Cells in agar in an incubator. Anything above that scale is bound to have losses and fails. How much depend on how controlled your environment is.

Cannibalism.

To answer your question. When Agriculture was first "discovered" by humans ~20,000 years ago, the most stable production method was diversification. You should have a variety of crops with overlapping growing seasons and overlapping macro nutrients. For even more security, introduce animal husbandry that can graze on your fallow land and if you have enough land make sure to have multiple distinct herds that never interact with each other except for breeding every few years.

Additionally ensure your food production isn't dependent on a single harvest season, nor a single climate. Have fruits/legumes/etc other lower yield crops that can be substituted in case your primary grains are hit with blight, or some other environmental factor.

Now let's introduce some technology. Create several fast growing monocultures that allows you to get multiple harvests in a season that can be used for animal feed, storage and supplementing any deficiencies in the primary human food supply.

tl;dr. Make sure you have multiple methods of food production that are all viable at different times of the year. Ensure that the failure of any one or two of them isn't a problem for overall yearly production, and ensure that they are independent on each other.

Photosynthesis

Foraging if done in a low density area. Natural food sources grow in an extremely diverse way and any blight or parasite will only ever effect a portion of edibles around you.