Lime and manganese cocktail? Yes, for increased yields


Higher yields and better soils are the payoff after only a few years of applying lime with added nutrients in trials run by the Liebe Group on sandplain soils near Buntine, 250 km north of Perth in Western Australia.

Supported by growers and the Federal Government through the GRDC and by Agriculture WA, the trials were set up on Kim Diamond's property, 'Guyscliffe', in response to grower concern about occasional negative responses of lupin yields to liming.

"We've always seen a positive response to liming in our other crops and pastures. It was obviously more than just a simple matter of getting the pH right for lupins. We also needed to know the nutrient balances," says Mr Diamond.

Trials start 1996

Three rates of lime - 0, 1 and 2 t/ha - were spread onto two sets of plots at the start ot the trials in 1996. Potassium (topdressed at 100 kg/ha in 1996) and manganese (as 6 L/ha Mangasol) were also applied after some tests revealed the possibility of lime-induced manganese deficiency.

It was the immediate increase in lupin yields, from 0.8 t/ha to 1.01 t/ha in all plots treated with potassium and manganese, that most caught growers' attention.

"No-one expected the difference to be so clear-cut. We now routinely treat lupin seed with Mangasol prior to sowing," says Mr Diamond.

Although tissue testing earlier in the season had shown both potassium and manganese to be low on at least one of the sites, a statistical analysis showed that it was adding manganese that had the most impact on lupin yields. Neither nutrient had any effect on wheat yields.

As expected, soils with lime applied showed an immediate improvement in pH in the surface 5 cm in the first year (1996), increasing from around pH 4.8-5.3 to pH 6.5 (for 2 t/ha lime). Increases in subsoil pH were seen after three seasons, in 1998. At that point wheat grain protein levels also increased from 9.87 per cent to 10.30 per cent (2 t/ha lime). Yields for wheat and canola started increasing in the 1999 season.

"Although we have been liming since the 1960s, we really had only anecdotal evidence that we were improving the soils, and yield increases were sometimes a bit hard to see because they took a few years to come through," says Mr Diamond.

The yield differences in the 1999 season were an impressive extra 0.25 t/ha of canola and an extra 0.2 t/ha of wheat, both after 1 t/ha of lime in 1996. Two tonnes of lime (applied in 1996) increased wheat yields in 1999 by nearly 0.4 t/ha (shown in Table 2).

"By 1999 we could see the difference in growth between the plots during the season, and by the time we harvested we could easily see from the colour which plots had been limed and which hadn't," says Mr Diamond.

There was no effect of any of the treatments on the oil content of the canola grain in this trial.

An economic analysis on one set of plots by researcher Chris Gazey showed that the average gross margin for each of the four years of the trial was $8/ha/yr for the 1 t/ha liming rate, and $17/ha/yr for the 2 t/ha liming rate. The gross margin was smaller, but still mostly positive, for the second set of plots due to a poor response by canola to heavier rates of liming.

"There must be some other factor limiting canola yields on those plots, preventing a full response to lime," says Mr Gazey. "It does emphasise that we need to be looking at the farming system as a whole."

Mr Diamond has said that he is now more cautious about what he does and where.

"We could be adding around 4 t/ha lime every five years or so but we're a bit nervous about what that could do to the plant nutrition. At $22/ha for lime, including freight and spreading, it's certainly not the costs that are stopping us."

Table 1. Agronomic information for one set of plots in Liebe Group liming trials at Guyscliffe'. A second set of plots was managed in the same way, but a different rotation was used (wheat-lupins-wheat-canola).
RotationLupins (Merrit)Wheat (Eradu)Canola (Karoo)Wheat (Brookton)
Sowing Date7/5/96Late May12/5/9828/5/99
Sowing Rate100 kg/ha70 kg/ha10 kg/ha73 kg/ha
Sowing MethodMin tillMin tillNo till (Great Plains)Min till
FertiliserS = 80 kg/ha SuperPS = 64 kg/ha urea
S = 75 kg/ha Agflow
PS = 113kg/ha
Agras No.1**
PO = 80 kg/ha urea
S = 72 kg/ha Agflow*
60 kg/ha urea
PO = 55 kg/ha urea
HerbicidesPS = 2 L/ha Simazine,
0.5 L/ha Roundup + wetter
P0 = 75g/ha Metribuzin 300 mL/ha Correct in June
50 mL/ha Brodal in July
PO = 1 l/ha Hoegrass,
0.5 l/ha Tigrex
PS = 2L Atrazine
PO = 2L Atrazine + 2% oil, 100ml Lemat
PO = 220miTarga + 1% supercharge,
100ml Dimethoate
PS = 11 Roundup
PO = 0.5 l/ha Tigrex 10g Logran

* Agflow fertiliser is 13.2% N, 17.8% P, 6.6% S and .02% Zn.
** Agras No 1 fertiliser is 17.5% N, 8% P and 17% S, with a trace
S = applied at sowing, PS = applied pre-sowing, PO = applied post-sowing

Table 2. Grain yields of wheat and canola in 1999, after applying various rates of lime in 19%.
Time rate applied in 19961999 canola grain yield1999 wheat grain yield
0 t/ha0.74 t/ha3.47 t/ha
1 t/ha0.99 t/ha3.67 t/ha
2 t/ha0.86 t/ha3.86 t/ha

Program 3.4.3 Contact: Mr Chris Gazey 08 9690 2149

Region North, South, West