I just dug up the first bed of potatoes. While not quite the yield I wanted, it is very close and actually very good considering.
A raised bed, 45 sq ft, planted with 48 potato starts, a mix of yukon gold and yukon gem ( and actually, one start turned out to be a russet) . The yield, 39 pounds : 28.25 of yukon gold; 1/2 pnd baby russets; 6 pounds yukon gem; 4 pounds dug up last month as early potatoes. How to Grow More Vegetables "minimum" yield on their chart would be 45pounds for 45 sq ft. US average potato yield per square foot would be 1/2 pound per sq ft -- so this bed, at 3/4 pound/sq ft, came in right in between US commercial average and low end "ideal" biointensive yield.
They plant more densely at 9 inch centers, mine were close to 12 inch on center - so I planted less plants ; they have a certain amount of assumed compost and fertility to the beds, and beds double dug - I loosened the soil and just planted, intending to go back and mulch with the high fertility goat stall cleanings, but I never did ( I have alot of health problems, things dont get done ideally alot) . The bed grew bigger better butternut squash last season.
The lack of the goat stall cleanings was evident, the soil by the time I harvested was very low on organic matter, and the soil varied across the bed due to the high sun load here on a non-mulched bed. Some areas were quite compacted and dry, while the end of the bed by the black walnut sapling ( a weed) was a bit too wet.
Besides the location in the bed effecting plant yield, the difference between the yukon gold and yukon gem was dramatic. yukon gold is a little bit earlier, so it was done before conditions here got bad. I live at 2400ft, the weather can be erratic. A couple weeks ago, we had almost 2 weeks of a heat wave, many days over 100 degrees, and often not cooling at night. This past week, it has got down to teh low 40s at night with moderate days.
Some yukon gold plants had 1.5 pounds of potatoes per plant, quite a few yukon gem plants had a few ounces. So, while I aim for at least 1 pound per plant on average, I actually averaged more than 3/4 pound per plant --- 285 kcalories per square foot --- . Given all the detrimental conditions, I am very happy with this. If the growing had to be done "for real" in a changing world, I would have help and fertility/mulch/water would be done in the more ideal way and yields would be better. My skills I am developing would be of some use, even if I cannot physically do it.
There are 2 more beds of potatoes, the next one will be done in a few weeks, and the third may need a shade cloth as it went in late ( my dd came on spring break and built that bed, it is new and only less than 40 sq ft)
I will ( hopefully) be experimenting with fall grown potatoes too, so some of these just harvested will be replanted in August -- so I will need to figure out if I need to chill then warm or how to get them to know it is time to grow. I hope to have 2-3 fall beds of potatoes, and I have a bed of sweet potatoes too
This bed will be planted to field corn this week sometime, once mulch has been hauled out to it, it needs it for sure now. So, the yield per square foot is not done yet, that is why the short season potatoes, and it will be the short season field corn, lavendar mandan, which is a 70-80 day to maturity dry corn. Short 4 foot stalks. Sometimes I start the corn in a pot then transplant once the bed is ready to save time, or at least soak and sprout out in a jar on the counter.