Effect of mineral fertilisation on the element uptake of maize (Zea mays L.) on chernozem soil. II.

The effect of different levels of N, P and K supplies and their combination s on the yield and mineral composition of maize (Mv 380) was examined on ca lcareous loamy chernozem soil. The soil had a pH(KCl) value of 7.3 and cont ained 5% CaCO3, 3% humus, poor supplies of P and Zn, moderate supplies of N and K, and satisfactory supplies of Ca, Mg Fe, Mn and Cu. The fertiliser w as applied in the form of 25% calcium ammonium nitrate, 18% superphosphate and 50% potassium chloride. The factorial experiment consisted of 4N x 4P x 4K = 64 treatments, with 2 replications. giving a total of 128 plots. The N rates were 0, 100, 200 and 300 kg/ha/yr, the P levels 0, 500, 1000 and 15 00 kg/ha/10 yr (P2O5) and the K levels also 0, 500, 1000 and 1500 kg/ha/10 yr. This replenishment P and K fertilisation took place when the experiment was set up in 1973. The forecrops used in the experiment were maize, wheat , wheat. Alfalfa was grown an the area for 4 years before the experiment wa s see up. The main conclusions are as follows: 1. As a result of the fairly wet winter preceding the vegetation period and the lack of hot dry winds in summer, the grain yield in 1977 was double th at achieved in 1976, reaching 8.2 t/ha on the unfertilised plots. Neverthel ess the total rainfall figures for the whole year and for the vegetation pe riod hardly exhibited any difference in 1976 and 1977. In 1977 the PxK supp lies determined the yield of young 6-leaf shoots and the NxK supply the gra in yield. The N1P1 levels and their combinations proved to be optimum. Over -fertilisation with P induced Zn deficiency, leading to a decline in the gr ain yield of 1.4 t/ha in 1976 and 1.0 t/ha in 1977. 2. The composition of leaf samples taken in the 6-leaf stage and at the beg inning of flowering/tasselling gave a satisfactory indication of the nutrit ional status of the plant. The optimum values recommended in the literature are suitable for use in the extension service, since they provide diagnost ic information. A P/Zn ratio in excess of 200 in any plant organ is indicat ive of Zn deficiency. 3. On this soil the Fe, Mn and Cu contents of maize can be modified to a gr eater extent through NxP interactions than by direct Fe, Mn or Cu soil fert ilisation. The stalk responded to the soil supplies with excessive uptake, accumulating 8 times as much P,7 times as much Cu and 3 times as much Mn at the same stalk mass. The Zn reserves dropped to a third on plots well supp lied with P. 4. A yield of 8.8 t/ha grain + 5.8 t/ha air-dry stalks contained a total of 171 kg N, 82 kg K (98 kg K2O), 47 kg P (108 kg P2O5), 40 kg Mg, 31 kg Ca. 1-2 kg Fe, 0.5 kg Mn, 0.24 kg Zn and 0.1 kg Cu on this soil. In 1976, due t o the severe drought, the same hybrid produced only 4.9 t/ha grain yield an d the specific macroelement quantity taken up by 1 t grain t the correspond ing stalk yield was 10-20% greater than that recorded in 1977. The mean Zn, Mn and Fe contents were 32%, 42% and 223% higher, respectively, in the dry year.