Neighobouring properties are 1 of the biggest problems with going organic in general.
They spray on windy days & we can cope it & if soil is tested & chemicals found we will be fined, not to mention to whole idea of choose.
They let weed get out of hand as for them a load of chemicals & a few hours labour has it fixed. But when doing it without chemicals it can take a few days & hard work to clear a weedy patch caused by seed coming on the wind & wing from the next property.
What grass/pasture do you have?
Some are better at out competing the weeds then others.