engleski

Response of corn genotypes to phosphorus fertilization

In the continental part of Croatia there are favorable environmental conditions for corn (Zea mays L.) growing. However, yields of seed- corn are under more influences of environment in comparison with yields of hybrid corn, probably because seed-corn is more susceptible to abiotic stresses. Seven parents of corn hybrids (inbred lines: Os36-16, Os2-48, Os84- 44, Os138-9, Os89-9 Os84-49 i Os86-39) were grown under field conditions for three growing seasons (1993, 1994 and 1995.g) on three soils (S) as follows: the S-1 (acid soil), the S-2 (mineral amphigley) and the S-3 (low acid soil). By soil testing was found moderate P contents (EUF method, extraction 20oC: 1.45, 1.21 and 1.68 mg P/100 g of soil, for S-1, S-2 and S-3, respectively) and wide ranges of clay (19.1%, 51.3% and 33.6%, respectively) and pH (1nKCl) values (3.60, 5.30 and 4.40, respectively). They were applied four fertilization treatments. In this study was elaborated only two treatments as follows: a) control (ordinary fertilization: 180 kg N + 80 kg P2O5 and 120 kg K2O/ha) and b) a + ameliorative phosphorus fertilization (875 kg P2O5 as monoamonium phosphate MAP: 52% P2O5 and 12% N). P fertilization was made before corn sowing in the first year of testing, while in the second and the third year the field trials were fertilized as a control. The field experiment was conducted by split-plot method in four replicates (experimental plot for fertilization 300 m2 and for genotypes 40 m2). Nutritional status of corn was estimated by ear-leaf composition at beginning of anthesis. Grain yields were calculated on 14% grain mosture and theoretical plant density 49520 planst/ha (share of mother parent in seed-corn crop). Corn grain yield increase as affected by P fertilization was 42% (3-year means: 2.00 and 2.84 t/ha, for control and P treatment, respectively). At the same time, ear-leaf P was increased from 0.26% P (control) to 0.40% P. Growing season was more influencing factor (means 2.76, 2.78 and 1.77 t/ha, for the 1993, 1994 and 1995, respectively) in comparison with soil (means 2.34, 2.35 and 2.56 t/ha, for the S-1, S-2 and S-3, repectively). Grain yields (3-year means) of individual corn genotypes ranged from 2.16 t/ha (Os84-49) to 2.77 t/ha (Os84-44). Their ear-leaf P (3-year means) was in range from 0.310% P (Os36-16) to 0.345% P (Os86-39) with remarks that in remaining eigth genotypes it was similar (mean 0.327% P). Although corn responded to P fertilization, low connection was found between ear-leaf P and grain yield, probably because P status in corn were mainly in adequate level (from 0.25 to 0.50% P). Only low P in plants (mean 0.21% P) was found on the control of S-1. In general, fertilization practice for seed-corn is similar to corn hybrids. Based on our results, we recommend the higher rate of P fertilization for seed-corn crops, especially under low P supplies. In the future work could be elaborated some practical questions (for example, term of P application, broadcast and band placement etc.).

corn ; genotypes ; phosphorus ; fertilization ; grain yield ; soil

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