Nitrogén, réz és molibdén kölcsönhatások lucerna kultúrában (Medicago sativa L.)
Authors: Kádár Imre 
Published: December 2017

Interactions between the elements N, Cu and Mo were studied on alfalfa in 1996-1999 in a field experiment set up on chernozem loam soil with lime deposits. The ploughed layer of the soil contained 3% humus, around 5% CaCO3 and around 20% clay. Soil analysis showed that the area was well supplied with Ca, Mg, K and Mn had satisfactory Cu content, but was only poorly or moderately supplied with P and Zn. The groundwater depth was 13–15 m and the area was prone to drought. The experiment was originally set up in a split-plot design with 4N × 3Cu = 12 treatments in three replications, giving a total of 36 plots. The N rates, applied as calcium ammonium nitrate, were 0, 100, 200 and 300 kg·ha−1 and the Cu rates, in the form of CuSO4, were 0, 50 and 100 kg·ha−1. In the 5th year of the experiment the 15 m long plots were halved and the two half-plots were separated by a 1 m path. The experiment thus became a strip-split-plot design, consisting of 4N×3Cu×2Mo = 24 treatments in three replications, giving a total of 72 plots. The 48 kg·ha−1 Mo was applied in the form of (NH4)6Mo7O24·4H2O. The main results were as follows:

In this chernozem loam soil the N, Cu, Mo treatments did not affect the yield of alfalfa. During the four years studied (1996–1999), a total of 32 t·ha−1 of hay was harvested, with maximum yields (4–5 t·ha−1) at the first mowing. Considering the years, the 2nd year of alfalfa was the most successful with a yield of 11 t·ha−1.

With increasing rates of N, the incorporation of N, NO3-N, Ca, Mg, Na, and sometimes Cu increased, while that of K decreased in the hay. Due to the 10–12-year residual effect of CuSO4 the original Cu content of the hay improved by 30–50%, i.e. 2–4 mg·kg–1.

A single dose of 48 kg·ha−1 Mo raised the hay Mo content by an order of magnitude to 18–69 mg·kg–1 even after 5–8 years. The Mo content decreased with age and the number of mowings. Nevertheless, the hay became unsuitable for use as animal feed. Mo fertilization also influenced the incorporation of other elements, demonstrably increasing the uptake of N, Ca and Mg and moderating that of K, NO3-N and Cu.

As a specific catalyst for the N-binding microorganisms in the soil, Mo is able to increase the soil N supply and thus the N content of the plants. Mo is also necessary for NO3 reduction, so the quantity of NO3-N is reduced through incorporation into proteins in response to Mo. In the present experiment, N-Mo and N-Cu synergism and Mo-NO3 antagonism were manifested.

Due to the influence of the different years, mowings and treatments, the minimum and maximum element contents of the hay varied over a wide range. In 12 mowings over the course of four years a total of 1190 kg N, 787 kg K, 768 kg Ca, 154 kg Mg, 128 kg S, 102 kg P, 12 kg Na, 8 kg Fe, 5 kg Al, 4 kg Sr and 2 kg each of Mn and B was taken up per hectare, together with 416 g Zn, 288 g Ba, 256 g Cu and 96 g Mo per ha. The uptake of Mo was 1131 g·ha−1 on Mo-treated soil.

The specific nutrient content of 1 t hay was 37 kg N, 25 kg K, 24 kg Ca, 5 kg Mg and 3 kg P (7 kg P2O5). N abundance was associated with elevated specific nutrient content under the given experimental conditions. On this soil atmospheric N fixation was able to cover the N requirements of alfalfa.