How would you characterize the situation of the agricultural technology around the time of the Yellow Turban rebellion (A.D. 184-205), when technological breakthroughs were yet about to come?
Although the wikipedia article notes that a major cause of the rebellion was an agrarian crisis, note that famine is often caused due to factors other than agricultural production alone. Often bad distribution, heavy taxes and low market prices for agricultural produce cause famine.
While it may look like agricultural technology was in its infancy then, remember that (parts of) China was one of the earliest agricultural centers. Geography and climate combined to create conditions for the agricultural revolution in China. And there were comparatively great advances made specifically in the period (Around 220 B.C to 200 C.E.)
Background From Neo-lithic age:
Current research states that there were six more or less well-attested centers of origin for the Neolithic agricultural revolution. One of these is the Chinese Center, which was first constructed in northern China 8500 years ago on the loess terraces of the middle Yellow River, then was completed by expanding toward the northeast and southeast between 8000 and 6000 years before the present.
Between 5000 and 3000 years before the present, i.e., between 3000 and 1000 B.C.E., the world population doubled, growing from around 50 to around 100 million individuals. This increase can be explained, to a certain extent, by the extension of slash-and-burn cultivation. ...In the course of the two millennia that followed, between 1000 B.C.E. and 1000 C.E. the world population more than doubled to around 250 million inhabitants, due to the development of hydraulic systems of aquatic rice growing in the valleys and deltas of China, India, and Southeast Asia and, to a lesser degree, to the development of systems of hydraulic agriculture (Olmecs, Mayas, Aztecs, pre-Inca societies) in America during this period.
In China, the very first hydraulic city-states appeared in the second millennium B.C.E, in the middle Yellow River region situated close to the Chinese center of origin. These cities were united into the first embryonic empire under the Shang Dynasty (seventeenth to eleventh centuries B.C.E.). However, historians speak of a true wet rice-growing civilization beginning only in the following period (eleventh to third centuries B.C.E.), during which ten hydraulic and wall-building kingdoms were formed and fought one another until the most powerful among them, the Qing (from 249 to 206 B.C.E.) imposed its supremacy and administration to all of China, from the Great Wall to Canton.
Rice growing spread to hilly areas. The slopes of high valleys were cultivated through the construction of step-like terraces, which could be stretched out along contour lines.
The rice-growing regions in China are rain-fed due to the monsoons. The cultivation of Asiatic rice (Oryza sativa) next spread to all of the tropical and subtropical regions of Asia, and then to the hot temperate regions of Asia, Europe, and America.
Beginning in the Bronze Age, some metallic hand tools (knives, small axes, points of digging sticks) were made, though they were still not very effective. Beginning with the Iron Age, new, much more powerful tools (axes, hoes, spades, iron-tipped sickles) were made and used more and more widely in the agriculture of the “Old World.”
Moreover, thanks to the progress of artisanship in iron and wood, new equipment (ard, packsaddle, cart) made it possible to use animal energy. At the end of antiquity, cultivation with the ard was used in hydroagricultures and in systems based on fallowing in the most advanced regions of the Near East, North Africa, Asia, and Europe, while carts, wagons, and chariots, originating in Asian pastoral societies, were already used for transportation and war.
The Period in question:
Between 221 B.C.E and 220 C.E. the Qin Dynasty and the following Han Dynasty brought significant technological advancements and government policies relating to agriculture that affected China for two thousand years.
The period preceding the Qin Dynasty (Ch’in; 221-206 B.C.E.) in China was called the Chan-kuo (Ch’an K’uo), or Warring States Period (475-221 B.C.E.). All Chan-kuo states used iron for implements and weapons and irrigated and fertilized crops. These iron implements were crude but vastly superior for clearing and tilling land than their stone and wooden predecessors. The largest irrigation systems were found in the state of Qin, but extensive irrigation projects were not widespread until the Qin Dynasty and Han Dynasty (206 B.C.E.-220 C.E.). During the Chan-kuo period, suitable crops were matched to the soil and seasons, and rice was grown only in the southern region, which had naturally flooded fields.
Farming in the Han Dynasty was initially based on the Qin Dynasty model, i.e small farms using some irrigation and fertilization. But mostly they matched crops to natural soil conditions, and therefore relied on a limited number of crops. But during the two Han Dynasties, new crops were added: several cereals, beans, rice, barley, oats, wheat, millet, vegetables, hemp, indigo, sesame, mulberries, and gourds. The farms became well organized and productive, and crop rotation and intensive agricultural techniques and implements were developed.
Irrigation systems were developed.
Fifty-six water control projects for irrigation and land reclamation have been documented during the Han Dynasty. The largest were created by imperial proclamation and involved tens of thousands of laborers working for years. Smaller systems were built by local administrations and private investors. These systems spread throughout the country.
There were advanced engineering technologies such as dams, complex networks of troughs and trenches, windmills, siphons and waterwheels to raise water from lower to higher levels.
Two new dry-farming and one new wet-rice-farming technique contributed to much higher productivity for Han farmers. The dai tian (tai-t’ien) method of “ridge farming” and The ou zhong (ou chung) method of “pit farming” made it possible to farm land that was marginal or too small for conventional plowing and reportedly resulted in dramatically increased yields.
Although implements of the Western Han Dynasty were were relatively small and fragile, by the Eastern Han Dynasty, there had been a breakthrough in iron technology. This resulted in greatly improved high-grade wrought-iron implements during this period. Han plows were made in many sizes, materials and with new designs. This made deeper plowing and the use of new farming methods such as dai tian practical. The government-owned iron foundries also produced and distributed other high-quality implements, such as sickles, spades, and hoes.
On the whole it seems that for its day agricultural technology was pretty advanced in the time and geography in question.