Soil and atmospheric nitrogen uptake by lentil (Lens culinaris Medik.) and barley (Hordeum vulgare ssp nudum L.) as monocrops and intercrops

Three morphologically different varieties of lentil (Lens culinaris Medik.) and one cultivar of naked spring barley (Hordeum vulgare ssp. nudum L.) were studied as monocrops and in a substitutive mixture in a 2-year field experiment. Plants were grown on a brown warp soil in the temperate climate of Central Europe. The growth habit of the lentil type (spreading or erect habit) had no marked influence on growth, soil N and atmospheric N-2 acquisition of monocropped and intercropped lentil. Yield advantage of the mixture over both monocrops was only apparent in one year when mineral soil N (N-min-N) was low. The yield advantage of the barley-lentil mixture seems to be based on two effects: the greater crop growth rate (CGR) of barley in the early growth period due to the efficient use of soil N-min-N which compensates for the lower CGR of lentil in the early growth stages and the N-2 fixation of lentil which compensates for the nitrogen limitation in the soil so that the CGR of the mixture reaches the CGR of monocropped lentil in later growth stages. At maturity the level of symbiotically fixed N-2 was 154/117 kg N ha(-1) (2000/2001) in monocropped lentil and 95/41 kg N ha(-1) in intercropped lentil. The amounts of N taken up from the soil were 58/61 kg N ha(-1) (2000/2001) and 17/8 kg N ha(-1) for monocropped and intercropped lentil, respectively. Monocropped lentils took up N-min-N almost exclusively from the top 0.6 m soil layers and showed a great N sparing effect. At final harvest monocropped lentil left up to 52 kg N-min-N ha(-1) more in the soil than intercropped lentil and barley. Harvest indices of DM and N of the crop stands increased in the order: monocropped lentil < mixture < monocropped barley. The N balances of the crop stands were in the reverse order. The higher Nmin-N supply and the drier growth conditions in 2001 increased uptake of N from soil by barley, the competitive ability of barley in the mixture and the harvest indices of all crop stands and led to a reduction in N balances. It was concluded that under a temperate climate, high N use efficiency in legume-based cropping systems can be achieved by managing the cereal-lentil intercrops to enhance the symbiotic N-2 fixation without reducing the soil N uptake efficiency. It can also be achieved by growing follow-on crops before winter which have a high nitrogen uptake ability to minimize the risk of losses from the high residual N-min-N left after growing monocropped lentil. (C) 2003 Elsevier B.V. All rights reserved.