Fertilizer Requirements 61 Fertilizer scheduling

As stated earlier, cardamom is being grown in the rich fertile soils of forest eco-system. Up to the middle of fifties, it was cultivated without any manuring or limited to organic manures, if at all applied. As importance of this spice crop was increasingly felt in the national and international market scenario, its cultivation was taken up in a more systematic and scientific manner and many of the planters started applying chemical fertilizers. de Geus (1973) suggested a fertilizer dose of 45:45:45 kg N, P2O5 and K2O/ha for Kerala, 67:34:100 kg N, P2O5 and K2O/ha for Karnataka with half N in organic form and 45:34:45 kg N, P2O5 and K2O/ha for Tamil Nadu. However, considering the low requirement of cardamom and the high status of N and K in cardamom-growing soils, a maintenance dose of 30:60:30 kg N, P2O5 and K2O/ha was recommended for healthy and vigorous growth of plants (Zachariah, 1978). Based on further studies and the factors affecting the availability of nutrients in the soil, a fertilizer dose of 75:75:150 kg N, P2O5 and K2O/ha was recommended under rainfed situation for a normal crop of 100 kg dry capsules/ha. If the yield is more, the fertilizer doses are to be increased proportionately. Additional fertilizer dose of 0.65 kg N, P2O5 and 1.30 kg K2O/ha is to be applied for increase in yield of every 2.5 kg dry capsules over normal yield (Anonymous, 1976; Kologi, 1977). Results of recent studies (Srinivasan et al., 1998) indicated that significant yield increase and savings in fertilizer requirements would be possible by way of soil-cum-foliar application method. In Karnataka, N, P2O5 and K2O @37.5:37.5:75 kg/ha through soil and 2.5 per cent urea + 0.75 per cent single super phosphate + 1.0 per cent muriate of potash through foliage gave 64 kg yield increase/ha over no fertilizer application. The yield increase recorded was 43 kg/ha under Tamil Nadu conditions, where the dosages required were 20:40:20 kg N, P2O5 and K2O/ha through soil and 3 per cent urea + 1 per cent single super phosphate + 2 per cent muriate of potash through foliage. In irrigated plantations, the general fertilizer recommendation is to apply N, P2O5 and K2O at the rate of 125:125:250 kg/ha to soil in three splits (Anonymous, 1997). Kumar et al. (2000) also suggested application of NPK @ 75:75:150 kg/ha under Karnataka conditions for increasing yield of the crop. Urea was found to be the best source for N compared to ammonium sulphate (Deshpande et al, 1971). For cardamom-growing soils, being rich in organic matter and acidic in nature, mussoriephos was found to be the ideal fertilizer source for P (Nair and Zachariah, 1975). When plant population is increased to 5000/ha under trench method of planting, fertilizers are to be applied at the rate of 120:120:240 kg N, P2O5 and K2O/ha (Korikanthimath, 1986), which was subsequently revised as 150:75:300 kg N, P2O5 and K2O/ha (Korikanthimath et al, 1998a). Under low rainfall situations prevailing in the Lower Pulney tracts of Tamil Nadu, a fertilizer dose of 40:80:40 kg N, P2O5 and K2O/ha is recommended (Natarajan and Srinivasan, 1989). Later on Srinivasan and Bidappa (1990) worked out nutrient models for P and K based on adsorption isotherms. The total phosphorus requirement (TPR) of soil was arrived at as TPR (kg/ha) = (60 — x) X 3.24 where 60 is the desired soil fertility level for P, x is the soil test value for P and 3.24 is a constant derived from the model taking into account of bulk density, weight of soil/ha etc. The Total Potassium Requirement worked out was TPR (kg/ha) = (300 — x) X 2.64, where 300 is the desired soil fertility level for K, x is the soil test value for K and 2.64 is the constant. The models aim at maintaining soil P and K levels at 60 and 300 kg/ha as these levels are considered to be optimum for cardamom. Ranganathan and Natesan (1985) reported beneficial effect of application of zinc sulphate to nursery plants by incorporating it along with fertilizer mixture. Sivadasan et al. (1991) found that application of 500 ppm zinc sulphate to yielding plants on foliage not only enhanced growth and yield but also quality of produce. Deshpande et al. (1971) found the beneficial effect of liming of cardamom soils in correcting acidity and enhancing the rate of nitrification resulting in better growth. However, subsequent observations (Nair et al, 1988; Anonymous, 1997) indicated that liming is not required as a routine practice in cardamom plantations. Fertilizer schedule is given in Table 5.1.

When application of fertilizer through soil is resorted to, it would be necessary to give one-third of the recommended dose (75:75:150 kg/ha of NPK) during the first year of plant growth both under rainfed and irrigated conditions. During the second year of plant growth, the dose may be increased to one-half of the recommended dose (75:75:150 and 125:125:250 kg NPK/ha for rainfed and irrigated conditions respectively) and fertilizers at full dose may be applied from third year of plant growth onwards (Anonymous, 1993).

All the above fertilizer recommendations are based on the conventional analytical techniques and not based on more recent concepts such as the nutrient buffer power. Application of this concept to K requirements led Nair et al. (1997) to suggest that a thorough reorientation of the nutrient schedule in cardamom is essential.

Organic manures are considered essential for improving physical characteristics of soil, apart from their nutritional values, and they are indispensable for cardamom irrespective of whether fertilizers are applied or not. Application of organic manures such as neem cake (1—2 kg/plant) or farmyard manure or cow dung compost at the rate of 5 kg/plant may be made once in a year in May—June along with mussoriephos and muriate of potash (Anonymous, 1997). Thimmarayappa etal. (2000) suggested an integrated nutrient management to meet the 25 per cent of requirement of nitrogen

Table 5.1 Fertilizer schedule for cardamom

Region

Soil application

Soil-cum-foliar

Time of application

+3 -1

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