Effect of leaf area on the yield of maize in a fertilization experiment

The yield of maize may be influenced by many factors (water and nutrient deficiency, etc.), all of which affect the leaf area, the most important site of photosynthesis. The achievement of an increase in the photo-synthetically active leaf area could thus have a very favourable effect on the potential yield. One way to increase the photo-synthetically active leaf area is to improve nutrient supplies to the plant. The experiment was small-plot mineral fertilisation trial in a random block design. In the two experimental years (2001, 2002), five fertilisation levels were applied in three replications besides the control, the lowest fertiliser rate being 40 kg N, 25 kg P2O5 and 30 kg K2O and the highest five times greater (200, 125 and 150 kg N, P2O5 and K2O, respectively). The individual leaf area was measured five times in 2001 on maize hybrids PR36R10, Katinka, Florencia and DK 557, and four times in 2002 on hybrids PR39K08, PR37M81, Mv Maraton, PR36R10 and DK 557. Measurements were carried out in the control (without fertilisers) and in replications I-III at the 1st (N 40 kg/ha), 3rd (N 120 kg/ha) and 5th (N 200 kg/ha) fertilisation levels. The width and length of the leaves of living plants were measured, and the individual leaf areas were calculated using the Montgomery formula. The results of the experiment were processed using variance, correlation and regression analyses with the statistical programme SPSS for Windows 9.0. The hybrids reached maximum leaf area by the middle or end of July in 2001. Under control conditions, the leaf area was only 1.65-2.09 m(2)/m(2) in 2001. With an increase in the nutrient supplies, the leaf area increased considerably The first fertiliser level (40 kg/ha N + PK) had the most pronounced effect on leaf area, which increased to 2.90-3.84 m(2)/m(2). The leaf area did not increase so sharply with further increases in the fertiliser rate, but the maximum LAI values of 3.08-3.92 m(2)/m(2) were reached at higher fertiliser levels. The hybrids reached maximum leaf area as early as the middle of June in 2002. Under control conditions the leaf area was slightly more favourable in 2002, with LAI values of 1.74-2.53 m(2)/m(2). It was again the first fertiliser rate (40 kg/ha N + PK) that had the greatest effect on leaf area, leading to LAI values of 2.98-3.93 m(2)/m(2). On the basis of regression analysis, it could be concluded that the effect of the leaf area index (LAI) on yield was very strong. Despite the fact that the LAI values differed in 2001 and 2002, there were no significant differences between the effects of weather conditions in the two experimental years; the correlation was very close (R-2 values: 0.69582 and 0.61330, respectively). The Pearson correlation was calculated in the course of correlation analysis. A close positive correlation was observed between the leaf area and the yield for all the hybrids in 2001 and 2002.