Soil health<\/p>\n
\u201cI spent 11 years working in the land division of M\u0101ori Affairs, followed by 12 years supervising M\u0101ori Trusts in a private capacity,\u201d Petersen said.<\/p>\n
\u201cSince 2008, I have focused on enhancing soil fertility and economic viability for farmers and growers.\u201d<\/p>\n
Most farms followed the traditional NPK fertiliser system. <\/p>\n
Soil tests were routinely carried out, but there was little real expertise in interpreting individual results, so farmers tended to apply the same inputs year after year.<\/p>\n
\u201cThere was no one to discuss soil health with in those days,\u201d he said.<\/p>\n
\u201cDuring a course near Brisbane on soil fertility, lots of pennies dropped for me.\u201d<\/p>\n
During his time as a farm supervisor, Petersen explored products and methods from six different companies in order to identify the best options.<\/p>\n
\u201cCorrectly balancing the soil should be the goal of any soil fertility programme, and we need to move away from the more harmful products, which are often the cheapest.\u201d<\/p>\n
Kinsey Agricultural Services produced manuals showing how to calculate nutrient requirements from soil samples using specific formulae. <\/p>\n
These were based on the work of Dr William Albrecht, who authored more than 400 papers on soil fertility and developed the Albrecht System of Soil Fertility \u2013 an approach focused on feeding the soil and letting the soil feed the plants.<\/p>\n
These manuals and papers form the foundation of Petersen\u2019s soil management approach. <\/p>\n
High-quality crop yields tend to share similar soil chemistry: calcium at 60-70%, magnesium at 10-15%, potassium at 5%, sodium at 1.5%, with defined levels of nitrogen, phosphate, sulphur and trace elements.<\/p>\n
Ripening bananas and a banana flower. Photo \/ Catherine Fry<\/p>\n
\u201cThe Lincoln University Dairy Farm [LUDF] achieved a best return on investment [ROI] of 4.5%,\u201d he said.<\/p>\n
\u201cOn one of the M\u0101ori Trust properties I supervised, our worst ROI was 4.6%, and our average was 8.5%, using only 10% of the nitrogen applied at LUDF.\u201d<\/p>\n
Tending land<\/p>\n
In 1980, Petersen purchased 4ha on Ohakana Island in \u014chiwa Harbour, where he built a home and grew tamarillos and passionfruit, quickly gaining organic certification for the land.<\/p>\n