Real Time Nitrogen Management in Rice using Leaf Colour Chart under Rainfed Condition of Western Hills of Nepal

Rice is the most important staple food crops in Nepal occupying hectares of land producing 5045045 tomes of grains with national productivity of 3.39 t ha-1 (ABPSD, 2014). Rice is the major cereal crop of the terai and inner terai occupying 67.87% of total area (ABPSD, 2013) but can be grown throughout all agro-ecological regions from terai plains to the high hills up to 3000 mabove sea level (NARC, 2007) including valleys and foothills (Dhital et al., 1995). Rice provides 50% of total calories requirement to Nepalese population and contributes 20% to the agriculture gross development product (NARC, 2007).

The national yields (ABPSD, 2014) of rice (3.39 t ha-1) is far below the attainable yield of 5.00 t ha-1 (Dey and Hossain, 1995) and yield obtained in other major rice growing countries in the world. Furthermore this present yield of rice is not sufficient to meet the national demand. It is estimated that about 1259 thousand tons of additional rice need to be produced by 2030, which is equivalent to an overall increase of 27.96% in the next 17 years (Prasad et al., 2011; ABPSD, 2014). But the possibility of expanding the area in future is very limited. Therefore, the required extra production has to come only through increase in productivity with less water, labor, and chemicals and ensuring long-term sustainability. Agronomic management and technological innovations are needed to address these issues at present.

Among various reasons for this low productivity, inefficient utilization of nitrogen in considered to be the most critical one especially in south Asia including Nepal (Shukla et al., 2004; Witt et al., 2005). Nitrogen fertilizer must be applied only when necessary and must be based on the crops’ nitrogen status. However, most farmers rely on the age (days after transplanting) of rice and not on nitrogen status of crop (Alam et al., 2005). They generally apply nitrogen fertilizer infixed time recommended nitrogen split schedule and ratio at basal, maximum tillering and panicle initiation stages, without taking into account whether the plant really requires nitrogen at that time. The number of splits, amount of nitrogen applied per split and the time of applications vary greatly among the farmers (Witt et al., 2005; Regmi, 2003). This, consequently, caused inefficiency levels of nitrogen in terms of growth, development, and yield. Moreover, there are several farmers applying nitrogen fertilizer even if the crop does not need. As a result, there is an insignificant addition to the production cost and undesired effects on the growth of rice.

On the recent world-wide evaluation of fertilizer, its recovery efficiency has been found to be around 30% in rice (Krupnik et al., 2004). It has been observed that more than 60% of applied nitrogen is lost from the soil plant system due to lack of synchronization between the nitrogen demand and nitrogen supply (Yadav et al., 2004). The optimum use of nitrogen can be achieved by matching nitrogen supply with crop demand (Bijay et al., 2002) and caused greater yield responses to nitrogen application compared to farmer practice (Witt et al., 2005).

Viewing the scenario of low yield of rice in the hills of western Nepal, the experiment was conducted for sustainable improvement of the yield through the most economic and ecological prospective by effective nutrient management. The main objective of this study was to find out the effective nitrogen management practices through the use of LCC on rice production and to access the effect of different nitrogen management on growth, yield and yield attributes of rice under western mid hills of Nepal.