Hello, Community! Hope everyone is well!
We know that load_p or load_n indicates the average annual load of phosphorus or nitrogen on each land use type. So this value should be related to the study area and the socio-economic development characteristics of the study area in different periods.
However, when there is a lack of statistical data related to nitrogen and phosphorus emissions in the study area, and also, no scholars have previously studied the emissions or loads of nitrogen and phosphorus in the area.
I would like to ask, when nitrogen and phosphorus load data are lacking, can the nitrogen and phosphorus load values refer to the research results of other surrounding regions? This must have a significant impact on the assessment results, right? (Or the result will not be very reliable)
Or, is there any other solution? 
Thanks a lot！！！
Hi @littlepencil -
It is often (really, usually) the case that we do not have loading/efficiency information specific to the area we’re working in. Or, sometimes we’ll have loading information for one or two land cover types but not others. So it is common to use values from other places. If you have data from surrounding regions with similar land cover types and/or land use practices, that’s great. If not, then we might find more general values from similar places elsewhere in the country, region, or world, or even global average values, if that’s all we have. The goal is to find the best that’s available, and that’s different in different places and contexts.
Yes, the choice of loading and efficiency has a big impact on results. I’d say that the most important thing is to get the relative values correct, so you feel confident that, say, this type of agriculture uses more nitrogen than another one. Then the patterns of results will be useful. It’s perhaps more important to get the individual loading values correct if you’re really relying on the absolute values output by the model, in which case you’ll be doing calibration and validation and adjusting inputs anyway. You can also do a sensitivity analysis to see if/how much the values and patterns change when you input a range of loading values. That way you’ll know which parameter(s) it’s most important to get local data for. And if the patterns are very similar regardless of which loading values you choose, you can feel more confident about the results.
~ Stacie
Thanks, got it. In the case of incomplete and inaccurate parameters or data, it is feasible to use the relative values of the assessment results for the study.