The gross value of agricultural production in Marin reached $84 million last year, its highest level ever and about $4 million more than in 2012, according to the county’s crop report released on Tuesday. Milk, which is the biggest commodity and accounts for 40 percent of the gross value, decreased slightly in both production and value in 2013. But according to Stacy Carlsen, the agricultural commissioner, “We’re on an up-swing [for the past few years], so a 2 percent loss in one year, $700,000, is not significant, especially when you look at the trend, when overall we’re going up.” The report also showed a jump in the number of acres used for fruit and vegetable row crops—up to 906 acres in 2013, from 330 in 2012. The value of those crops also shot up, from around $2.5 to $4.4 million. Mr. Carlsen said that was likely due to a mixture of genuine increases in farming mixed with better reporting that captured the true acreage. The number of acres under organic management—mostly pasture—also spiked, going from 33,427 acres in 2012 to 40,632 in 2013. Organics accounted for close to $46 million of the total gross value of agriculture—a 66 percent increase from the year before.