At the block level Leaching-other is the leaching from the inter-urine patch areas. It incorporates the effects of soil fertiliser, effluent and other nutrient input sources. Leaching - other is reported in the Nutrient Budget under Leached from root zone. This can be particularly affected by the level of inorganic N in the soil and the level of drainage occurring in the block.
The higher the level of inorganic N, and the higher the drainage - the higher the Leaching-other will be.
On pastoral blocks, in most cases, leaching from the inter-urine/background model is less than that from the urine patch model because pasture is efficient at removing N. The exception is usually associated with high inputs of N such as fertiliser or effluent and in those cases, N 'leaching-other' can be mitigated by reducing N inputs.
However, 'leaching-other' can be particularly affected by the level of inorganic N in the soil, the level of drainage occurring in the block and soil type through Profile Available Water (PAW).
- Soil inorganic N depends on many inputs: block characteristics (e.g. slope), crop uptake, fertiliser applications, rate of mineralisation etc. In the model, a proportion of the soil inorganic N pool is assumed to leach each month.
- Drainage depends on climate and soil characteristics.
- PAW is soil specific
The higher the level of inorganic N, the higher the drainage, and the lower the PAW - the higher the Leaching-other will be. In these situations, where N inputs are low, there are limited options to mitigate leaching-other losses. One option is to increase stocking rate. OverseerFM subtracts the energy gained from eating supplements from the energy required by the animals (based on age, sex, weight, production etc.) to determine the amount of pasture eaten and hence pasture grown. Therefore, the more animals on a block, the greater the pasture intake and hence pasture grown. The more pasture grown, the greater the crop uptake which reduces soil inorganic N (N available to be leached).
On grazed cropping blocks, the amount of N leaching-other can be influenced by fertiliser rate and timing, effluent rate and timing, cultivation timing and method, crop yield, and harvesting of the crops.
In the farm level nutrient budget, leaching - other is the area-weighted average background losses from the blocks, plus losses from lanes, unlined standoff pads, effluent storage system, wintering pads and silage stacks. Some of this loss may occur as runoff, particularly for P, but there was insufficient information to split between runoff and leaching when the model was developed.