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The adaptability of twelve single cross maize hybrids was investigated at five different locations in Hungary over a three-year period. The characters examined were individual plant production (total mass of the ears on a single plant), thousand kernel mass, number of kernel rows, ear length, number of kernels per row, shelling % and the assimilating leaf area above the main ear.Among these yield components, the individual plant production, the ear length, the number of kernels per row and the grain-cob ratio (shelling %) were influenced to the greatest extent by the year, followed by the variety and the location. The greatest average yield was achieved by the tested hybrids at all five locations in 1997 (263 g/plant). The average yields in 1998 and 1999 were significantly lower (221 and 203 g/plant, respectively). The outstanding yields achieved in 1997 could be attributed to the favourable ecological conditions, which led to the development of secondary ears in Keszthely and Sopronhorpács. At the other three locations there was only one ear per plant, but these ears were longer than in the following years. The greatest year effect was recorded in Sopronhorpács, where the individual plant production amounted to 305 g/plant in 1997 and 238 g/plant in the worst year, 1999. In Gyöngyös conditions were very dry in all three years, so the year effect was least pronounced at this location (grand mean of 195 g/plant in 1997 and 201 g/plant in 1999). Stability analysis was carried out using the coefficient of variance for individual plant production. Hybrids Mv 3, Mv 5, Mv 9 and Mv 12 were found to have the best adaptability. The shelling % was not significantly influenced by the location; the grain-cob ratio is relatively stable for maize hybrids. A correlation was found between the individual plant production and the leaf area above the main ear (R 2 =0.66). Hybrids with the largest leaf area above the main ear also had the greatest ear mass.

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Some agronomical characters of twelve single-cross maize hybrids were investigated at five different locations in Hungary over a three-year period. The characters examined were individual plant production (total mass of the ears on a single plant), thousand-kernel mass, number of kernel rows, ear length, number of kernels per row, shelling % and the assimilating leaf area above the main ear. Among these yield components, the individual plant production, the ear length, the number of kernels per row and the grain-cob ratio (shelling %) were influenced to the greatest extent by the year, followed by the variety and the location. The greatest average yield was achieved by the tested hybrids at all five locations in 1997 (263 g/plant). The average yields in 1998 and 1999 were significantly lower (221 and 203 g/plant, respectively). The outstanding yields achieved in 1997 could be attributed to the favourable ecological conditions, which led to the development of secondary ears in Keszthely and Sopronhorpács. At the other three locations there was only one ear per plant, but these ears were longer than in the following years. The greatest year effect was recorded in Sopronhorpács, where the individual plant production amounted to 305 g/plant in 1997 and 238 g/plant in the worst year, 1999. In Gyöngyös conditions were very dry in all three years, so the year effect was least pronounced at this location (grand mean of 195 g/plant in 1997 and 201 g/plant in 1999). Stability analysis was carried out using the coefficient of variance for individual plant production. Hybrids Mv 3, Mv 5, Mv 9 and Mv 12 were found to have the best adaptability. The shelling % was not significantly influenced by the location; the grain-cob ratio is relatively stable for maize hybrids. A correlation was found between the individual plant production and the leaf area above the main ear (R2=0.658). Hybrids with the largest leaf area above the main ear also had the greatest ear mass.

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Inbred maize lines were treated with normal and double rates of post-emergence herbicides in a small-plot field experiment in one dry and one wet year. The chlorophyll a + b content of symptom-free ear-leaves was determined using a spectrophotometer after 50% silking in order to determine whether various rates of post-emergence herbicides had any effect on the chlorophyll content at flowering and how this was influenced by the type of year. The chlorophyll a + b content of the inbred lines was greatly dependent on the year, with values twice as high in the wet year as in the dry year. Treatment with tembotrione + isoxadifen-ethyl had no effect on the chlorophyll content in either year. Both rates of mesotrione + terbutylazine reduced the chlorophyll a + b content of one stress-sensitive inbred line in the dry year, but not in the wet year. In the wet year bentazone + dicamba increased the chlorophyll content, but only for one line was this effect significant irrespective of the dose. In the dry year the double dose caused a significant increase in this genotype, but the chlorophyll contents of the other lines did not differ significantly from the control.

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The relationship between the yield, chlorophyll content and leaf area index of five winter wheat genotypes was investigated in two different growing seasons on chernozem soil. The results suggest that the genotype and the nutrient supply had a considerable influence on both the yield and the physiological traits, while the growing season modified the parameters in a significant manner. The results proved that the chlorophyll content and leaf area index had a direct influence on the yield; varieties developing larger leaf area and leaf chlorophyll content had higher yields even in different seasons, but the yield was significantly influenced by the decline in the chlorophyll content after flowering. It could be concluded that studying the chlorophyll content and leaf area values simultaneously during the more important phenological phases (especially from flowering to the early period of grain-filling) makes it possible to predict the yield from the trends.

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The responses of Hungarian-bred maize hybrids with different vegetation periods to sowing date, N fertiliser and plant density were studied in small-plot field experiments between 2002 and 2004. The maize grain yield was highest in the early and optimum sowing date treatments (8.563 and 8.325 t ha-1) and significantly less in the late and very late treatments (7.908 and 7.279 t ha-1). The year had a substantial effect on both the yield and the grain moisture content. In a long-term maize monoculture experiment set up in 1961, the N fertiliser responses of 6 maize hybrids with different vegetation periods were investigated. Averaged over the years 2002 and 2004 the maize grain yields in the N treatments were as follows (t ha-1): N0: 4.780, N80: 7.479, N160: 8.577, N240: 8.226. The grain yield and yield stability of maize were greatest at a N rate of 160 kg ha-1. The yield response was similar in both years, but the year had a considerable effect on the yield level. The N supplies to maize plants during the vegetation period could be well characterised using a SPAD 502 chlorophyll meter in the R3 phenological stage (18-22 days after silking). The plant density responses of maize hybrids were described by fitting a quadratic function to the data of 19-22 hybrids in the years 2002-2004. The optimum plant density averaged over the hybrids was between 67,483 and 70,161 plants ha-1. The maximum yield associated with optimum plant density was 7.978 t ha-1 in 2002, 6.60 t ha-1 in 2003 and 9.37 t ha-1 in 2004. The annual patterns of plant density responses for the maize hybrids exhibited considerable differences.

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In a long-term experiment on continuous maize set up by Béla Győrffy in 1959, changes in biotic and abiotic environmental factors were studied over time. The long-term effects and stability of the cropping systems, the year effects and the genotype × environment interactions were analysed. The original aim of the experiment was to determine whether the NPK nutrients in farmyard manure could be replaced partially or entirely by inorganic NPK fertiliser. In the present experiment the effect of farmyard manure, mineral fertiliser and the year effect on yield and yield stability were studied for four years (2005–2008). Various levels of farmyard manure and mineral fertiliser induced significant changes in the yield, harvest index, thousand-kernel mass, grain number per ear and grain protein content.

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The effect of various fertiliser treatments on the yield of maize hybrids was studied on the basis of 26 years of data obtained in a long-term bifactorial split-plot experiment set up in 1967. The seven treatments (NPK ratio 2:1:1) applied were as follows (rates per hectare): 1. Control (no fertiliser), 2. 100 kg NPK, 3. 200 kg NPK, 4. 300 kg NPK, 5. 400 kg NPK, 6. 600 kg NPK, 7. 800 kg NPK. The maize was grown with the conventional cultivation techniques in continuous cropping. The results of analyses carried out with three different methods (analysis of variance, cumulative yield analysis and regression analysis) all indicated that under the given conditions the yield of maize hybrids was highest at an NPK fertiliser rate of 200-400 kg ha -1 . The effect of fertilisation on the maize yield was significant in 21 of the 26 years. Combined analysis of variance for the years showed that the year effect (quantity of rainfall) had the greatest effect on the maize yield, but although the year effect had a fundamental effect on the yield level it did not influence the fertiliser response pattern. The fertiliser responses of the maize hybrids were described by fitting four types of functions (quadratic, square root, inverse exponential, linear-plateau) to the yield data. It was found that when selecting the best function a consideration of the regression deviations (measured yield - calculated yield) was just as important as the coefficient of determination (R 2 ). In 12 of the 26 years the fitting of the quadratic function was not significant and overestimated the fertilisation optimum. The fertiliser response curve generally has a broad maximum which is far better described by the square root function than by the quadratic. If the fertiliser response pattern includes a depressive phase, a square root function should definitely be used in place of the quadratic function. If the maximum of the response surface forms a plateau (as opposed to a maximum point) a linear-plateau function or an inverse exponential function can be recommended. In the present work the linear-plateau function gave the best results.

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In a long-term maize monoculture experiment set up on the active ingredient equivalence principle, changes in the yield components were investigated over a period of three years (2005–2007) as a function of the fertiliser treatments, and the values of the growth parameters HI, LAI, NAR and CGR were calculated using the classical method of growth analysis.The results indicated that optimum N supplies and the year effect made a substantial contribution both to the grain number per ear and to the thousand-kernel weight. In the course of correlation analysis, both Pearson’s correlation coefficient and multiple regression analysis demonstrated that the grain yield was in close positive correlation with these yield components, and with the maximum value of dry matter production and the harvest index. The two yield components explained 76% of the grain yield, and the effect of thousand-kernel weight was around 3.75 times as great as that of the grain number per ear (β = 0.721 vs. 0.192). On the basis of partial correlation analysis, the maximum value of total dry matter and the thousand-kernel weight were jointly responsible for around 60% of the variance in maize grain yield. Analysis using the “Enter” method showed that the two yield components explained 62% and 59% of the grain yield in wet years (R2 2005 = 62.3%; R2 2006 = 58.8%), while in the dry year neither the thousand-kernel weight nor the grain number per ear had a significant effect on the yield (R2 2007 = 4.5%).

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The weed mass (g m −2 ) recorded in the first 15 years (1965–1979) of a long-term, bifactorial, split-plot herbicide experiment (main plots: two types of soil cultivation, subplots: 7 herbicide treatments, with two control plots) without crops indicated that the best weed control was achieved with 10 kg ha −1 rates of simazine and atrazine. These were followed by 5 kg ha −1 ametryn, 10 kg ha −1 linuron and 2+2 kg ha −1 2,4-D, all with moderate efficiency, while 5 kg ha −1 prometryn and 10 kg ha −1 monolinuron resulted in poorer weed control. Medium deep ploughing once a year in autumn reduced the weed mass by 36.5%. There was a substantial year effect, well illustrated by the annual changes in weed mass both in the herbicide treatments and in the control plots. In plots treated with simazine and atrazine there was an exponential increase in the weed mass from the 17 th year of the experiment, suggesting the multiplication of weed biotypes resistant to triazine. As a result of some herbicide treatments there was a shift in the monocot-dicot ratio.

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The effect of mineral fertilisation, farmyard manure and their combinations on the yield and yield stability of maize was studied in a long-term maize monoculture experiment set up in Martonvásár, Hungary in 1959. The experiment, laid out as a Latin square, included two fertilisation levels [35 t ha−1 or 70 t ha−1 farmyard manure (FYM) every four years] and seven treatments. The yield results were evaluated using analysis of variance, cumulative yield analysis and stability analysis. The year effect was analysed by dividing the 51 years (1959–2009) into wet (32) and dry (19) years. The rainfall sum for the months Apr.–Sep. averaged 361 mm in the wet years and 232 mm in the dry years.Among the fertiliser treatments the FYM + mineral fertiliser combination and NPK mineral fertilisation alone gave the highest yields. In more than 50% of the years the higher fertiliser level had no significant yield-increasing effect. The yield differences between the two fertiliser levels were twice as high in wet years as in dry years (0.543 vs. 0.274). Averaged over all seven treatments, the maize yield was 3.959 t ha−1 in dry years and 6.250 t ha−1 in wet years, giving a yield increment of 2.291 t ha−1 in favourable years. Yield stability was greatest when the NPK content of 35 t ha−1 FYM was replaced in part (17.5 t ha−1 FYM + N1/2P1/2K1/2) or in full (N1P1K1) by mineral fertiliser, or when 70 t ha−1 FYM was applied. Yield stability is an important indicator of the sustainability of crop production.

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