Above-ground growth dynamics and net production of spring barley in relation to nitrogen fertilization. Crop development, nitrogen uptake, nitrogen content, harvest index, yield components and harvest residues

Detailed studies of growth were made on spring barley over a 4-year period in central Sweden. Two barley treatments were cultivated from 1980 to 1985 on the same plots. One treatment was fertilized with 120 kg N ha-1 (B120) while the other received no nitrogen (B0). Above-ground parts were sampled and analyzed for nitrogen content. In addition, phenological development, plant density and canopy height were recorded. The green areas of various assimilating plant parts (i.e. leaf laminae, sheaths, ears and awns) were estimated in 1985. Net above-ground primary production was calculated in two ways while nitrogen uptake was estimated as the annual peak in above-ground nitrogen. Depending on the calculation method, mean annual above-ground net production of ash-free dry mass in B12 and B0 during 1982-1985 ranged between 799-844 and 350-406 g m-2, respectively. The average above-ground nitrogen uptake in B0 was only one third of that in B120, or about 5 and 15 g m-2 yr-1 respecitvely. In comparison with B120 (868 stems m-2, 753 ears m-2 and 19.6 grains ear-1), the unfertilized treatment produced less stems (502 m-2), less ears (424 m-2), and less grains per ear (15.7 ear -1), and the canopy was lower. Both the harvest index and nitrogen harvest index were lower for B0. However, neither phenological development nor the mean weight per grain were affected by the lack of nitrogen fertilizer input. In 1985, due to a long period of drought, net production, grain yields, canopy height and green area index were lower than during previous years in both treatments. The drought affected nitrogen uptake and numbers of grains per ear negatively in B0 but not in B120. This was attributed to the shallower root distribution in B0. Total net primary production and total nitrogen uptake (including below-ground parts) were calculated. Average annual net production of organic matter in B120 and B0 was 939 or 983 and 450 or 506 g m-2, respectively, depending on the calculation method used. Below-ground production constituted about 15 and 20% of total production in B120 and B0, respectively. Total nitrogen uptake was 17 and 6.5 g m-2. The total soil input of organic matter via stubble, spillage and roots was 296 and 210 g m-2 in B120 and B0, respectively. The corresponding amount of nitrogen returned to the soil was 5.0 and 2.8 g m-2.