RICE is one of the most important cereal crops and is a major export commodity. But the average rice yield per acre here is low compared to that of other rice-producing countries. An important reason for this low yield is imbalanced nutrient management.

Our farmers use macronutrients like nitrogen, phosphorus and potash without knowing the requirement of their soils. Boron is an important micronutrient which is deficient in our soils. It is one of the most important nutrients for rice crop throughout its growth cycle. Boron deficiency is ever-increasing as a result of intensive cropping and non judicious use of fertilisers.

Boron deficiency, among other micronutrients, has a serious impact on crop productivity because of intensive cropping and imbalanced use of macro nutrients.

We are not adding the much needed micronutrients to our soils. Boron is relatively immobile in rice plants and not retranslocated to new growth, and therefore its deficiency symptoms usually appear first on young leaves. In case of boron deficiency, young rice leaves show white and rolled tips and death of growing points. The plant is also dwarfed due to its deficiency.

If the deficiency occurs at the panicle formation stage the plant fails to produce panicles. In fine varieties of rice, increasing sterility is the main problem, which is due to boron deficiency. The deficiency occurs in highly weathered, acid-red soils, sandy rice soils and acid soils.

Boron is also very important in improving kernel quality. Starch contents, grain size, shape and strength is increased by applying boron at proper time. Starch contents are very important for increasing cooking quality of rice.

With the insufficiency of starch in rice kernels, stickiness after cooking increases which is undesirable. Its uptake in higher plants is closely related to the pH and boron concentration in the soil solution and is probably a passive process.

The list of possible role of boron is long, including sugar transport, cell wall synthesis, lignifications etc. This long list might indicate, either that boron is involved in a number of metabolic pathways.

Boron availability generally decreases as soil becomes dry. Therefore, boron deficiency is more likely in plants suffering from water deficit. This may be because plants encounter less available boron when they extract moisture from soil at a lower depth during dry conditions.

Wetting and drying cycles increases the amount of boron fixation. Many researchers have suggested that the level of soil organic matter influences the availability of boron to plants. However, there is little information about the role of organic matter in boron nutrition.

If the plant and soil analysis show its deficiency, then following management practices should be adopted. Excessive leaching should be avoided as boron is very mobile in flooded rice soils. On boron deficient soils, apply slow-acting boron sources (e.g., colemanite) at intervals of two to three years. Boron fertilisers have a longer residual effect in salty and clayey soils (2-3 kg boron per ha should be applied) than in sandy soils (apply 3-5kg boron ha-1). In rice-wheat systems, boron applied to wheat can alleviate boron deficiency in the subsequent rice crop. Apply boron in soluble forms (borax) for rapid treatment of boron deficiency (0.5-3 kg boron ha-1), broadcasted and incorporated before planting, top dressed or used as foliar spray during vegetative growth. Borax and fertilizer borates should not be mixed with ammonium fertilisers because this will cause NH3 volatilisation.

Excessive amounts of boron should not be applied to avoid boron toxicity. If boron is at toxic level then plant shows symptoms like Chlorosis of tips and margins of older leaves as initial symptoms and dark brown elliptical spots on discolored areas two to three weeks later followed by browning and drying up.

The general measures to prevent boron toxicity include use of boron toxicity tolerant varieties Use surface water with low boron content for irrigation. Groundwater must be monitored regularly if used for irrigation. If the boron concentration is too great, dilute with water from a different source containing a small amount of boron.

Mostly rice is produced in our country by transplanting nursery in puddled field which is maintained at flooded condition up to physiological maturity. But as the world water resources are shrinking rapidly so the flooded rice is in process of shifting to aerobic condition.

Direct seeded rice, alternate wetting and drying etc., are under studies and becoming popular. This shifting may also cause the problem for boron uptake which leads toward more pollen sterility and thus lower resultant yield.

Extension wing should try to create awareness about the significance of boron fertilisation in rice along with identification and mitigation of its deficiency. Agriculture officers should be provided facilities to visit each and every farmer at his door step and guide him about use of boron. Farmer meetings, field days and formal and non-formal education can also be used effectively in this context.

Furthermore, credit facilities and incentives should be given to farmers along with technical guideline about when, how and how much boron should be applied. Electronic and print media should also play their role by conducting programmes with close eye on creating awareness about boron use and its management.

Dose of boron can be set according to the different rice cultures. The element should be included in nutrient management system when planning about rice nutrition so that higher outcome can yield benefits to our farmers and our country can earn a significant foreign exchange through export of quality rice.