The formation of the leaf surface of white melilot (Melilotus albus) depending on fertilization, seed mix and seeding rate

Abstract

The study objective was to analyze the formation of the leaf surface of white melilot (Melilotus albus) cultivated in pure sowing and mixes with annual cereals, with varying seeding rates for this species and varying fertilization levels. White melilot was sown in pure sowing and mixes with maize, millet, Sudan grass, and sorghum, with four seeding rates (16, 18, 20, and 22 kg ha–1). Four doses of fertilization with NPK were used in the investigations (0 – control treatment without fertilization, N45P45K45, N60P60K60, and N60P90K90). The leaves’ surface was assessed through scanning on the 30th, 40th, and 50th day after the germination of white melilot and in the period of its readiness for mowing (64th day). White melilot leaves were separated from the stems and placed in a transparent folder with a 25 cm calibration square, then scanned with a flatbed scanner in black-and-white mode. The obtained image was analyzed in Areas software, the built-in analytical tools of which were used to determine the area of the scanned leaves. After determining each plant’s leaf surface, the mean for each variant of the experiment was calculated, and then, using the concentration of plants per 1 m2, the mean M. albus leaf surface per hectare was obtained. The investigations demonstrated that the surface of white melilot leaves varied depending on the mix’s component, the seeding rate for this species, and the fertilization doses. Depending on the seeding rate (16, 18, 20, and 22 kg ha–1), one plant’s mean leaf surface area was as follows: 0.014115, 0.013955, 0.013824, and 0.013654 m2. The smallest M. albus leaf surface area per hectare was recorded in treatments without components (pure sowing) and with the highest seeding rate for this species’ seeds. The significantly the largest leaf surface area was observed in treatments where M. albus was sown in 16 kg ha–1, in a mix with Sudan grass and maize. Millet was the component with the strongest negative effect on this parameter, with each of the M. albus seeding rates used. Typically, the studied species’ leaf surface area was successively decreasing by 2 to 11% as the seeding rate increased. When mineral fertilizers were introduced, the species under study's leaf surface area was increasing by 7 to 16% as the fertilization rate increased. Considering the mean values for the study period, the largest area of white melilot leaves (in the period of readiness for cutting) was recorded in a mixed treatment of white melilot with Sudan grass, i.e., 52.3 thousand m2 ha–1 with fertilization of N60P90K90 and seeding rate of 16 kg ha–1.