Different climates and soils result in vastly different crops. Yunnan, known as one of the world's most famous kingdoms of plants and animals, possesses unique natural conditions and boasts the greatest number and most unique species and food ingredients in China.  All of this is largely related to Yunnan's soil. Soil is the most fundamental ecological condition for plants; whether tea plants develop well, and the quality and style of the tea, are all significantly related to the soil in which they are cultivated.

Here, we will focus on two key points: 

Firstly, what are the main types of soil found in the tea-growing regions of Yunnan?

Secondly, what is the relationship between high-quality tea and soil?

Yunnan's tea-growing region is located on a low-latitude plateau. To the northwest are the high-altitude areas connected to the Tibetan Plateau, a part of the Himalayan mountain range.  The elevation gradually decreases towards the south, connecting to the low-altitude Indochina region in the southwest, south, and southeast, and is adjacent to the Pacific Ocean, the Gulf of Tonkin, the Indian Ocean, and the Bay of Bengal.  The large mountains of the Yunling range in the northwest block the invasion of dry, cold air from Siberia, and the Sichuan Basin diverts northern air currents, making the Yunnan tea region one of the areas least affected by advective cold fronts, resulting in a consistently warm climate throughout the year.  Two streams of warm, humid air from the Bay of Bengal and the Gulf of Tonkin repeatedly move northward during the summer. This climate offers two advantages:

Firstly, the alternating wet and dry seasons and abundant heat determine the basic characteristics and properties of the soil in Yunnan's tea-growing regions.

Secondly, these conditions promote the development of biological productivity and biodiversity in the soil, thereby driving biological soil formation and improving and developing the excellent characteristics of the soil in Yunnan's tea-growing regions.

This has resulted in the fertile natural soil of the Yunnan tea-growing region, and it is precisely because of this that the tea tree species originated in the land of Yunnan. Soil is the most fundamental ecological condition for the growth of tea trees, providing a substrate for growth, anchoring the roots, and providing support.  At the same time, it provides all the nutrients for tea tree growth except for carbon dioxide; approximately 40 different elements are absorbed from the soil, playing a vital role in the life activities of the tea tree. These elements influence the growth and flavor quality of the tea tree.

The normal growth of tea plants has some basic requirements for the soil. First, the soil needs to have a certain depth, preferably more than 1 meter, to facilitate the downward growth of the tea plant's roots. The soil texture should not be too clayey, nor should it be like sand that doesn't retain water.  In addition, the optimal pH range for the soil is 3.9–5.0, meaning it should be acidic. The soil should also be rich in various nutrients, have a high accumulation of organic matter, and possess rich biodiversity, meaning it should contain earthworms and various soil microorganisms. These organisms promote the circulation of soil matter and energy conversion, making the soil vibrant and healthy; we call this soil organicization.

Now that we understand the soil requirements for tea tree growth, let's look at the soil conditions in various tea-producing regions of Yunnan.  Yunnan's soil types can be broadly categorized into nine types: lateritic soil, red lateritic soil, red soil, mountain yellow soil, brown soil, carbonate soil, volcanic ash soil, subtropical meadow soil, and purple soil.  Among these, red lateritic soil is the most common soil type in tea plantations, followed by red soil and mountain yellow soil. The remaining soil types are generally unsuitable for tea tree cultivation.

Below, we will take you on a tour of some typical tea-growing regions in Yunnan from the perspective of soil ecology.

Yunnan's earliest tea-producing regions include the famous Six Great Tea Mountains within the river basin and the Six Great Tea Mountains outside the river basin.  In present-day Mengla and Jinghong counties of Xishuangbanna Prefecture, these six tea mountains form a continuous area.  Below 1500 meters in elevation, the soil is lateritic red soil, while above 1500 meters it is red soil.  Taking the Nanluo Tea Mountain, one of the Six Great Tea Mountains outside the river basin with a history of over a thousand years, as an example, Nanluo Tea Mountain is a typical granite region, and the soil types are mainly South Asian subtropical lateritic red soil and red soil. The highest point reaches 1898 meters above sea level.

The soil samples we collected that year were from Xiangyang Village in Nanluo Mountain, at an altitude of 1340 meters.  After research and comparison, we found that the soil in Nanluo Mountain is very fertile.  Firstly, the pH value is acidic, which is within the range preferred by tea trees, thus providing a favorable condition for tea tree growth.

The soil in the Nannuo Mountain tea plantations has very high levels of both organic matter and nitrogen. Nitrogen is considered the primary element of life, and if there is insufficient nitrogen supply, tea trees cannot grow properly. This can lead to slow growth, stunted seedlings, sparse foliage, dieback of the tips, yellowing of the entire leaves, and bud death.  Therefore, nitrogen content is arguably the most important indicator of soil fertility.

Soil tests in Nannuo Mountain show a nitrogen content of approximately 0.22% and an organic matter content of 6.64%.  These figures might seem abstract, so to put it another way, the nitrogen content in Nannuo Mountain tea plantations is about 2 to 5 times higher than in conventional tea plantations. The organic matter content is even higher, reaching up to 6 times that of conventional tea plantations. The humus layer is about 50 centimeters thick; walking on it feels like walking on a sponge. This should help you understand the unique characteristics of the Nannuo Mountain tea plantations. It boasts exceptionally favorable conditions in terms of geographical latitude, altitude, climate, and vegetation.  In particular, the geological background and soil ecology of Nanluo Mountain are among the best tea-growing areas in Yunnan Province, and such ecological conditions are rare throughout China.

In addition to other phosphorus, potassium, and numerous trace elements, and the fact that the soil in Nanluo Mountain is a medium-textured, heavy loam with excellent water retention and drainage properties, it's no wonder that there are extensive ancient tea gardens on Nanluo Mountain. With such favorable soil conditions, the tea from Nanluo Mountain naturally possesses a unique quality.

Besides the traditional ancient tea gardens of Pu'er tea, let's look at other tea gardens in Yunnan, such as the renowned tea gardens around Kunming, including Shili Xiang, Baohong Tea, and Taihua Tea.  These traditional famous teas from central Yunnan owe their reputation not only to their quality and processing techniques, but even more so to the climate and soil conditions.

Kunming is located on the central Yunnan Plateau and features a typical karst landscape with numerous caves.  The soil in Kunming is red soil, characterized by deep laterization. While red soils are generally deficient in phosphorus, the deposition of karst groundwater makes the soil more fertile than the Quaternary sedimentary red soils found in Central and Southern China. The organic matter content of this soil is approximately 3.38%, placing its fertility at only a moderate level among Yunnan's tea-growing regions. However, the soil in this region has a more comprehensive range of nutrients than that of the southern tropical regions.  All the elements necessary for the growth and development of tea plants are fully supplied, which has a very important effect on the final aroma of the tea. The tea has a refreshing taste, with a rich and fragrant aroma that is a blend of bean, tender, and sweet scents.

Besides Pu-erh tea and green tea, Yunnan also boasts another type of tea renowned both domestically and internationally: Dianhong black tea. In 1938, after conducting on-site investigations, Feng Shaoqiu discovered that the ecological environment of Fengqing was particularly suitable for producing black tea. The tea mountains in Fengqing mainly consist of yellow-red and yellow soils, with some areas having yellow-brown soil. Taking the representative Anshi Tea Garden in Fengqing as an example, the soil texture is good, with moderate bulk density and porosity. We call it weakly stony medium loam, with an organic matter content of 3.18%, which is considered moderate. However, it is very rich in potassium, and especially high in boron, resulting in overall superior fertility. These two types of elements are abundant, ensuring the foundation for making black tea. Phosphorus has a very significant impact on tea quality; it enhances the photosynthesis of tea plants, facilitating the accumulation of carbohydrates, especially polyphenols.  A high content of polyphenols prepares the tea for high quality. This allows for the production of black tea with a bright, vibrant red liquor and a strong, rich flavor after brewing, thus earning its reputation for quality both domestically and internationally.

Generally speaking, Yunnan's soils follow these patterns: pH values ​​increase with increasing altitude. In some low-altitude areas, the soil is prone to calcification, resulting in lower acidity. This can limit tea yield, but the soil may contain various trace elements that are beneficial to the formation of certain unique aromas and flavors in tea leaves.

Regarding soil fertility, organic matter and nitrogen content both increase with increasing altitude; the content at 2300 meters is twice as high as at 560 meters. However, soil temperature and biological activity show the opposite trend: biological activity is higher at lower altitudes.  Biological activity is very strong at 560 meters, moderately strong between 1100 and 1450 meters, and weaker above 1800 meters.

Specific climates give rise to specific soil types, and these soil types directly affect the quality and yield of tea.  Based on the soil requirements of tea plants, we have created a general classification of soils in Yunnan. The factors considered for the top-tier classification include: nitrogen content, pH value, gas-to-liquid ratio, and soil accumulated temperature. The "gas-to-liquid ratio" describes the soil's moisture and aeration, while the soil accumulated temperature represents the soil's heat retention capacity. These data points directly influence the yield and quality of our tea. Based on the different quality requirements of various teas, we have established three categories: black tea, green tea, and Pu-erh tea.

Regarding black tea, we observe that the best quality and highest yields are found in soils located around 22–23.21 degrees North latitude.  North of 25 degrees North latitude, the quality is poorer and yields are lower, meaning that the further south you go, the more suitable the conditions are for producing black tea.  From an altitude perspective, black tea produced in areas below 850 meters above sea level is of the best quality, characterized by a strong and robust flavor. As altitude increases, the soil becomes less suitable for black tea production, and in high-altitude regions above 1850 meters, black tea yields are low and the quality is milder.

Based on soil surveys in green tea and Pu-erh tea producing regions, the area between 23.3 and 25 degrees North latitude is considered a high-quality zone, suitable for the production of raw and ripe Pu-erh tea, as well as general green tea.  The soil fertility in this region is ideal, resulting in high yields and excellent quality. North of 25 degrees North latitude, near Kunming, the area is suitable for green tea production, yielding high-quality tea but with lower yields.  In terms of altitude, the main high-quality Pu-erh and green teas are concentrated in high-altitude areas, with the best quality found between 1730 and 2050 meters.  At even higher altitudes, the quality tends to decline.

Finally, let's review a few important points:

The soil types in Yunnan can be broadly classified into nine categories: lateritic soil, red lateritic soil, red soil, mountain yellow soil, brown soil, carbonate soil, volcanic ash soil, subtropical meadow soil, and purple soil.  Of these, red lateritic soil is the most important soil type for tea plantations, followed by red soil and mountain yellow soil. The remaining soil types are generally unsuitable for tea cultivation.

The optimal pH range for the soil is 3.9–5.0, and it should also have rich biodiversity, including earthworms and various soil microorganisms. These organisms can drive the circulation of soil matter and energy conversion, making the soil vibrant and healthy.

We know that soil plays many important roles for tea plants, helping to anchor and support them, and providing them with nutrients, the most important of which is nitrogen.  The soil requires a certain degree of aeration and water retention. The soils in Yunnan suitable for growing tea trees are mainly lateritic red soil and red soil.