Identity and the surviving biographical evidence
Jia has no complete biography in the early dynastic histories. The attribution attached to Qimin Yaoshu names him as a governor of Gaoyang under the Northern Wei. Researchers therefore reconstruct his career largely from references inside the book and evidence about people whom it mentions. The Institute for the History of Natural Sciences places his activity in the first half of the sixth century.
Descriptions of crops around Bingzhou, Chaoge, Shangdang and Jingxing locate his practical interests across the middle and lower Yellow River region. More than one contemporary commandery bore the name Gaoyang, leaving the location of his office unsettled. His descriptions of agricultural work are firmer evidence than a detailed modern itinerary or an exact lifespan would be.
Reading, interviews and practical checks
In his own preface Jia explains that he gathered material from classical writings and songs, questioned experienced elders and checked practices against what people actually did. He arranged the resulting material into ten volumes and ninety-two chapters, extending from field cultivation to vinegar and fermented meat preparations. Contents lists were intended to make the collection usable.
Practical failure also entered the record. Jia describes keeping two hundred sheep and losing more than half when their feed was inadequate. The discussion turns to planting fodder in advance and cutting it at an appropriate season. Reports of transplanted crops that grew without producing grain similarly connect advice to local conditions rather than presenting every method as universally successful.
Organizing agricultural knowledge
Jia's organization begins with working soil and selecting seed, then moves through crops, trees, livestock and processing. The arrangement connects operations that a farming household had to coordinate: cultivation supplied feed and ingredients, while storage, fermentation and preparation determined what could be preserved and used.
The preface also states limits. For some plants not cultivated locally, he retained names without supplying growing instructions. Commerce and flowers valued only for appearance fell outside his main selection. Such decisions make the book evidence of a particular author's practical priorities as well as a large repository of inherited techniques.