Proper research would resolve BCSR debate
AS A farmer with an interest in soil management I am always looking for information to deepen my understanding of how to best look after the soil on my farm.
They cite overseas research showing sufficiency levels (ppm) are better predictors of crop responses than BCSR. Dr William Albrecht, emeritus professor of soils, Missouri State University, wrote at least 400 scientific papers, many published in leading scientific journals during his lifetime and compiled in the Albrecht Papers Volumes I-VIII.
Although Albrecht is noted for his balancing of calcium, magnesium, potassium and sodium ratios in the soil, he also studied nitrogen, phosphorous, sulphur and trace elements, looking at the bigger picture of how soil fertility impacted animal health and ultimately human health. He was an outspoken critic of the simplistic NPK approach to soil fertility. With his animal health focus, I believe many of his findings are relevant to our own pastoral agriculture.
Edmeades’ claims that his own research shows calcium:magnesium ratios do not affect legume production flies in the face of Andrew Carran’s research published in the NZ Grasslands Association Proceedings Vol 54 p.78 under the heading ‘Effects of Soil pH and Ca:Mg Ratio on Plant Growth’: “Under the condition of wide Ca:Mg, reliming appears to be harmful and depressions of growth of white clover after liming may occur. Substituting magnesium carbonate for calcium carbonate (lime) at equivalent rates; reduces and ultimately eliminates the depression of clover growth”.
Edmeades also claims plants do not need sodium. Not so, according to research by Dr Max Turner of Massey University, who found pasture responses to salt over 30 years ago – and also that the potassium:sodium ratio in pastures – were important for reducing ‘frothy’ bloat.
More recent research by Cambridge University scientists Dr Clive Phillips and Paul Chiy found the application of 100kg of salt to pastures gave milk production increases of up to 10%. The reasons for this they put largely down to increased consumption (palatability) and an increase of the water soluble carbohydrate (sugar) content in the grass. They suggest an optimum sodium level in pastures of 0.4% DM. Sugar beet crops have a particularly high requirement for sodium where applications of 150-200kg/ha of salt are common.
Edmeades’ other claim that there is no calcium deficiency in New Zealand soils I would also challenge. The marine clay soils of the Hauraki Plains and the Ruawai flats on the Kaipara Harbour, for example, have too close Ca:Mg ratios and will respond to lime even when soil pH is at the normal optimum for pasture.
On such soils gypsum (calcium sulphate) can be a better source of calcium because raising soil pH with lime too high can interfere with the availability of some trace minerals. On these soils the calcium has a flocculation effect on the tightly bound clay particles, and such pastures often have calcium levels too low for optimum dairy cow health and production, and pasture palatability problems can occur until soil and plant calcium levels are raised.
There are extreme soils where Albrecht’s optimum ratios are irrelevant. When consulting in England I came across calcareous (chalk) soils which had in excess of 90% calcium in their base saturation. Conversely, in parts of Australia and South Africa there are soils with extremely high magnesium ratios and to try and bring these into line with Albrecht optimums would be near impossible let alone prohibitively expensive.
In my view, BCSR is a valid tool in the tool-box for a soil consultant to work with – but certainly not the only one.
• Robin Boom is an independent soil consultant sending soil samples to Brookside Laboratories, Ohio, the original Albrecht lab, specialising in the complexities between soil, plant and animal health. email This email address is being protected from spambots. You need JavaScript enabled to view it.
