August 28, 2002

Soils developed on the Dandaragan plateau’s sandstone have some of the most marginal soil boron (B) levels of WA’s sandy, acid soils.

B deficiency can decrease canola and lupin seed yield as they are more sensitive to B deficiency than cereals. This has been prevalent in pot trials growing seeds in sandy, acid soils from the west Moora-Dandaragan area.

Research, supported by graingrowers and the Federal Government through the Grains Research & Development Corporation investigated the spatial distribution of B deficiency in canola and lupin and determined the role it plays in grain yield for these crops.

Murdoch University’s Associate Professor Richard Bell and Kirsten Frost, CSIRO’s Dr Mike Wong, Western Autralia Department of Agriculture’s Ross Brennan and CSBP futurefarm’s Dr Stephen Loss sampled young canola and lupin leaves and soil for B levels at more than 150 sites throughout the wheatbelt, mainly on sandy soils, with 10-20 per cent of sites potentially B deficient.

Additionally, 73 reference soils from WA’s south west were analysed for hot calcium chloride (CaCl2) extractable B and then correlated with soil pH, clay and sand. Extractable soil B tests showed that low clay content, below 10 per cent, and a low pH, below five in CaCl2 , could help predict low soil B.

Eight reference soils were used in canola and lupin pot trials, grown with and without added B and measured at maturity for seed yield. Fertiliser B increased growth and seed set in canola on four low B soils, but in lupins it only increased pod set on one soil type. Decreased seed viability of lupin was expected when seed B was less than 12 mg/kg and particularly at less than 6 mg/kg.

Foliar and soil B applications used in 14 field trials in the 2000 and 2001 cropping seasons resulted in no seed yield increases in either lupin or canola. Canola yields were all very low in 2000 due to low rainfall, but the following year, when canola yields were higher there were still no positive responses to foliar or soil applied B fertiliser.

Although the study showed risk of B deficiency, it was not severe in any areas studied.

While B fertiliser was not required, growers should continue to monitor crops for B deficiency symptoms, particularly in canola, lupin and chickpea, and also in sensitive pastures like lucerne.

Lupin was particularly sensitive to damage if more than 5kg borax/ha was applied at sowing, so growers should consult an agronomist on appropriate rates before applying boron in the field.

The Crop Doctor is GRDC Managing Director, Professor John Lovett, Tel 02 6272 5525

Further Information: Associate Professor Richard Bell, Tel 08 9360 2370