Quick Dips

Soil Infertility

Dung and urine patches are the only things holding total soil infertility at bay on many Southland pastures, according to AgResearch scientist Dr Rex Dolby. Many pastures are domin-ated by grasses, weeds and moss in conditions reminiscent of the low fertility of the 1950s.

"In paddocks where pasture in the dung patches is doing well, phosphate and/or nitrogen is deficient," notes Dolby. "And urine patches in paddocks indicate sulphur, potassium, and/or nitrogen deficiency."

A lack of high fertility grasses and no nitrogen-fixing nodules on undersized clover plants shows major soil deficiencies, particularly in nitrogen and molybdenum. Farmers have been cautious about applying molybdate, concerned about possible copper deficiencies caused by molybdenum binding copper. In some cases, the molybdenum drop reflects a reduction in general fertiliser applications.

Dr Dolby hopes to encourage farmers to test pasture as well as soil before deciding on fertiliser regimes, to accurately assess deficiencies.