Nitrogen, a vitally important plant nutrient, is subject to various losses that affect its efficiency. We tested prilled urea (PU), urea supergranules (USG), green manures (GM) and farmyard manure (FYM) in a rice-wheat cropping system to determine which were the most efficient and economical N sources. The maximum rice growth, yield and N-uptake occurred with USG and with GM (Sesbania rostrata) plus PU. Incorporation of GM saved 60 kg N/ha. On the following wheat crop, GM (S. aculeata) plus PU and FYM plus PU had the highest residual effect on the number of tillers per m2, and straw and grain yield. An increase in N recovery efficiency occurred with combined use of PUand organic Igreen manures compared with PU alone. In areas where USG is costly or unavailable and FYM is scarce, green manures can be a cheap N source that allows small-scale farmers to get sustainable yields in a rice-wheat rotation.

Two experiments were conducted to investigate the effect of supplementation with fodder tree leaves on the utilization of teff straw. This ivas aimed at testing the hypothesis that forage supplements (e.g. sesbania) that disappear faster from the rumen compared with those that disappear slowly (eg. leucaena) may elicit higher intakes of the basal diet. Experiment 1 investigated the effect of level (i.e. 0,200,300 and 400 g/kg dry matter (DM) intake) of leaves of Sesbania sesban or Leucaena leucocephala on the utilization of teff straw fed ad libitum. Seven sheep were given the seven diets in four periods following a partially balanced (7 × 4) cross-over design. In experiment 2, teff straw alone or supplemented with graded levels of sesbania (250, 350 and 450 g/kg DM intake), were fed to 16 sheep in a completely randomized block design. Intake, degradability, nitrogen (N) utilization, particulate and liquid passage rates were estimated.

In experiment 1, protein source × protein level interaction was not significant. Supplementation increased intakes of total DM (P < 0-05), organic matter (P < 0·01) and N retention (P < 0·01) but had no effect on the intake of teff straw. Supplementation with sesbania, but not with leucaena, increased (P < 0·05) the apparent digestibility of DM. Both supplements increased (P < 0·05) the fractional rate of passage from the rumen. In experiment 2, graded levels of sesbania increased DM intake (P < 0·05), fractional rate of liquid outflow (P< 0·05) and tended to increase the rate of degradation. It was concluded that the effect of fodder tree leaves on roughage intake is a function of their disappearance rate from the rumen.