In recent experiments researchers have succeeded in increasing the ANRE (Apparent nitrogen-recovery efficiency)in double rice from 0.2 kg plant N kg^-1 fertilizer N in the farmer’s fertilizer practice to 0.3 kg kg^-1 using site-specific nutrient management (SSNM). Despite these recent technological developments, there is still space for improving N-use efficiency in rice. Apparent recovery rates of SSNM are 0.3 kg plant N kg^-1 fertilizer N, while with good management it is possible to achieve rates of 0.5-0.6 in irrigated rice. These rates could be reached through an even more real-time N management. We computed nitrogen requirements and losses for apparent N-recovery rates of 0.4 and 0.5 to gain insight of the consequences of the development and adoption of such technologies for environmental sustainability. The results show that a lot can be gained from these technologies. An increase of the apparent N-recovery of 0.3 to 0.4 results in a decrease in total nitrogen losses of 32 percent for double rice and 25 percent for single rice. A further increase to 0.5 would result in another decrease of 14 and 16 percent points for double and single rice, respectively.
Fertilizer recovery rates are even lower for horticultural production than for rice. we used TechnoGIN to compute potential technologies for the common rotation of greens-celery-rice. We increased the ANRE from 0.14 in farmer practice to 0.20 and 0.25 assuming that yields remain the same. Like SSNM techniques in rice,these changes could be achieved by fine-tuning fertilizer gifts to crop requirements. The results of our computations are promising: An increase of the ANRE from 0.14 to 0.20 would result in a decrease in nitrogen fertilizer of 32 percent and a decrease in nitrogen losses of 29 percent. A consecutive increase of the ANRE to 0.25 would imply another decrease in nitrogen costs by 14 percent points and nitrogen losses by 16 percent points. These computations indicate that there is ample scope for the introduction of new technologies that are beneficial for farmer income as well as the environment.