Different long-term experiments were carried on chernozem (Debrecen) and loamy (Hajdúböszörmény) soils. They included the most important agrotechnical, biological (hybrid) and agroecological (crop year, soil) factors in maize production. This paper evaluated the results of polyfactorial long-term experiments. For the maize the most favourable crop rotation was winter wheat (in a tri-culture) with an N 60-120, P 2 O 5 60-70, K 2 O and 90-110 kg ha -1 , and a density of 75-90,000 plants ha -1 . The different input levels of maize crop management systems can modify an adaptive capacity to ecological conditions and the resilience of agro-ecosystems. The optimalization of agrotechnical elements reduces the harmful climatic effects. The yields of maize varied between 2-11 t ha -1 in extensive and 10-15 t ha -1 in intensive crop management systems, respectively.

In order to enhance the adaptability and yield stability of maize, the effect of nutrient supply and plant density on yield was studied on a calcareous chernozem soil in Debrecen, while the relationship between sowing date and the grain moisture content at harvest was investigated on a typical meadow soil in Hajdúböszörmény.In the plant density experiment, the plant densities applied were 45, 60, 75 and 90 thousand plants/ha.The optimal fertilizer rates for the maize hybrids were: N 40-120, P 2 O 5 25-75, K 2 O 30-90 kg ha -1 . The application of NPK fertilizers in a wet year increased the yield by 40-50%. Hybrids with good chilling resistance at germination can be sown as early as 10 April, when the soil temperature reaches 8-10°C.There was a significant correlation between sowing date and the grain moisture content at harvest. When hybrids with good chilling resistance at germination were sown early, the grain moisture content at harvest was reduced by 5-10%.A plant density higher than the optimum reduces yield and yield stability. The optimal plant densities determined in the experiment were 60, 75 and 90 thousand plants/ha for two, three and one hybrid, respectively.

In this paper, we analysed the results of maize sowing time experiments conducted by the Department of Crop Sciences and Applied Ecology of the University of Debrecen Agricultural Sciences Centre, during the period from 1997-1999. We made the experiments at the experimental garden of DE ATC, on a chernozem soil with lime deposits.In 1997, we examined five hybrids, in 1998 six hybrids, and in 1999 three hybrids, with three sowing times. Sowing times were early (10. Apr. and 08. Apr.), optimal (25. Apr. and 28. Apr.) and late (15. May and 17. May). We examined the following standards: yield, seed moisture content at harvest, thousand kernel mass, duration of flowering, emergence time and profitability.In 1977, the emergence times, in order of sowing, were: 24, 12 and 9 days. Yields of the sowing times were the following, in mean, for the five hybrids: in the early sowing time (10. Apr.) 11,81 t/ha, in the optimal sowing time (25. Apr.) 11,67 t/ha, and in the late sowing time (15. May) 12,9 t/ha. The seed moisture content of the five hybrids at harvest was 8% less in early sowing time, than in the late sowing time. The thousand kernel mass was the biggest in late sowing time, but we could not prove any significant connection attributable to the effect of sowing time. We examinedprofitability, too. Of the five hybrids, four attained the greatest profit with the early sowing time in 1997.In 1998, the emergence times, in the order of sowing, were: 21, 10 and 11 days. Yields of the sowing times were the following, in mean, for the six hybrids: 08. Apr. 10,34 t/ha, 25. Apr. 11,02 t/ha, 15. May 11,52 t/ha. There were no significant differences between yields in 1998. The seed moisture content of the six hybrids at harvest was 7% less for the early sowing time, than for the late sowing time. In 1998, the profits were greatest for theearly and traditional sowing times.In 1999, the numbers of days from sowing to emergence were 18, 9 and 9 days, in the order of sowing times. Yields of the sowing times were the following, in mean, for the three hybrids: 13,25  t/ha, 12,51 t/ha and 12,34 t/ha, in the order of sowing times. The seed moisture content of maizes at harvest was 6% less with an early sowing time in the mean of all hybrids. In 1999, hybrid maizes gave big profits with early sowing times.Summing up the results of the three years, we can conclude that we get a significant yield increase and reduced seed moisture content at harvest if we apply the early sowing time, which can considerably increase the efficiency of maize cultivation.

BevezetésA kukorica a jövőben stratégiai növény lesz a világon és Magyarországon is. Az eddigi elsősorban élelmiszer és takarmány célú felhasználása mellett jelentős mértékben nőni fog az ipari felhasználása (ipari cukor, bioetanol, stb.). A kukorica vetésterülete a világon az utóbbi másfél évtizedben 25 millió hektárral nőtt, a hektáronkénti termésátlaga pedig 3,79 t/ha-ról 5,11 t/ha-ra növekedett, az összes termés 800 millió tonna felett van. A jelentős vetésterület növekedés a fosszilis energiát bizonyos mértékig helyettesítő bioetanol gyártással hozható összefüggésbe. A kukorica termésátlagát alapul véve Magyarország a világ rangsorában az 5. helyet foglalja el (1. táblázat).1. táblázat: A világ élvonala a kukoricatermesztésben termésátlag alapján, 1 millió ha feletti területtel rendelkező országok adatai szerint (FAO adatok, 2008.)

No abstract