A. Megyes et al., Effect of mineral fertilisation on the yield of the maize (Zea mays L.) hybrid Dekalb 471 SC under irrigated and non-irrigated conditions, NOVENYTERME, 49(3), 2000, pp. 307-316
In a long-term field experiment set up in the Latokop experimental station
of the Centre of Agricultural Sciences of Debrecen University, the data of
the last five years (1995-1999) were analysed to determine the crop product
ion factors with the greatest influence on maize production and the correla
tions and interactions between irrigation and mineral fertilisation. The ex
perimental results were evaluated using analysis of variance.
In the extremely dry year of 1995 mineral fertilisation was found to cause
substantial yield depression in the absence of irrigation. According to the
results of analysis of variance mineral fertilisation significantly reduce
d the maize yield by 40-90% compared to that of the control plot. Under irr
igated conditions there was a considerable increase in the maize yield, the
yield surplus being 4.4-9.4 t/ha, depending on the nutrient supply level.
The greatest irrigation effect was recorded on plots fertilised with 120 kg
/ha N, while at a rate of 240 kg N/ha the efficiency of irrigation was extr
emely low and the yield was almost 3 t/ha lower than that achieved with the
lower, 120 kg/ha rate of N, and was practically the same as that recorded
on the unfertilised control plots.
During the period from 1996-1999, when the rainfall conditions were favoura
ble for maize, mineral fertilisation significantly increased the maize yiel
d even without irrigation over the average of the four years. The yield sur
plus due to mineral fertilisation was 3.9-4.6 t/ha, depending on the fertil
isation rare. The maximum yield surplus was obtained on plots fertilised wi
th the lower N rate of 120 kg/ha. At a rate of 240 kg Nka the maize yield d
id not differ significantly from this value. During the period examined the
yield was significantly higher at all three nutrient supply levels as the
result of irrigation than in the non-irrigated treatment. As in the case of
non-irrigated conditions, the highest fertiliser dose did not result in a
substantial yield increase. An analysis of the interaction between fertilis
ation and irrigation indicated that the yield-increasing effect of fertilis
ation was not significantly different under irrigated and non-irrigated con
ditions. The significant year x irrigation interaction was confirmed by the
fact that the yield surplus (1.3-2.3 t/ha) differed greatly from the irrig
ation effect recorded in 1995.
The results indicate that there is no justification for applying 240 kg N/h
a, plus the corresponding P and K fertilisers, since this dose does not inc
rease the maize yield significantly compared with the 120 kg/ha rate and in
dry years may even lead to a substantial yield reduction. This rate of N f
ertilisation is definitely excessive and its application will have a negati
ve effect on the profitability of maize production, leading to serious loss
es. In addition it is a potential source of danger From the point of view o
f environment protection, since high doses of N fertiliser combined with ir
rigation multiply the quantity of nitrate leached from the root zone to pol
lute the,groundwater.