Balancing Sulfur and Magnesium Nutrition for Turmeric and Carrot Grown on Red Lateritic Soil

Abbreviations and notes for this article: N = nitrogen, P = phosphorus, K = potassium, Mg = magnesium, S = sulfur, Ca = calcium. The deficiency of secondary nutrients, namely S and Mg, is increasing in India. One survey found 240 districts to be generally deficient in S, and the problem is spreading (Sakal et al., 1981; Singh, 1998). A recent effort by the Fertiliser Association of India, The Sulphur Institute, and the International Fertilizer Industry Association (FAI-TSIIFA) studied 27,000 samples distributed over 12 states and found that over 40% of samples were deficient in available S and another 35% potentially deficient. More than 70% soil samples taken from Uttar Pradesh, Madhya Pradesh, Maharashtra, Orissa, Jharkhand, West Bengal, Andhra Pradesh, and Karnataka were low to medium in available S (Biswas et al., 2004). The main reasons behind such widespread deficiency are over-dependence on “S-free” fertilizers, depletion of soil S with continuous cropping, sizable areas (around 27% of the country’s gross cropped area) under pulses and oilseeds that have a higher requirement for S, loss of soil S due to leaching, soil erosion, lack of organic manure addition, and low awareness of farmers towards use and importance of S in agriculture. Similarly, Mg deficiency can be a problem in India. Cases are found in the acid laterite soils of Kerala, the Malnad area of Karnataka, Nilgiris in Tamil Nadu, certain areas of Andhra Pradesh under cotton, citrus, and banana, in Goa, parts of Himachal Pradesh, the red lateritic zone of West Bengal and throughout the northeastern region of India. Magnesium can be leached more easily compared to Ca, making acid, sandy soils particularly vulnerable to Mg deficiency. The deficiency also becomes severe under intensive cultivation. With heavy use of NPK fertilizers and manures, sometimes a depressing effect of K application on yield is the result of Mg deficiency. While possibly not a problem at low yields, Mg deficiency can become a problem at high yield levels, as in the case of tea estates in southern India (Verma, 1993). The Mg content of soils depends upon the nature of the parent material, the degree of weathering, soil texture, rainfall, intensity of cropping, and management practices. Magnesium deficiency is actually more widespread than is realized due to inadequate scientific data about the effect of applications of Mg fertilizers on crops, particularly in India. Birbhum district of West Bengal is located within the leached red and lateritic soil belt and has wide-spread N, P, K, S, and Mg deficiencies. The agro-climatic conditions in Birbhum are highly suited for cultivation of carrot and turmeric, but its soils require careful nutrient management for optimum yield. Two experiments were undertaken to study the effect of soil test based fertilizer application, with special reference to S and Mg, on growth, yield, and quality of carrot (cv. Early Nantes) and turmeric (cv. Lakadong, Shillong). Turmeric (Curcuma longa) is a herbaceous, rhizomatous spice crop, native to tropical Southeast Asia. India is the largest producer of turmeric in the world, with 75% of world output. Turmeric is a heavy nutrient using crop and responds well to fertilizer application. Carrot (Daucus carota L.) is one of the major vegetable crops of India. It is grown in the spring-summer season in temperate regions and during winter in tropical and subtropical parts of the world. Both the experiments were laid out in a randomized block design with seven treatments and three replications. In the case of turmeric the plot size was 7.0 m x 5.0 m, while for carrot the plot size was 3.5 m x 3.0 m. Uniform cultural practices and plant protection measures were undertaken for all the treatments. Randomly collected soil samples (0 to 15 cm depth) were analyzed and yield target-based recommendations were developed following Agro Services International, Inc. analytical methods (Portch and Hunter, 2002). All the plots in the turmeric experiment received 150 kg/ha N and 50 kg/ha P 2 O 5 and 190 kg K 2 O/ha on the basis of soil test values. For carrot, a constant level of 80 kg/ha N and 50 kg P 2 O 5 /ha and 120 kg K 2 O/ha were applied to all the plots on the basis of soil test values. Variable rates of S (0 to 66 kg/ha) and Mg (0 to 33 kg/ha) constituted the seven treatments for both the crops (Table 1). No S and Mg were applied in the control plots. Turmeric received the full dose of P during land preparation while half the N and K were applied one month after transplanting. The remaining N and K were applied 4 months after transplanting. Sulfur and Mg were applied in two equal Balancing Sulfur and Magnesium Nutrition for Turmeric and Carrot Grown on Red Lateritic Soil