At the Marlborough Beef + Lamb New Zealand field day in November Lachie Grant, of LandVision, said it was worthwhile putting paddocks together into land-management units and farming according to their potential.
Field-day participants mixed water with soil to test clay content. A sticky soil means a higher clay content and a propensity for pugging. A smoother feel means more silt than sand.
The flats at Kaituna Ridges were split into four main types. Suzie highlighted the difference between alluvial soils (recent soils developed on material deposited by the waterways) and colluvial soils (brown soils from material that has slid from hills). For this property the alluvial flats are more free-draining, with lower organic matter content. They had potential to grow 12 tonnes of drymatter (t DM) and stock 13.7su/ha, she said, but low water-holding capacity meant it dried out quickly.
“It has lower natural fertility but responds quickly to fertiliser.”
Colluvial soils hold their moisture better, making them versatile and good for summer production. The typically can graze stock for longer in summer (14.1su/ha) but Suzie estimated that these soils at Kaituna Ridges would grow slightly less than alluvial (around 10 to 12t DM). They were typically acidic and had low to medium retention of phosphate.
“Fewer nutrients are likely to be plant available.”
Suzie suggested that after 14 years of Reactive Phosphate Rock a more available form of phosphate might be a good option for the flats. Before choosing a fertiliser, the cost of a kilo of nutrients should be calculated.
Likewise the hill area was split into three main land-management units. Hill-country options included applying more sulphur for clover. Phosphate might be at its economic optimum, at 17, Suzie said. Erosion risk was minimal, but they needed to be wary of leaving too much drymatter on the hills as the weight of it when wet could cause slips. There was a fine line between over-grazing and under-grazing.