RESULTS OF THE RESEARCH ON THE INFLUENCE OF SOWING DATE ON THE CHEMICAL COMPOSITION OF MAIZE GRAIN AT

. Climate changes, more prominently visible in recent years, have alerted scientific research and, implicitly, the agricultural sector, which is most affected by these changes. Maize, is one of the most widespread field crops in our country, is also the most exposed to atmospheric and soil drought pronounced in the summer months. In this context, we initiated and tested the following experimental variants: earlier sowing, when in the soil, at a depth of 10 cm, 6 °C is achieved, sowing in the optimal period, at 10°C in the soil and sowing after the optimal period, following the evolution of both American and Romanian hybrids. The temperature evolution during the vegetation period of the crop, in the three years of the study, did not show significant differences, the influence on the change in the chemical composition of the grains was not obvious. The evolution of precipitation was fluctuating over months and years. The studies focused on the influence of the sowing season on the production and quality of corn grains in the area of the Research and Development Station for Cattle Breeding Târgu Mureș (RDSB Târgu Mureș). According to the data recorded in the 2018-2020 agricultural years, in the geopedological conditions of the Sângeorgiu de Mureș area, the studied hybrids responded well to early sowing, and the composition of the grains did not register substantial changes. The polyfactorial experiment was realized in the years 2018, 2019 and 2020 in the experimental field of the Plant Laboratory at RDSCB Târgu Mureș, according to the method of subdivided plots, the first factor the sowing date, with 3 gradations: the first sowing date, an early sowing was realised when 6ºC were recorded in the soil; the 2nd sowing date, an optimal sowing date when 10ºC was achieved in the soil and the 3rd sowing date, two weeks after the 2nd. Factor 2 is represented by the 4 tested corn hybrids.


INTRODUCTION
sowing date, an optimal sowing date when 10ºC was achieved in the soil and the 3rd sowing date, two weeks after the 2nd. Factor 2 is represented by the 4 tested corn hybrids. The hybrids used two hybrids from SCDA Turda: Turda 248 (FAO 300) and Turda 332 (FAO 380) and two hybrids from the company Pioneer, P 9900 (FAO 360) and P9903 (FAO 360).
Was used sowing density of 65,000 harvestable plants per ha, with the distance between rows at 70 cm. Field work was done by harrowing in August, deep plowing in the autumn, leveling discs in the spring and a work with the combine to prepare the germinative bed.
The application of the whole dose of fertilizers was done after disk, and their incorporation into the soil was done with the combinater. The amount and type of fertilizer used were N16P16K16 500 kg/ha, and every three years 4 t amendments per ha were applied.
The soil on which the experiment was located, it was a brown forest soil, weakly podzolic, clay loam texture, with a humus content of 1.9, pH of 5.8, P2O2 supply is 17.4 mg/100g soil, K2O 21 .7 mg/100 g soil and an N index of 1.4. The predecessor plant was soybean.
The results of the studies were analyzed according to the climatic conditions of the area, recorded at the weather station in Sângeorgiu de Mureș and presented in Figures 1 and 2.
The temperature evolution during the vegetation period of the crop, in the three years of the study, did not show significant differences, the influence on the change in the chemical composition of the grains was not obvious.
From the recorded data, it is highlighted that the average monthly temperatures during the vegetation period of the crop (April-October), during the studied years (2018-2020), exceeded the multi-year average. The average temperature during the 2018-2020 vegetation period was 17.1ºC, exceeding the multiannual average for the respective period by 2.2 °C.
Data valorization was carried out by analysis of variance with one factor and/or two factors (Săulescu and Săulescu 1966), and the calculation of simple correlations and the coefficient of variability, according to Ceapoiu (1968).

RESULTS AND DISCUSSIONS
The number of days with soil temperatures below 10ºC and the number of days between sowing and emergence differed between sowing seasons and years. Thus, in the early sowing season, an average of 12 days with temperatures below 10°C were recorded, and the number of days between sowing and emergence was 17, in the optimal sowing season, an average of 9 days with temperatures below 10°C and a number of 17 days in the period from sowing to emergence, and in the late season 2 days with temperatures below 10°C and a number of 11 days between sowing and emergence.

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The climatic conditions during 2018-2021 were different, with quite long periods, especially in April, with soil temperatures below the minimum threshold for germination. The most unfavorable years were 2019 and 2020 when the number of days with temperatures below the germination threshold reached 17, in the early period, resulting in the extension of the period until the emergence of corn, between 18 and 21 days. So as the number of days with temperatures below 10°C decreased, so did the number of days from sowing to emergence.
The analysis of variance in table 2 reveals the presence of significant and distinctly significant differences within each of the studied characteristics, as a result of the variability of the hybrids studied, the climatic conditions and the sowing season. n.s. -insignificant; *; ** significant la P=5%, p-1% For the protein content, a significantly positive difference was found between the hybrid and the year-season interaction and insignificant for the year, the year-hybrid interactions, the sowing season and the hybrid-season.
For the percentage of starch, significantly positive differences were highlighted for year and year-hybrid interaction, and distinctly significantly positive for hybrid f and the sowing season, and no significant differences were highlighted for the year-season and hybrid-season interactions.
For the fat percentage, a distinctly significant positive difference between the hybrids was revealed, and for the other factors and interactions, no significant differences were reported ( Table 3).
The influence of the sowing time, year, hybrid on the content and amount of protein, starch and fat, from Table  3, showed that the time of sowing did not results significant differences in protein content, neither percentage or quantity. A distinctly positive difference was found in the starch content in sowing season III, but in the amount of starch the differences were insignificant. No significant differences were reported in the fat content at all sowing season. The analysis of the year on the grain quality indices (protein, starch, fat) showed that the percentage of protein did not register significant differences, only for the amount of protein, a significantly positive difference was recorded in 2019 and a significantly negative difference in 2020. The percentage of starch was not influenced by the year, and for the amount of starch a distinctly significant positive difference was recorded in 2018 and a significantly negative difference in 2020.
The analysis regarding the influence of the hybrid on the quality indices, in the case of the protein content revealed a significantly negative difference in the hybrid P9903, in the case of the amount of protein, a very significantly positive difference was recorded in the hybrids P9900 and P9903, and in the hybrids T332 and T248 there was a very significantly negative difference. For the percentage of starch, a distinctly significant negative difference was recorded for the P9900 hybrid, a very significantly positive difference for the P9903 hybrid, and for the amount of starch, a very significantly positive difference was recorded for the P9900 and P9903 hybrids, as well as a very significantly negative difference for hybrids T332 and T248.
From the analysis of the amount of protein per hectare, it emerges that there were significantly negative differences only for the T248 hybrid in sowing season I, in the sowing season -hybrid interaction (Table 4). In the fat content, a significantly negative difference was highlighted in the P9903 hybrid and a significantly positive one in the T248 hybrid, in the amount of fat, a significantly positive difference was recorded only in the P9900 hybrid, in the other hybrids the differences were not statistically ensured.
Following the research of Buriro et al. (2015), it was found that all quantitative and qualitative traits of maize were negatively influenced by late sowing and positively by early sowing.
According of protein percentage, following the interaction of sowing season -year on protein content, a significantly positive difference was found in sowing season I in 2020, and in the analysis of the amount of protein/hectare in sowing season III in 2020, a significantly positive difference was also found. The other combinations were not statistically covered (Table 5). Maize being the crop with the largest weight in animal feed, we performed the statistical calculation in percentages and kilograms per surface unit. The evaluation of the data regarding the influence of the sowing period on the protein percentage in the four hybrids of different origin highlighted that only in the P9903 hybrid there were distinctly significantly positive differences in the sowing season III, in the other three hybrids no differences were reported either in sowing season I or in sowing season III.
Following the research of Butts-Wilmsmeyer et al. (2019) found that grain yield potential and grain quality are correlated and strongly influenced by environmental factors such as temperature, total rainfall and soil water storage.
The analysis of the sowing date on the percentage and amount of starch in the analyzed hybrids highlighted the fact that there were significantly positive differences regarding the percentage of starch at the T248 hybrid, at the late sowing date. For the amount of starch/ha, a significantly positive difference was found at the hybrid P990 at the late sowing date, and a distinctly significant negative difference was found at the hybrid T248 (Table 6). As for the starch content, following the sowing season -year interaction, significantly positive differences were found in sowing season III in 2018. Also, significantly positive differences were found in sowing season I and III in 2020. When analyzing the amount of starch per hectare, a significantly positive difference was found only in sowing season III in 2020 (Table 7).  Moentono (1989) and Menddhe (1992) reported that grain yield/plant, 1000-weight and yield increased in early sown maize.
The calculation of the correlation between grain production and the quantity in kilograms of the components of the grain is necessary to know, being also useful in the composition of fodder rations in animal husbandry.
In the case of the 4 hybrids analyzed in the experiment and cultivated in 3diferent sowing dates during 2018-2020, distinct and very significantly positive correlations were identified between the studied elements.
Nagy (2009) stated in his studies that there is a negative correlation between yield and protein content and that very large differences in protein content are found between early and late sowing. In the case of starch, he states that late sowing of hybrids of the FAO 200 and FAO 400 groups significantly, negatively influences grain content.  Table 8 shows the results of the correlation coefficients between grain production and some of their quality components. Values with very significantly higher meanings were recorded between grain production and starch content (0.99), fats (0.83) and protein (0.89). Between the protein and starch content (0.89) the correlation coefficient recorded a very significantly higher significance and between protein and fats (0.73) distinctly significantly superior. For fats and starch the correlation coefficient (0.80) registered a significantly higher significance. 0.89 *** 0.73 ** 1.00 Grain production kg/ha 0.99 *** 0.83 *** 0.89*** 1.00 *r-P5%=0.58; **r-P1%=0.71; ***r-P0.01%=0.82

CONCLUSIONS
The research results from the three years of experimentation reveal the fact that sowing below the optimal germination temperature did not substantially change the composition of the grains, neither the time of sowing nor the year recorded significant decreases in the percentage of protein and starch compared to the optimal time of sowing.
The early sowing date did not reduce the percentage of plants that emerged compared to the optimal sowing date, but it influenced the dynamics of emergence in the sense that it increased the number of days with suboptimal temperatures.
The research years 2018-2020 did not change the percentage of protein, starch and fat, but they had an important influence on the percentage amount of the qualitative indices analyzed.
The hybrid factor represented the factor with the greatest differences, explained by the different genetics of the hybrids. In P9903 hybrids; P9900 and T332 did not find a decrease in the content and quantity of protein/ha and starch at early sowing.
Early sowing date does not substantially change protein, starch and fat content, identification of good Cold Test hybrids is required for early sowing under minimum soil temperature of 6 °C at sowing.