The purpose of the Excreta nitrogen (N) report is to present estimated monthly excreta N deposited (kg N/month) for each animal enterprise present on the farm.
Excreta N is estimated as animal N intake from pasture, supplements, and crops, less N in products (this includes live weight). Excreta N as urine and dung is then distributed around the farm, allowing for excreta deposited on blocks, the farm dairy, pads and lanes. Excreta deposited on the farm dairy and pads is distributed by the effluent management system.
In OverseerFM, the largest source of N leaching from pastoral farms is from the urine patch. The proportion of excreta N that is excreted, as urine is dependent on the diet N concentration, and is typically between 65 and 80% of total N excreted (Ledgard et al., 2003). The amount of N leaching from urine patches is based on urine N deposited on blocks, and the monthly risk of that urine leaching.
Table 1 - Monthly Requirements and Intake - Excreta N
The farm example above is showing 13,000kgN for the month of September deposited by the Dairy enterprise. When there are multiple enterprises on the farm, this report shows how much modelled Excreta N is coming from each enterprise.
Changes in Excreta N often broadly reflects the pattern observed for ME requirements and DM intake. However, the amount of N excreted may change as the diet changes, depending on the amount and composition (high N or low N) of supplements in the diet.