INOCULATION OF CLOVER SEED

Press, Volume CIII, Issue 30342, 18 January 1964, Page 6

INOCULATION OF CLOVER SEED

TpHERE is not enough evix dence to recommend inoculation of clover seed when sowing a new pasture on improved land that has been growing good pastures, says Professor T. W. Walker, professor of soil science at Lincoln College, in a recent bulletin issued by the Canterbury Chamber of Commerce. He says, however, that more experimental work is required. It costs so little to inoculate clover seed that it would be desirable to see some farmers experimenting with it. It is now known that there are many different strains of bacteria, some of which are considerably more efficient at fixing nitrogen than others. Professor Walker says that this is important because once a plant has become inoculated with an inefficient strain it is unlikely to become infected with a more efficient bacteria. Consequently some of the clovers in pastures may be' producing much less than they might. Use of pelleted seed on soils that have been limed is not recommended in the present state of knowledge, except for protecting the inoculant from direct contact with fertiliser. Discussing both the results of a plot trial with subterranean clover in a high country soil with a very low pH of 4.9. and a field trial with a mixture of clovers on a soil with a pH of 4.9 at the top of Lake Ohau, Professor Walker noted that pelleting of inoculated seed gave poorer results than no pelleting where the soil had been limed. The use of lime-reverted

superphosphate might do away with the need for pelleting the inoculated seed, he says.

There is enough evidence to suggest that unless soils have been limed so that the pH is between 6 and 6.5, inoculated lucerne is very likely to benefit from pelleting. The lucerne bacteria and the actual process of

nodulation of lucerne seem to be more sensitive to acidity than in the case of clovers. Referring to tussock country or any other land undergoing initial improvement, Professor Walker says that there is enough evidence now to suggest that inoculation of clover seed may greatly assist establishment on very acid soils. It would be a wise and cheap precaution to introduce highly effective nitrogen-flxing bacteria when first establishing clover on ibis country.

The need for inoculation may be less if time of sowing and climatic conditions are satisfactory—for instance, if the seed is sown early enough, say in July or August, there may be time for bacteria from natural sources to produce nodulation before dry conditions set in. Professor Walker says, however, that he would still prefer to inoculate the seed and minimise the risks.

The merits of pelleting are more difficult to assess in the present state of knowledge. If a farmer inoculates his own seed just before sowing, uses lime-reverted super and gives a light liming—say 10 cwt per acre—on very acid soils, there may be little advantage from pelleting. Tf he has not limed, if he wants to sow his seed with straight super or sulphurised super with or without molybdenum, or if he wants to store inoculated seed for some days before sowing, then pelleting would probably be beneficial. Current research on these problems will lead sooner or later to the cheapest possible methods of clover establishment—the first phase of pasture improvement “Finally,” says Professor Walker, “a well-nodulated clover plant will only thrive if all other factors, particularly nutritional, are corrected. It is no good fitting false teeth in a toothless tiger and then starving it of meat. A nodulated clover plant will only fix nitrogen if we correct all deficiencies of phosphate. sulphate, molybdate, potash or any other elements.”