrient loss through leaching, fixation and fertilizer use efficiency (FUE), dosage of nutrients required to realize targeted yield are furnished in the table.
For mature Arabica as well as Robusta coffee, where coffee yields are not exceeding 1 t per unit area(one ac or ha), a mandatory/sustenance dose of 20:20:20 kg of N:P2O5:K2O per year has to be given while, for the area where the production levels are exceeding 1 t up to 1.5 t mandatory/sustenance dose has to be revised to 30:30:30 kg. The mandatory/sustenance dose of fertilizers takes care of biomass (bush frame work) nutrient requirement coffee plants. In addition to the mandatory/substance dose, for every 100 kg of clean coffee production, application of 10:7:10kg of N:P2O5:K2O is essential. These general recommendations are subject to modification for individual estates based on soil analysis report. Annual fertilizer doses suggested for young coffee based on age and different appendix 8. These annual doses are in a year and for nutrient sources other than those mentioned, the quantities need to be calculated according to nutrient content of those fertilizers. Nitrogen and potassium requirement of coffee plants grown without shade trees are generally higher than the plants grown under normal shade. Similarly coffee under irrigated conditions requires more nutrients as these plants tend to produce higher crops. The annual dose of nutrients required to be applied will have to be worked out strictly.
Sulphur, though recognized as a secondary nutrient for plants, studies have revealed that its requirement for coffee is as much as much as phosphorus and it is being considered as a major nutrient along with N, P and k. soil survey on sulphur status in coffee plantations revealed that soils are tending to be increasingly deficient in available sulphur. The increased occurrence of sulphur deficiency can be attributed primarily to two reasons. They are:
- Increased use of high analysis fertilizer containing little or no sulphur.
- Subsistence agriculture being transformed to intensive one through the of fertilizers and intensive cropping
- Patterns resulting in the creation of a large gap between the sulphur supply and requirements in soil-crop cycle.
Therefore, soil and crop requirement of sulphur has to be taken care of. It has been found that sulphur is not only an essential nutrient for optimum yield of coffee but also essential to maintain and improve the quality. Every metric tonne of clean Arabica coffee produced needs roughly about 15 to 20 kg of sulphur while Robusta needs 20 to 25 kg. therefore, depending on the yield and nutrient status of the soil, sulphur dosage needs to be adjusted and supplied along with N,P and K during post monsoon period in a single dose. sulphur can be applied in the form of ammonium sulphate, calcium or magnesium sulphate, elemental sulphur , potassium sulphate or single super phosphate preferably during the post monsoon period.
Time and Frequency of Fertilizer Application
The time and frequency of fertilizer application have considerable influence on growth and yield. Efficient and effective use of fertilizers implies timely application when they are most needed by the plant. Studies have indicated that the peak periods of demand for nutrients are at the time of flowering. Fruit set and development and maturation of the crop. Hence fertilizer application is suggested during blossom (February-March), pre-monsoon (May-June), break in monsoon (August) and post monsoon periods (September-October) in areas under South-West monsoon.
It is advisable to apply the total annual dose of fertilizers in a minimum of 2 or more number of splits as it reduces the losses of nutrients through leaching, fixation, improves FUE and ensures the supply of nutrients to the plants throughout the year. Application of large amounts of fertilizers at a single stretch on an excessively moist soil when temperature (sun shine) is very high should be avoided as far as possible. When the annual dose to be applied per acre is small, then the practice of two rounds of application may be followed to be applied per annum is very high and the same may be split in 3 or 4 round of application, the fertilizer dose should be restricted to a maximum of 40:30:40 kg of N: P2O5:K2O per acre.
Application of calcium sulphate or magnesium sulphate at the rate of 25 to 30 kg ac-1 during post-monsoon period should be encouraged in order to improve soil sulphur status as well as soil condition. However, continuous aapplication of magnesium sulphate should be avoided in order to restrict the possible imbalance in potassium uptake by accumulated magnesium ions.
Changes of adulteration are more in readymade fertilizer mixtures, rock phosphates, super phosphate, liming materials and organic manures. It is desirable to get these materials analysed in the laboratories of the Coffee Board’s Research Department before they are used In the field.
One month gap should be given between fertilizer applications and liming during the year of liming materials reacts with phosphatic fertilizers making them less soluble. One should ensure sufficient soil moisture before application of fertilizer/manures. Better fertilizer use efficiency can be obtained in coffee fields by the application iof farm yard manure/compost or any other organic manure at least once in 2 to 3 years at the rate of 2 to 3 t ac-1. Soil testing should be routinely done at least once in 2 to 3 years for efficient management of nutrients.
Method of Fertilizer Application
A simple but sufficient effective method of fertilizer application is suggested for coffee plantation is suggested for coffee plantations with a slight modification to the existing method of ‘drip circle application’. Sweep the mulch beneath the coffee plants towards the base and disturb the soil one foot away from the stem slightly using stick or forks. Apply fertilizer uniformly and evenly in a broad circular band in this area, rework the soil and cover again with the mulch. This methods is very efficient as it avoids vocalization and washing away of nutrients. In steep area fertilizers can be applied in semi arch (horse shoe) from on the upper side of the stem down the slope.
Mixing of Fertilizers to get the Required Nutrients Ratios
Mixing different N,P,K sources in definite quantities to get the required N:P2O5:K2O are present in appendices 7 and 9 respectively. While mixing the fertilizers for soil application their compatibility has incompatible nutrient source may either lead to caking up and handling of the mixture may be difficult or the fertilizer mixture may fail to supply the required nutrients to the plants as the incompatible fertilizers may chemically react with each other and convert the essential nutrients to unavailable form. Thus the nutrient management program may not achieve its goal in spite of applying fertilizers when incompatible nutrient sources are used. A chart depicting the compatibility of fertilizers is presented below.
Micro Nutrients Management in Coffee Cultivation
Iron, manganese, copper, zinc, molybdenum, boron, sodium and chlorine are identified as the essential micro nutrients for coffee. Among these elements, generally the coffee growing soils which are slightly acidic were known to be deficient only in zinc while others were present in optimum levels. Of late, the studies under taken by the research department have taken by the research department have shown that coffee growing soils are increasingly tending towards deficiency of micro nutrients, especially in zinc, boron and molybdenum. This may be due to the exclusively chemical fertilizer dependent agriculture practiced in recent times, lack of recycling of the farm wastes in the form of composts/organic manures and returning to the field, opening of the shade indiscriminately with short term interests of increasing production which in turn have exposed the soil to harsh conditions of nature (high temperature, heavy rain etc.,) and loss of its health. Micro nutrients, though required in micro quantities are essential nutrients and hence their deficiency affects the growth and performance of the plants.
Micro nutrients, though required in micro quantities are essential nutrients and hence their deficiency affects the growth and performance of the plants as they are directly involved in the nutrition of the plant. So, all the essential nutrients elements have to be supplied in adequate quantities to be sustain the growth and yield of the plants which in other words is called balanced have clearly shown that the foliar feeding of the deficient micro nutrients is more effective than their soil application.
When the soil are reported to have zinc, boron and molybdenum below the optimum levels or when the deficiency symptoms are observed on leaves, to counter the adverse effects of these deficiencies, one can resort to foliar sprays of these elements. Foliar spray solutions shall contain generally 500 g zinc sulphate, 50 g of ammonium miolybdate and 100 g of borax or boric acid. About 30 g of sprays lime of high purity is required to neutralize about 200 1 of spray solution can be sprayed per acre preferably during the posting-monsoon periods. The micro nutrients sprays are especially very effective and beneficial if given during the heavy cropping season. The point to be noted here is that exclusive foliar sprays cannot sustain the plant growth as well as yield and foliar feeding is not a substitute for ground application of nutrients in case of major nutrients.
Deficiency Symptoms of Nutrients
Non-application of balanced fertilizers and over exploitation without adequate nutrient supply generally results in deficiency of nutrients in plants. Recognizing the deficiency of the nutrients in soils much before expressed in leaves as discolouration or deformation can be done by comparing the available nutrient values obtained by soil test with the established nutrients threshold values. Deficiency symptoms of major and few micro-nutrient elements corrective measures and the threshold values of nutrients in soils and leaves are presented in tables. The discoloration and deformation of leaves due to specific nutrient deficiency is depicted in table.
Recycling of On-Farm Waste for Nutrient Management
Plants nutrient input is one of the important and major constraints of coffee cultivation in India. Harvesting the nutrient energy of biodegradable on-farm wastes is of prime significance for maximizing production. As the soil can degrade and assimilate the biodegradable wastes, their recycling by means of composting and returning to the soil not only reduces the chemical requirements of plants but also the pollution of streams/water sources by the direct disposal of wastes. Large potential for the exploitation of manorial values of biodegradable coffee plantations in the form of shade tree leaf litter, coffee leaves and pruning, weeded materials, fruit skin/pulp and cherry or parchment husks.
Under Indian conditions it is estimated that shade trees contribute roughly 10 t of leaf litter/ha annually that can contribute about 40 to 60 kg N, 30 to 33 kg P2O5 and 40 to 60 kg K2O to the soil on complete decomposition. In estates where ‘dadaps’ are used as temporary or permanent shades, the annual return of nutrients is around 96 kg N, 8 kg P2O5 and 67 kg K2O in the form of degradable stakes, tender branches and leaves. But in nature all the available bio-mass is not effectively recycled and there will be slow decomposition. The leaf litter acts as a soil cover and prevents the direct impact of rain water and thus reduces soil erosion. Similarly, coffee leaves shed by the plants, unyielding branches removed by handling and weeds collected after manual weeding, if returned to the field directly or after compositing, significant amount of nutrients will be imported back into the soil. The fruit skin/pulp obtained after pulping 600 kg of fruits returns 14 to 15 kg N, 3 to 3.7 kg P2O5, and 29 to 37 kg K2O to the coffee soil if properly decomposed and recycled. The cherry husk recycled after composing, contributes 1.66 to 2% N, 0.4 to 0.5% P2O5 and 2.4 to 2.6% K2O. the composts prepared on farm wastes can also be enriched with the biological agents like P soliloquizing bacteria, Trichoderma etc., by adding cultures to the composts at the fag end of the composting process. It is estimated that nearly 84 to 95 kg N, 40 to 42 kg P2O5 and 108 to 123 kg K2O are available for recycling in coffee field in a hectare per year besides ‘dadap’ wastes. Thus, recycling of all the farm wastes in the coffee plantations is strongly recommended for improving the production and quality of coffee. Recycling of all the farm wastes may help in reducing the fertilizer input costs and higher efficiency of applied matter content of the soil. These wastes are found to be superior to cattle manure in terms of nutrient contents. The characteristics of good compost are presented in the table.
Application of compost in coffee plantations once in two/three years at the rate of 2 to 3 t ac-1 is advisable for obtaining benefits of organic nutrients present in compost will be in organic form and as such will not be immediately available for the plants. Compost is a source of energy for the beneficial microbes present in soil. Hence the beneficial effect of compost on the soil physical, chemical and biological properties of the soil needs to be given importance rather than its nutrient content. The methodology for composting the on farm waste materials is discussed in chapter 15.
Bio-fertilizers, in strict sense, are not fertilizers which directly give nutrition to crop plants. These are cultures of micro-organisms like bacteria, fungi, packed in a carrier material. Thus, the critical input in bio-fertilizer is the micro-organisms. These micro-organisms help the plants indirectly through better Nitrogen (N) fixation or improving the nutrient availability in the soil. Bio-fertilizers can be defined as “microbial inoculants which contain live or latent cells of selected strains of nitrogen fixing, phosphate solubilizing micro-organisms used for application to seed, soil or composting areas to accelerate certain microbial processes; thus augmenting the availability of nutrients in easily assimilable forms to plants”.
Bio-fertilizers can be classified into three classes, viz., Nitrogen fixing, phosphorus mobilizing and organic matter decomposting. Rhizobium, Azotobacter, Azospirillum, blue-green Algae and Azolla are Nitrogen fixing bio-fertilizers. Bacillus, pseudomonas and Aspergillus niger are phosphate solubilizers while vesicular Abruscular Mycorrhizae (VAM) fungi are phosphorus absorbers. Among the organic matter decomposting bio-fertilizers two major types, namely, celluloythic and lignolytic are known.
The research studies conducted by CCRI from 1970s have clearly proven the beneficial effects of the various bio-fertilizers like Azospirillum, vesicular Arbuscular Mycorrhiza (VAM). Phosphorus Solubilizing Bacteria (PSB) etc., when used in nursery mixtures. The field trial conducted using a commercial product containing Pseudomonous striata, Aapergillus awamori, Candida sp. and Bacillus sp. on coffee yield and soil available phosphorus also has givemn encouraging results. The studies conducted on the performance of seedings bio-primed in the nursery also are indicting the positive effects of added bio-fertilizers have a potential to reduce the use of chemical fertilizers without reducing the quantum of production and thereby protecting soil and environment from pollution. The bio-fertilizers can play a major role in organic farming of coffee as they can be efficient nutrient sources to supplement the nutrients supplied through organic inputs.
Phosphorus Solubilizing Agents
Fixation of applied phosphorus is a serious problem in the acidic soils of coffee zones, which drastically reduces the availability of this major nutrient to coffee plants. Certain organic acids like citric acid and phosphorus solubilizing micro-organisms are known to help in release of fixed phosphorus in acid soils and thereby help in reducing the quantity of phosphorus fertilizers.
Citric Acid as Phosphorus Solubilizer
Citric acid is an organic, crystalline material and is found to be an active phosphorus solubilizer from both native and applied phosphorus sources. The soil applied phosphorus sources. The soil applied citric acid reacts with aluminium and iron phosphates (unavailable to plants) through complexional reaction and releases phosphate ions which react with hydrogen ions in the soil to form soluble phosphates which will be available for plants. Thus, citric acid renders the abundant active phosphorus fixing sites like aluminium, iron and manganese inactive in the soil and acts as p-soliloquizing agent laboratory and field studies have confirmed the efficacy of citric acid as P soliloquize by reducing P fixation rates in coffee growing soils. It is also found that availability of potassium and micronutrients, especially zinc, is enhanced by ground application of citric acid (1 to 1.5 kg ha-1) which can be mixed with NPX or NK fertilizers or sufficient quantity of sieved soil does not alter the soil pH and has no adverse effects either on plan or on soil properties.
Use of ‘P’ Soliloquizing Bio-Fertilizers
Application of 10 kg ha-1 of commercial bio fertilizer, (biophos) containing phosphorus soliloquizing bacteria, viz., armorial, Candida sp. and Bacillus sp. along with two thirds recommended dose of phosphatic fertilizer was found to improve the availability of P nutrient to coffee plants and also the crop yields.
Integrated Nutrient Management (INM) in Coffee
Strategies that promote optimal and efficient plant nutrition are required on a large scale in order to achieve higher production within the existing land resources. The aim should be to develop and adopt production systems that are productive, sustainable and least burdensome on the environment. Organic sources and recycling of farm wastes do not suffice on their own to make coffee cultivation sustainable. On the other hand, because of possible environmental concerns and economic constraints, crop nutrient requirements often cannot be met solely through mineral fertilizers. Hence, a judicious combination of mineral fertilizers with organic and biological sources of nutrients or in other words ‘Integrated Nutrient Management’ (INM) is being promoted. Such integrated applications are not only complementary but also synergistic as organic inputs have beneficial effects beyond their nutrient sources, be it the soil resources, mineral fertilizers, organic manures, recyclable wastes or bio-fertilizers.
Modern method of coffee cultivation brings about a lot of stress on the nutrient sink of the soil system. The high fertility status of the tropical virgin forest soils are dwindling due to exploitation. Use of newer high yielding varieties, thinning of the shade to achieve higher production, chemical fertilizer dependent agricultural practices clubbed with the absence of farm waste recycling strategies add to the problem. The non availability of chemical fertilizers, hike in their price etc. have further aggravated the problem and has forced the scientists and the growers to opt for INM which involves the judicious and combined use of different nutrient sources such as chemical fertilizers, organic manure and bio-fertilizers etc.
Nursery, green house and multi location field trials are being carried out to study the impact of INM on yield, quality of coffee and soil physical, chemical and biological properties. The results of the studies carried out so far have indicated the possibility of reducing the quantum of chemical fertilizers without sacrificing the yield and quality of coffee when substituted with organic manures and bio-fertilizers. Long term studies are necessary to recommend the INM package for perennial crop like coffee.