Mg. Mason et al., EFFECT OF AN ACIDIFYING NITROGEN-FERTILIZER AND LIME ON SOIL-PH AND WHEAT YIELDS .2. PLANT-RESPONSE, Australian journal of experimental agriculture, 34(2), 1994, pp. 247-253
This paper reports the effects of an acidifying fertiliser on wheat yi
elds and mineral composition in the first 10 years of trials at Merred
in, Wongan Hills, and Newdegate, described in the previous paper. Ther
e were grain yield increases from application (kg/ha.year) of 17.5 N 7.6 P and 35 N + 15.2 P in all years except 1980 (Wongan Hills and Ne
wdegate) and 1989 (Merredin). At Merredin, 3 t/ha of limestone increas
ed grain yields in all years except 1982 and 1983. At Wongan Hills, li
mestone increased yields in the continuous cropping system, in the pre
sence of high N + P, during 1986 and 1989. At Newdegate, grain yield r
esponses to lime were recorded in 1980, 1981, 1982, 1986, 1988, and 19
89; limestone resulted in decreased wheat yields in 1984 because of an
increase in the severity of the root disease take-all (caused by Gaeu
mannomyces graminis var. tritici), and decreased lupin yields in 1987
because of manganese deficiency. There were a few responses at Merredi
n and Newdegate to low rates of limestone with each N + P application.
Application of the magnesium (Mg) + potassium (K) + molybdenum (Mo) i
n addition to limestone gave isolated responses at all sites. Concentr
ations of calcium (Ca), Mg, and K at the 1989 plant sampling were high
est at Wongan Hills and lowest at Merredin. Calcium concentrations wer
e higher at Merredin and Newdegate following N + P application, but lo
wer at Wongan Hills. Application of N + P reduced the concentration of
Mg at Merredin and Wongan Hills, but increased Mg at Newdegate. The c
oncentration of K was decreased at all sites by N + P. Limestone had n
o consistent effect on Ca concentrations but increased the concentrati
ons of Mg and K at Merredin and K at Newdegate. Where Mg + K + Mo had
been applied in 1980, concentrations of Ca decreased and K increased,
while there was no consistent effect on Mg concentration. The Mo conce
ntration in plant shoots was reduced at all sites by increasing rate o
f N + P and increased by application of lime and Mo in 1980. Grain Mo
concentrations were very low at Merredin and Wongan Hills, even in the
absence of N + P. Concentrations at Newdegate were reduced by increas
ing N + P rate. Application of limestone increased grain Mo concentrat
ions at all sites, but these were still lowered by N + P application.
Concentrations were also increased by the application of Mo in 1980, b
ut fell with time, particularly with application of N + P.