IMPACTS OF IRRIGATION AND GENOTYPE ON YIELD, PROTEIN, STARCH AND OIL CONTENTS IN GRAIN OF MAIZE INBRED LINES

Four inbred lines of maize (Os 438-95 = C1, Os 30-8 = C2, Os 6 = C3 and Os 1-44 = C4) were grown for 4-year period (2006-2009) in the stationary field experiment on Osijek eutric cambisol. Impact of irrigation, nitrogen fertilization and genotype were tested. Soil moisture was maintained by two irrigation rates from 60-100% and 80-100% of the field water capacity). Two steps of N (0, 100 and 200 kg N ha(-1)) were applied, while P and K fertilization was equal (500 kg/ha NPK 0: 30: 20). Eight maize genotypes (four inbred lines and four hybrids) were grown on each basic plot of fertilization. The experiment was duplicated for maize-soybean rotation. The experiment was set by split-split plot method according to randomized block design in three replicates. The basic plot areas were 617.2 m(2) (irrigation), 313.6 m(2) (fertilization) and 39.2 m(2) (genotype). Selection of N non-fertilized treatment and four inbred lines were made for this study with aim of testing year (A) irrigation (B) and genotype (C) effects under natural N-soil conditions. Average grain yield in level 1809 kg ha(-1) without N fertilization is indication of very high fertility of the soil. Differences of yield among the years were from 823 (2007) to 2450 (2006) kg ha(-1). Excessive drought and high air-temperature stress is responsible for the low maize yield in 2007. Irrigation considerable affected on maize yields (4-year averages: 1500, 1809 and 2118 kg ha(-1), for B1, B2 and B3, respectively). Differences of the 4-year average yields among the genotypes were from 1259 (C3) to 2765 (C1) kg ha(-1). Differences of yield among the genotypes in the different years were also considerable because the lowest yield was for 71% (A1), 23% (A2), 63% (A3) and 40% (A4) lower in comparison to the highest yield. The genotype effects under different water supplies were less influencing factor because the high-yielding C1 had for 128%, 129% and 106% the higher yield compared to the low-yielding C3, for