The influence of crop density on the photosynthetic characteristics and productivity of the spring oilseed rape under non-fertilized and fertilized conditions

Abstract

The objective of the investigation was to determine the optimal density of spring oilseed rape (Brassica napus L.), including the photosynthetic characteristics, that would ensure the maximum realization of rape biological potential and the highest seed yield under non-fertilized and fertilized conditions. Field experiments were carried out during the 2008–2010 growing season at the Experimental Station of the Aleksandras Stulginskis University (54°53' N, 23°50' E). Treatments of the experiment were: factor A fertilization (1) without fertilizers, 2) with fertilizers (before rape sowing N 64, P2O5 64 and K2O 94 kg ha-1 and at the budding stage N 70 kg ha-1) and factor B crop density: 1) 2 kg ha-1 (50.1–100 plants m-2), 2) 4 kg ha-1 (100.1–150 plants m-2), 3) 6 kg ha-1 (150.1–200 plants m-2), 4) 8 kg ha-1 (200.1–250 plants m-2), 5) 10 kg ha-1 (250.1–300 plants m-2), 6) 12 kg ha-1 (300.1–350 plants m-2), 7) 14 kg ha-1 (350.1–400 plants m-2) and 8) 16 kg ha-1 (400.1–450 plants m-2). In the crop without fertilizers the highest rape seed yield was obtained at a crop density of 300.1–350 plants m-2 and in the crop with fertilizers – at a crop density of 100.1–150 plants m-2. In the crop without fertilizers rape seed yield depended on the photosynthetic potential of the crop (r = 0.80, P < 0.05), net assimilation rate (r = 0.73, P < 0.05) and productivity of rape at the flowering stage (r = 0.83, P < 0.05). In the crop with fertilizers rape seed yield was influenced by penetration of photosynthetically active radiation on ¼ (r = 0.73, P < 0.05) and ½ (r = 0.74, P < 0.05) height of the crop stand, number of branches per plant (r = 0.98, P < 0.01), number of pods per plant (r = 0.98, P < 0.01) and number of seeds per pod (r = 0.72, P < 0.01).