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Wise Utilisation of Nitrogen

November 13, 2008

By Raymond Burr © 2008

Fully sustainable economical and environmental agricultural food production systems can be established. However the biggest hurdle in establishing sustainable systems is the culture that farmers presently obtain information from. It is common practise to set a specific production target and then throw all manner of inputs i.e. Nitrogen plus its associated inhibitors, maize silage, multi mineral dispensers, drenches etc to try to obtain that specific production target.

Under Qlab's production system construction, we start at ground level. In order to achieve sustainability, first components of your farming system must come first (that's logical). It starts at soil level. At Qlabs we treat all essential elements with equal importance, as they all have an effect on your systems ability to produce a profit. How our approach to soil fertility differs from the current main stream approach is quite simple, although complex in approach to achieving high fertility soils. The commonly used Quantity Theory of fertiliser application applies N (nitrogen), P (phosphorus), K (potassium) and S (sulphur) in abundant supply for maximum grass growth, with the application of Lime to adjust the pH of the soil. 

Qlab's approach uses the ratio theory of fertiliser application. Once a soil has been tested at our lab, a recommendation is given. This adjusts levels of the essential nutrients, S (sulphur), P (phosphorus), Ca (calcium), Mg (magnesium), K (potassium), B (boron), Fe (iron) Mn (manganese) Cu (copper) Zn (zinc) Co (cobalt), to raise the plant available nutrients in the soil up to optimum levels. As the soil fertility increases the optimum soil pH will be achieved. Our approach to Nitrogen is in our understanding of the relationship between the carbon cycle and the nitrogen cycle. If we fertilise our soils using the Ratio Theory, as the soil health and fertility increases the carbon cycle will increase. Nitrogen makes up to 78% of the atmosphere and a healthy soil should contain 50% soil, 25% moisture and 25% air space. As you can see the 25% air space in the soil, at 78% nitrogen, is a huge source of free N in abundant supply that is available once tapped!! 

It is commonly accepted that every 1 kg of fertiliser N used on average will reduce clover fixation by about 0.5kg of N. At the current prices of N fertilisers the actual cost per/kg/DM grown using applied fertiliser N is in actual fact a lot higher, given the fact that 0.5kg of free N is lost. So multiply the cost of N by 1.5 to give an actual cost, you can do the maths. In suggesting that the N in the soil is free may be misleading unless a short explanation is given. At this point the complexities of the interaction of the carbon cycle and the nitrogen cycle may be touched on. The free N is converted to plant available N by the biological activity within the soil. This biological activity is part of the Nitrogen cycle and the Carbon cycle (Synergistic relationship). As previously stated, Quantum's approach is to increase the carbon cycle by applying fertiliser, as the carbon cycle increases the free 78% of N from the atmosphere i.e. the air we breathe, is tapped into and utilised at a higher rate. The cost of achieving this is your fertiliser budget. Using this approach there will be little to no surplus N within a production system that can be leached through the soil or allowed to run off into waterways. The leaching and run off of fertiliser N is not only damaging to our waterways it is also a monetary loss from your cash flow. 

There are many benefits through using the Qlabs approach that may not always be visually obvious within a production system but will have a positive input on profitability through improved pasture persistence, animal health etc. Many of our clients comment on the unbelievable animal health benefits that they have obtained in a very short space of time. All expenditure that can be done away with is a return to the farmer as profit. 

Another effect of a well constructed, high fertility soil is the ability to grow high performing pasture species. For several years now the dairy industry has been pushing very hard for a longer, flatter milk production curve. At the same time meat industries schedule payments per kg of meat that reward those that can produce out of season prime animals. It's almost ironic that there are several pasture species known to us that have the ability to produce very flat production curves of high kg/DM/Ha and high energy. Under the right conditions these pastures are capable of producing in excess of 20 tonnes of DM/Ha/year with no requirement for fertiliser N. These pastures are of the highest quality and quantity producers and to no surprise will only persist in high fertility soils. Trying to establish these pastures into your production system with anything less than their required plant available nutrient status is a certain recipe for failure. Pasture based production systems will always remain the backbone of Agriculture in New Zealand. Qlabs' approach is one of Co-ordinated Soil>Plant>Animal Nutrition.