The interactions between potassium and boron were examined on adobe soil in the Nagyhörcsök Experimental Site of the HAS RISSAC in the second experimental year in 1989 with maize as indicator crop. The amount of basic fertilisation was 100 kg ha-1 N and 100 kg ha-1 P2O5. K levels were adjusted with fill-up doses of 0, 1000, 2000 kg ha-1 K2O, while the B doses were 0, 20, 40, 60 kg ha-1 in the autumn of 1987 after alfalfa green crop. Fertilisers were applied in the form of CAN, superphosphate, 60% KCl and 11% borax. The three K levels served as main plots and the four B levels were the basic plots with 12 treatments, three replications and 36 plots in a split-plot design.

The ploughed layer of the production site contains around 5% CaCO3, 3% humus and 20–22% clay. Originally, the soil was well endowed with N, Ca, Mg and Mn, moderately supplied with K and relatively weak in P an Zn. The groundwater level is 13-15 m and the production site is drought sensitive. There was 266 mm rainfall over the nearly 6 month long growing season of maize and the 1 m soil layer probably contained 160-180 mm more available water stock at the time of sowing. There was no precipitation in September which accelerated the ripening process and drying off of maize, resulting in yield limitation. Main conclusions and results:

1. As a result of the 60 kg ha-1 B dose applied two years before, the maize shoot mass of at the 4-6 leaf stage decreased by one third, while the grain and stem yield at harvest reduced by 1.5 t ha-1 on average. B toxicity was also reflected by each yield element (grain number per ear and grain weight). The number of infertile ears also significantly increased from 1.6% to 5.6%.

2. On average, the B content of the grain and stem yield became three times higher on the fertilised soil, 7 times higher in the leaf at the silking stage and nearly 8 times higher in the shoot at the 4-6 leaf stage. There was a significant yield decrease when the B concentration of the 4-6-leaf shoot reached the 70-80 mg kg-1 level and that of the leaf reached the 100 mg kg-1 level at the silking stage. At the same time, the B content of the grain at harvest was above 10 mg kg-1 and that of the stem was between 15-20 mg kg-1.

3. The 1-2 t ha-1 K2O refill 2 years before resulted in a 0.5 t ha-1 grain yield surplus on average on an adobe soil well-moderately supplied with potassium and it partially counterbalanced B toxicity. As a result of the increased potassium supply, the K content of the vegetable parts increased and the amount of incorporated Ca and Mg cations decreased at the same time.

4. The average 6.9 t ha-1 grain yield incorporated 160 kg N, 85 kg K, 18 kg Ca, 26 kg P and 14 kg Mg with the associated 4.4 t ha-1 stem yield. Our data could serve as a guideline of technical advice when calculating the element content of the planned yield.

5. The quantity of ammonium lactate+acetous soluble AL-K increased 2.5 times in the ploughed layerd with the highest K refill in the second experimental year. The hot water soluble B content increased nearly 7 times as a result of the 60 kg ha-1 B dose applied. There was no significant increase in the deeper, 20-40 and 40-60 cm layers.

Keywords: potassium, boron, interactions, maize, soil and plant analysis