Every year filling in the manure balance forms a problem. By using the assumptions and the use of analysis, errors can slip in the balance sheet that can't be ignored. Next to the genetic evolution of the animals, the errors lead to an imbalance in the balance. VLM says the imbalance suggests an incorrect manner of disposal of the manure or a too big amount of received manure by the farm, so it will be fined. BFA, backed up by ABS and Boerenbond, suggests the error isn't always with the farmer and there is more going on than VLM thinks. That's why this three headed group has committed to provide more clarity to this issue.
In agreement with VLM, it was decided to set up 2 experiments to prove that the used methods to gain input data isn't up to date anymore. BFA suggested to use new simulations for the regression line (for finishers and sows). The newly simulated regression lines, used to set up the nutrient balance, were approved by VLM. To set up the simulation of the regression lines, it was mainly the feed conversion and growth of finishers that was adapted. Also the excretion data for low nutrient feed was adapted.
The first experiment was executed March 2013. This experiment, the so-called extended ringtest, needs to bring clarity about the error for manure analysis, the error for sampling and the diversity between the different approved labs. Theses results were processed by an independent research centre and made public to the organizing parties at the end of May 2013. More information about this below.
A second test investigated the retention value of N and P in pigs. It's been suspected that the P-excretion of pigs is lower than what is theoretically assumed. The higher P-retention in pigs would be caused by the genetic evolution which affects the growth and meat percentage, etc. The research centre, ILVO, has some experience in setting up and carry out this kind of experiments and so carried out a retention experiment using 72 pigs. The results showed no difference in retention values for N and P. This project was supported by ABS, Boerenbond, BFA and VLM.
This shows that the error on the analysis from N is very small. The method of taking the sample doesn't have a big effect on the analysis. This is because N is homogeneously dispersed in the manure. The error from P and dry matter is too high to be acceptable. The test shows that there is little point in analyzing P, because the range in results is too big. The way of sampling has a very big effect on it. When the sampling happens on a lot of thick fraction, the value of P will be high in the sample. However, when the sampling happens on thin fraction, the value of P will be low.
The reason of bad sampling is partly caused by the person who takes the samples, but more than 75% is caused by stable conditions. The shed construction in those 7 companies didn't allow correct sampling. The procedure described to take a sample isn't possible in reality. An alternative was needed.
During the years 2014-2017 a solution was sought. Next system resulted out of this. Companies can chose out of 2 systems to determine the nutrient composition per sort of manure and exploitation:
1) General forfeit
2) Analyzing system (with the possibility to expand to company-specific manure composition)
At the start of every year, the farmer chooses which system he will use. The general forfeit (Table) for piggery's is based on median nutrient composition of the pig's manure.
Table. General forfeit values for pig manure
If the farmer chooses the analyzing system, he is obliged to take samples of the cargo. The mean composition of at least 2 cargo samples replaces the mix sample. The results of analysis are 3 months valid. Each sample needs to be reported through the 'Staalname Melding internet Loket' (SMIL). Through the analyzing system can be shifted to company specific manure composition. This is only possible if the spread between the cargo samples isn't too big. If the requirements are met, then the company specific manure composition is calculated as the mean of all the cargo samples for either N and P2O5. Als toetsing in de toekomst zal voor N de vork 0.75 kg gebruikt worden, en voor P 1.0 kg.