Median and weighted mean yield ratios for field & forage crops (Manuscript Fig 1).

Dry edible bean production data by state

The median yield ratio for dry edible bean was 0.62, substantially less than the weighted mean yield ratio of 0.74. Of the 11 states where both organic and conventional dry edible bean were grown in 2014, only 3 reported organic yields greater than conventional yield (Table 2). Arizona had the greatest organic dry edible bean area (35% of the total) and also had the greatest yield ratio (1.38). The top four states for conventional dry bean area (Michigan, North Dakota, Minnesota, and Nebraska) had much lower organic yield compared to conventional (average weighted yield ratio of 0.67).

It is unclear why such a difference between states was observed with organic to conventional yield ratio in dry edible bean. Since it is a legume, nitrogen deficiency should play a minimal role in contrast to many other organic crops, as long as the seed is inoculated with the appropriate rhizobium species. Idaho and Colorado represent relatively similar growing environments with respect to dry edible bean production, and conventional yields were similar between these two states (Table 2). Even though conventional yields were similar, organic to conventional yield ratios of 1.11 and 0.45, were observed in Idaho and Colorado, respectively, because organic dry bean yield was much lower in Colorado. Regardless of the reason for the difference, these results suggest that dry edible bean has potential to be grown under organic management practices without sacrificing yield, but that potential is not being met in most organic production areas.

Barley production data by state

The median yield ratio for barley was substantially less than the weighted mean yield ratio (Table Xbarley). Of the 18 states reporting both conventional and organic barley yield, only 2 (Washington and Oregon) had a yield ratio greater than 1. In general, the states with the most organic farms reporting had yield ratios closer to 1 compared to states with fewer organic farms. The most notable exception to this trend was Idaho. Idaho had the largest area devoted to organic barley production (5105 hectares) and the greatest number of organic barley farmers responding to the survey (46), yet had among the lowest yield ratios, with organic barley yielding 52% of conventional barley. Idaho was the second leading producer of conventional barley in terms of area in 2014, producing over 200,000 hectares.

Haylage production data by state

Of the 15 states reporting both organic and conventional haylage yields, all reported greater organic haylage yields compared to conventional (Table Xhay). The organic to conventional haylage yield ratios ranged from 1.4 to 3.7. States with the greatest number of organic farms and organic area tended to have lower yield ratios, which resulted in a weighted mean substantially less than the median yield ratio for haylage (Fig 1).

Median and weighted mean yield ratios for fruit & vegetable crops (Manuscript Fig 2).

Peach production data by state

Median peach yield ratio was greater than 1, while the weighted mean was less than 1. The difference between the median and mean for the peach yield data was influenced by many states with very few organic acres in production (Table 3). Four of the seven states reporting both organic and conventional peach yield data had yield ratios greater than 1, but these states produced relatively few organic hectares (and had relatively few organic farms). Arkansas, for example, had a yield ratio of 6.0, but only 3 organic farms producing a total of 1 organic hectare. Georgia, the state with the second highest area of conventional peach production, had less than 1 organic hectare represented in the comparison. Washington and California, the two states with the largest number of organic farms and area, had yield ratios of 1.97 and 0.55, respectively. We were unable to find an explanation for the large difference between the yield ratios from Washington and California. It may relate to the ratio of processing to fresh market production in each state, and within each system within a state, since production issues like early frost and pest management can be less problematic for processing than for the fresh market.

Apple production data by state

The median yield ratio for apple was much lower than the weighted mean (Fig 2). The median was influenced by a large number of states with less than 10 hectares of organic apples that had organic yields less than 20% of conventional (Table Xapple). The two states with the greatest organic production both in terms of farms and area (California and Washington) had organic yield that was 81% and 78% of conventional, respectively, compared to the weighted mean of 60% of conventional for all states reporting both conventional and organic apple production.

Potato production data by state

Potato may be among the most difficult crops to grow organically relative to conventional. Organic potato yield was only 38% of conventional potato yield in our analysis, and the median was even lower, at 26% of conventional yield (Fig 2). None of the 20 states in our analysis reported organic yields greater than conventional, and only one state (Washington) reported organic potato yield more than 80% of conventional (Table Xpotato).

Grape production data by state

Of the seven states that reported both organic and conventional grape yields, none had yield ratios greater than 1. The grape yield ratio may be skewed somewhat in California (the largest grape producer for both organic and conventional) because organic wine grapes are often produced in low yielding coastal areas, while the conventional data includes the higher yielding Central Valley of California.