Poljoprivreda (Dec 2000)
RESPONSE OF CORN INBRED LINES TO FERTILIZATION AND SOIL TYPE IN EASTERN CROATIA
Abstract
Seven corn (Zea mays L.) 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 soil types of eastern Croatia as follows: pseudogley (Sesvetačko polje, PPK Kutjevo d.d.: acid soil), pseudogley gley (T-12 Prv~a jug, PPK Nova Gradiška d.d: low acid soil) and mineral amphigley (T-8 Orubica, PPK Nova Gradiška d.d.: amphigley). Fertilization treatments were carried out as follows: a) control (ordinary fertilization: 180 kg N + 80 kg P2O5 and 120 kg K2O/ha), b) a + 875 kg P2O5 in form of monoamonium phosphate (MAP: 52% P2O5 and 12% N), c) a + 875 kg K2O in KCl form (60% K2O), d) a + 875 kg P2O5/ha + 875 kg K2O/ha. Meliorative fertilization with phosphorus and potassium was made before corn sowing in the first year of testing, whereas in the second and the third year the field trials were fertilized only by ordinary fertilization. The field trials were conducted in four replications. Corn inbred lines properties were determined by our testing as follows: grain yield; nitrogen (N), phosphorus (P) and potassium (K) concentrations in ear-leaf at the beginning of silking stage; share of female-sterile plants, shares of grain in corn cob and grain moisture in the harvest period. Mean grain yield in our 3-year testing was 2.63 t/ha. Depending on year it ranged from 1.94 t/ha (1995) to 3.00 t/ha (1993), depending on soil type from 2.44 t/ha (acid soil: Sesvetačko polje) to 2.80 t/ha (low acid soil: Prvča-jug), depending on genotype from 2.40 t/ha (Os2-48 and Os84-49) to 2.97 t/ha (Os84-4) and depending on applied fertilization from 2.00 t/ha (control) to 2.91 t/ha (meliorative fertilization by P and K). Eear-leaf N, P and K concentrations (% in dry matter: 3-year means) were as follows: 2.30%N, 0.35% P and 2.01% K, respectively. Depending on a year they were from 2.12%N (1995) to 2.63% N (1993), from 0.31%P (1993) to 0.38%P (1995) and from 1.93%K (1993) to 2.07 %K (1994), depending on soil type from 2.21%N (acid soil) to 2.39%N (amphigley), from 0.28%P (acid soil) to 0.40% P (amphigley) and from 1.76%K (amphigley) to 2.15%K (acid soil), depending on a genotype from 2.24%N (Os89-9) to 2.46%N ((Os84-44), from 0.34%P (Os36-16 and Os138- 9) from 0.37% P (Os2-48 and Os86-39) and from 1.96%K (Os2-48 and Os86-39) to 2.07%K (Os84-44) and depending on fertilization from 2.22%N (control) to 2.36%N (P and K meliorative fertilization), from 0.27%P ckontrol) to 0.40%P (P and PK meliorative fertilizations) and from 1.60%K (control) to 2.22%K (PK meliorative fertilization). Growing season 1995 was less favourable for corn growing, while remaining two were somewhat more favorable. For this reasons, mean grain yields were different depending on the growing season. Especially low yields were achieved on amphygley soil in unfavorable 1995 growing season (mean yield only 1.33 t/ha) and it is by 60% lower in comparison with two previous years on the same soil (2-year mean: 3.29 t/ha). These conditions could be designated as environmental stress, while by analogous comparison for acid soil and low acid soil, were found only by 14% and 25% lower yields, respectively. Under stress condition on amphygley during 1995 growing season, effects of applied fertilization were mutualy similar and yield were only for 16% higher than on control treatment. However, in the previuos "normal" growing seasons, grain yield on fertilized treatments were on the average by 57% higher in compariosn with control. The highest grain yield on amphygley (the growing season 1995) was found for Os84-44 genotype (1.50 t/ha), and it was also the most yielding genotype on remaining two soils. Also, by this genotype higher yields were found by 41% on amphygley soil and 28% on low acid soil (3-year means) as affected by meliorative fertilization. In comparison with ordinary fertilization (3-year means), phosphorus fertilization was more effective on acid soil (35% higher yield), application of both elements were more effective on amphygley (56% higher yield), while on low acid soil applied fertilizations were of similar effects (44% higher yield). Based on our results it is needed to recommend higher fertilization for seed-corn crops, especially when they are grown on soils that are moderately supplied with tested nutrients. Applied fertilization affected ear-leaf P and K concentrations. In general, these influences were more pronounced in the second and third year of testing (1994 and 1995) , while in the first year of testing (1993) it was either low or without effect. We presume that these responses are due too late meliorative fertilization (it was made in spring of 1993 and fertilizers were incorporated in soil only by presowing soil tillage treatments). Ear-leaf N status was less depended on P and K fertilization. In general, considerable differences of ear-leaf N, P and K status were found by our testing among different corn genotypes under identical environmental conditions.
