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Prediction of lucerne responses to lime from soil tests

G.P. Mahoney1, J.M. Hunter1 and H.R. Jones2

1 Department of Agriculture, District Office, Benalla 3673
Department of Agriculture, District Office, Bendigo 3550

The requirements of lucerne for lime are often not able to be satisfactorily predicted from soil pH (Jones 1975). Kamprath (1970) has suggested that benefits from lime on acid soils accrue from neutralization of toxic minerals rather than pH. Thus level of selected minerals in soil may be useful as a predictor of lucerne response to lime on such soils.

Various amounts of ground limestone were broadcast on acid granite soils at Gooram and Strathbogie at the time of establishment o-f Hunter River lucerne in 1972. The amounts were 0.6, l.3, 3.5, 5 and 10 t ha of limestone (44.8% calcium oxide). The relation between production of lucerne over 4 cuts in its second year of establishment and soil tests of exchangeable aluminium (Al), available manganese (Mn) and pH in the topsoil and subsoil was examined for each site (Table l). The stepwise model operating for retention of significant (P < 0.05) coefficients was of the following form :

Y = a + bA1 + cA2 + dM1 + eM3 + fPl + gP3.

where Y = lucerne yield t ha-1, Al, Ml, and P1 were the levels of exchangeable A1 (ppm), available Mn (ppm) and pH respectively for the topsoil and A2, M2 and P3 were the corresponding values for the subsoil.

TABLE l: Selected analytical results

The following prediction equations were obtained:

Gooram site Y = 15.65 - 0.05 (0.03) A2 - 0.13 (0.03) M1... [100R3 = 83%]
Strathbogie site Y = 8.14 - 0.03 (0.01) Al - 0.40 (0.17) M1...[100R2 = 89%]
Combined sites Y = 14.0 - 0.03 (0.01) A1 - 0.03 (0.01) A2 - 0.11 (0.03) M1
... [100 R2 = 89%]. The standard errors of the coefficients are shown in parenthesis.

Yield responses were predicted accurately from the analysis of exchangeable aluminium in top and subsoil and available manganese in topsoil. This study extends the findings of Jones (1975) who found in glasshouse studies of several soils that the response of lucerne to lime was dependent on the aluminium status of the soil.

Kamprath (1970) Soil Sci. Soc. Amer. Proc., 34: 352.

Jones, H.R. (1975) M. Agr. Sc. Thesis, University of Melbourne.

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