Fertilizer use in Bangladesh
 

Table 1. Nutrient use in Bangladesh, 1980/81 to 1995/96 ('000 tons) Nutrient   1980/81   1985/86   1990/91   1995/96   1980/81 to 1995/96 Growth (%) Nitrogen (N) 265.0 365.7 609.9 942.8 9.0 Phosphate (P2O5) 118.0 136.9 239.2 157.7 2.0 Potassium (K2O) 27.0 35.8 89.5 93.5 8.5 Sulphur (S) 0.0 0.8 20.9 89.5 35.0* Total NPKS 410.0 539.2 959.5 1283.5 8.0 * Growth since 1990/91

Table 1 shows the growth in nutrient application for selected years, from 1980/81 to 1995/96.
The figures were extracted from the Fertilizer Recommendation Guide-1997, published by the Bangladesh Agricultural Research Council (BARC). According to BARC, there are approximately 12 million hectares (ha) under cultivation in Bangladesh, yielding a simple nutrient application rate of 108 kg per hectare per year, well above India (80 kg per hectare per year) and Thailand (61 kg per hectare per year), but far below China (309 kg per hectare per year) and Malaysia (158 kg per hectare per year). This rate of nutrient application also compares unfavourably to the rate of nutrient removal by Bangladesh's major crops. Rice removes 304 kg per hectare per crop, jute 509 kg per hectare, and sugarcane 643 kg per hectare per crop.

Soil nutrients and limiting factors
Soil nutrients are replaced through other means than fertilizer application, most notably during the annual floods and through the application of manure, but the rate of replenishment is relatively low. Even when nutrients are present in the soil, their availability to the crop may be limited. For example, almost six million of Bangladesh's 12 million cultivated hectares are strongly acidic, a condition that reduces phosphate availability.
Nitrogen is the most important nutrient for crop growth and productivity, and every farmer is rightly concerned that his crop is not nitrogen deficient. The amount of nitrogen that the crop can effectively use is influenced by the availability of other nutrients, and additional nitrogen application could be a waste of money when low phosphate and potassium levels could inhibit nitrogen efficiency. When a crop cannot reach its full potential yield because of nutrient shortage, that shortage is called the limiting factor.

The balanced fertility goal
The goal of a balanced fertilizer programme is to ensure that the growth and yield of the crop are not limited by an absence of plant nutrients. A well-conceived balanced fertilizer programme would consider the available soil nutrients, the nutrients removed by the crop, the potential yield of the seed hybrid, and the inherent fertility of the particular field to determine an annual management plan. This plan would include fertilizer application rates and timing and would include other fertility recommendations, such as a pH adjustment to increase nutrient availability.
The long-term goal of a balanced fertilizer programme is to maximize the productive capability of the land. The programme may address crop rotation patterns, irrigation and drainage issues, seed hybrids, or pest control -- virtually every aspect of crop production.

The balanced fertilizer programme
The ideal balanced fertilizer programme begins with a soil test to establish existing phosphate, potassium and sulphur nutrient levels and measures other soil characteristics such as pH, and organic matter content. Critical micronutrients, namely zinc or magnesium, could also be measured depending on the crops to be planted.
Soil nitrogen is commonly not measured, as it is highly mobile and subject to leaching, and a measure at a point in time may not be a good indication of the nitrogen that would be available at planting.
The fertilizer supplier and the farmer review the soil test and annual fertility development plan for the field. The amount of fertilizer to be applied is determined by the fertilizer recommendation for that crop, which in turn is based on the crop's nutrient requirements compared to the nutrients already available in the soil. A recommendation would include information on the timing of applications, particularly nitrogen applications. A proper recommendation is designed to correct any limiting factors that would reduce potential yield.
Once the fertilizer application and timing have been agreed, the dealer calculates the fertilizer blend and rate of application. Blends are commonly identified by their nutrient content, always read in the order nitrogen-phosphate- potassium-sulphur-micronutrients. A blend labelled 10-17-24-6-1Zn-1Mg would contain ten per cent nitrogen, 17 per cent phosphate, 24 per cent potassium, 6 per cent sulphur, 1 per cent zinc, and 1 per cent magnesium. By convention, the phosphate content of fertilizer is expressed as P2O5, instead of elemental phosphate, and the potassium content is expressed as K2O, instead of elemental potassium.
After the fertilizer has been applied, the supplier and the farmer are required monitor the crop as it grows to identify other factors, such as pest problems or weather conditions, that affect the yield. At harvest, the farmer and the dealer should obtain an accurate yield measurement in order to evaluate over time, the effectiveness of the programme. An accurate yield measurement also acts as a guide to the amount of nutrient removed, which may affect the amount of fertilizer applied to the next crop.

ATDP's support of balanced fertilizer
ATDP began its investigation into the question of balanced fertility in February 1998, with a survey of fertilizer practices and a seminar on the importance of balanced fertility. In 1999, ATDP increased its efforts by working directly with suppliers interested in producing blended fertilizer.
ATDP has assisted interested suppliers with information and promotional support, and has produced a handbook with information on starting and operating a successful blended fertilizer business. For more information on blended fertilizer and balanced fertility, readers are requested to contact:
Agrobased Industries and Technology Development Project (ATDP), International Fertilizer Development Center (IFDC), House 103, Road 1, Block F, Banani, Dhaka 1213, Tel: 9882008-9, 887404; Fax: 988 1724, e-mail: atdp@citechco.net.