Effects of farmyard manure (FYM) and chemical fertilizer in crop biomass [total net production (TNP)], yield, and root necromass were studied in a tropical dryland rice-lentil rotation agroecosystem. Total net production of rice which was greater than that of lentil increased significantly with exogenous nutrient inputs. During both crops aboveground net production (ANP) was recorded till the final harvest but no belowground net production (BNP) was recorded after the grain or seed-forming stage. Compared to the control, enhancement of TNP in rice was comparable for fertilizer (32%) and FYM (30%) treatments, but in lentil FYM showed a greater effect (43%) compared to fertilizer (29%) application. Grain or seed yield accounted for about 11% of TNP in both crops. Similar to TNP, rice yield showed a greater response to fertilizer (50%) compared to FYM (44%) while lentil yield responded more to FYM (43%) than to fertilizer (21%). Farmyard manure application resulted in greater necromass accumulation compared to fertiliser application. Rice contributed the major portion of root necromass in the crop land. While root necromass increased through the rice crop period, it decreased consistently through that of the lentil crop.