Nitrogen responses of barley grain and barley forage grown continually or after fallow
1988
Orphanos, P.I. | Metochis, Chr. (Agriculture Research Institute, Nicosia (Cyprus))
In long term experiment, barley was grown for grain, straw and hay. In all cases three N rates (0, 30, 60 kg N/ha) and two P rates (0, 20 kg P/ha) were applied in factorial combination. At the initial of the experiment the soil contained 50 ppm Olsen P, 400 ppm exchangeable K and 50 ppm NO3-N in the plough layer. Over the experimental years period 1980-88 rainfall was mostly below average. In only three years a significant amount of water was conserved - 70 mm in the soil fallowed. In contrast, substantial amounts of mineralized N accumulated in the soil fallowed when there was rainfall between the time the previous crop was harvested and the new crop was sown, up to 70 ppm NO3-N in the 45 cm layer. As a result grain yield after fallow was depressed, forage barley gave most stable yields; in the very dry 1985-6 season - 180 mm rainfall in which grain was not produced - 4 t/ha hay was produced. P application did not influence yield as expected. N application tended to decrease grain yield but to increase hay. It also increased N concentration in grain, straw and hay, and K concentration in straw and hay. The amount of N removed annually from unfertilized plots in the grain plus straw ranged between 0 and 99 kg/ha and that removed in the hay - 62 and 85 kg/ha. It is proposed that N fertilizer recommendations must be based on yield potential, rotation (incl. fallow), rainfall and N fertilizing during the preceding season. Soil NO3-N at sowing time is also useful but it may not be practically possible to determine
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