Waikato-based Soil Scientist Gordon Rajendram PhD is considered one of New Zealand’s experts in soil fertility. He is committed to helping New Zealand farmers get the most out of their soil so that their farm can work more proficiently, be sustainable while still increasing farm profitability. Dr. Gordon Rajendram worked at AgResearch, Ruakura Research Centre, Hamilton. He has developed two field calibrated soil tests (N & S) which are used for agronomic advice in NZ and his work on leaching has been included in the Overseer nutrient model.
There are many aspects to consider for healthy soil and pasture production. The appropriate soil testing can help you get it correct says Hamilton-based Independent Fertiliser Consultant and Soil Scientist Dr Gordon Rajendram PhD.
There are two key factors that drive pasture production. Firstly, there is soil temperature measured at 10 cm. At 5 or 6 degrees, pasture stops growing. Second is soil moisture. With a soil moisture <25 % there can be significant impact on pasture production. ‘Using a Field Calibrated Soil Test will help the farmer identify if they are achieving maximum pasture production, low productivity or wasting money due to excessive use of a nutrient,” says Independent Fertiliser Consultant and Soil Scientist Dr. Gordon Rajendram PhD.
In addition, pasture species struggle on low pH soils due to the increased Aluminium in the soil solution which retards root growth, resulting in less growth of herbage. New Zealand farmers are not applying lime particularly on hill country, so many soils are getting very acidic (< 5.5 pH), with soils getting down to as low as 5.0 pH. However, with right testing and planning there is room in every budget for both lime and fertiliser to reduce soil acidification.
Leaching is the loss of water-soluble plant nutrients from the soil, due to such factors such as rainfall and irrigation. “Amount of nutrient lost via subsurface flow is related to amount of rainfall and drainage,” says Gordon.
Plant essential nutrients exist as anions and cations, and the leaching of these anions and cations is conditional on various factors including the amounts and form of nutrients applied in fertiliser, stocking rate, drainage, soil type and extent of previous leaching.
Anion Storage Capacity (ASC) or Phosphate retention (P-retention) is a measure of the soil to remove P from soil solution. “This is key test which is inherent of the soil type should be included with every sampled area to determine its level. This is exceptionally valuable information when bearing in mind the use of phosphorus and sulphur fertilisers,” adds Gordon. Research shows that 70% of sulphur applied in a soluble form is leached from NZ soils.
Phosphate is a key element for plant growth. Any phosphate applied needs to stay in the soil and not runoff as particulate P or leach into subsoils. Much of the loss is related to the soil type, climate, Anion storage capacity, and overuse of soluble forms of P.
Mitigating P losses
- < 40% ASC greater potential to lose P from soil
- Apply little bit often
- Important to use right product
- Apply slow-release P & S products
- Combo of water soluble/slow-release P & S is best
it is important to remember that fertiliser itself is only one aspect of a productive fertiliser management system. “If you don’t test and do it properly you are doing a disservice to your business,” adds Gordon. Ensuring that it is applied at the right time, place and rate is equally important.
About The Soil Scientist
Gordon is a Independent Fertiliser Consultant and is dedicated to helping all farmers get most out of their soil so that their farm can work more efficiently, be sustainable while improving the farm profitability.
Phone: 021 466 077
Phone: 0274 587 724