In environments where water and vegetation are scarce, the goal of farmers is to avoid losing rainwater to runoff and evaporation as much as possible. It is not enough to slow down runoff by placing earth or stone or vegetation barriers, I discussed in the article "Traditional techniques I. Slowing, spreading, retaining water runoff and facilitating water infiltration". It is also necessary to capture the water and concentrate it in small spaces where the cultivated vegetation can flourish.
Shaping basins, holes or patches with runoff catchment areas is one way to achieve this goal.
In the Sahel and other semi-arid zones, a very old practice consists of making small, regularly spaced cultivated basins surrounded by catchment areas devoid of plants. The landscape thus shaped by humans resembles a succession of small oases.
The type of agricultural landscape that results from these developments is likely derived from observation of nature. Indeed, the plants of arid climates are not distributed uniformly, but in patches or zebra stripes according to the relief and folds, crevices, hollows, holes where water is concentrated.
This modality of distribution of natural vegetation in arid environments has been particularly studied by Doyle McKey, professor of ecology at the University of Montpellier in France. Noting the proximity of naturally self-organized designs to those constructed by humans in the same context, he developed the concepts of biocultural landscape and biocultural interactions.
To understand the "eco-logic" of the systems set up by farmers in semi-arid countries, let us first be guided by Doyle McKey to perceive how the landscapes of these areas self-organize. The figures below show the regular landscape types encountered in semi-arid environments.
The previous three shots show the repetition of a blotchy pattern. This "spotted bush" pattern is found in the flat landscapes of the Sahel and other semi-arid areas around the world.
Here, the bush is no longer "spotted" but "tigerized" with concentric and labyrinthine vegetation patch patterns. This natural "design" is typical of sloping landscapes, and patterns.
The principle that results in these particular distributions of vegetation in arid areas, Doyle McKey explains, is as follows:
"In these environments, there is a critical environmental resource or factor that constrains the distribution of organisms. Some organisms, which are referred to as engineers, have physical or chemical effects on the structure of the habitat, they change the distribution of that resource and concentrate it in tasks, with resource-free spaces between those tasks. In semi-arid environments, the critical resource is water [...]
In the examples, above the organisms driving this self-organization are plants. This regular pattern is not the project of a community of plants, but an emergent property of the interaction of each individual plant with its environment.
In these semi-arid environments, plants, through their roots, create porous soils. But between the plants, the soil is crusted. Also, between plants, the roots extend over a much larger radius than the plant canopy. Near a plant, the soil is porous and water seeps in. This moist soil encourages the establishment of other plants. This is the short-scale positive feedback.
Further away from the plant, water flows horizontally over the crusted soil until it reaches the vicinity of a plant, where it seeps into the porous soil. The water is thus assimilated by the roots, and the soil between the plants remains dry, preventing the establishment of other plants.
In a way, a group of plants can only become established from a minimum distance from another group of plants. This leads to a regular spacing with a distance between patches determined by the scale of processes set in motion by the "ecosystem engineers". The crusted soil between the plants collects water that leaks laterally onto the plants, and once the water reaches a plant laterally, it immediately infiltrates. The water is stored where there are already plants. The crusted soil, in combination with the plant roots, creates a system that concentrates water where plants are already located.
The patterns provided depend on the topography. On flat landscapes, water flows horizontally. This is called isotropy, because there is no favored orientation: the water flows in all directions. This gives rise to spotted bushes. On slopes, water flows along the slopes, this is called anisotropy, because there is a favored orientation. This produces bands of vegetation that follow the contours: the tiger bush. The space between patches is determined by the area needed to harvest enough water to allow another band of plants to grow.
At the ecosystem level, the result of all these processes is that plants, interacting with the physical environment, concentrate water in patches, and remove water between patches. This mechanism of resource concentration allows plants to grow in places where, if rainwater were evenly distributed, plants would not be able to grow. It is only through this resource concentration mechanism that plants persist. In fact, the zai system, which was invented by farmers in the Sahel, incorporates these same resource-concentration mechanisms that produce the naturally occurring regular landscapes in the same environments."
The traditional agricultural practices known as "zaï" in Burkina Faso cited by Doyle McKey, as well as similar practices "tassa" in Niger, "towalen" or "wégou" in Mali, replicate the principle of self-organization of "degraded" Sahelian dryland ecosystems. These ancient practices have become popular again after having more or less fallen into disuse during the colonial and post-colonial periods.
It is remarkable that they have been maintained or revived by some farmers in opposition to a frequent recommendation by agronomists to rehabilitate Sahelian soils by destroying their encrusted surface so that water can infiltrate.
Farmers refused this solution, which seemed logical and undoubtedly necessary to modern agronomists. For the farmers, the soil between the plants should not be touched and a porous soil enriched with organic matter should be created only where the plants are grown. Their genius was to preserve this crusted soil between the plants and use it to harvest the rain that flows to the plants where it will infiltrate.
In an edifying way, the ecologist continues, farmers who apply and develop ancestral technical systems of cultivation in dug pits form mottled cultivated landscapes on the flat areas, and mottled landscapes on the slopes, exactly as nature does. These are really striking similarities."
Thus, cultivated areas appear as successions of mini-cultivated areas each with a microcatchment area for capturing runoff.
In addition to water, these impluviums retain soil particles and organic debris that help form a fertile bed for plants, partially sheltered from the sun and wind. The more humid and protected microclimate of the growing basins allows the plants to wait for the next rains.
This technique would have been developed for the first time, 3000 years ago by the Nabateans in the region occupied today by Palestine, Israel and Jordan. Some researchers suggest that after the introduction of Islam to the Sahel, the movement of pilgrims to Mecca through Sudan and Egypt, two areas rich in water collection traditions, may have favored the spread of the cultivated pit technique. But it is also possible that these techniques were purely endogenous and based on the observation of the environment.
We shall see at the end of this article that this type of cultivation in pits was also practiced in Northern China where it appeared more than 2000 years ago.
Sahelian Patterns
Zaï, tassa, towalen and wegou
In Moore, "zaï" would mean "to hurry", implied in this context to dig in the dry season a packed and crusted soil. In Niger, these small cultivated pits are called "tassa": "small cup" in the Hausa language, in Mali the Bambara speakers call them "towalen" and the Dogon "wegou". In English, cultivated holes are called "planting pockets", "planting basins", "micro pits" or "small water harvesting pits". French speakers tend to use the name "zaï".
These evenly spaced pit farming systems are most common in areas where soils are sloping, i.e., covered with an impermeable hardpan, and where rainfall is low and highly variable. Basin cultivation is often combined with other methods of runoff retention such as stone bunds. Since the 1980s, these traditional techniques have been rehabilitated and recognized as relevant endogenous responses to the fertility and moisture problems of these crusted soils.
Zai holes with stone lines
In the Sahel farmers do not have sufficient quantities of organic matter (straw, manure...) to cover the soil. Moreover, if they spread manure in their fields, much of it would be "cooked" by the sun, blown away, and carried away by the winds. Cultivating in small planting pits mulched with crop residues and concentrating available manure in them during the dry season is an appropriate response to this context.
Mulching the planting pits leads to an increasing activity of termites which, by digging galleries under the pit, loosen the soil in a remarkable and stable way and increase the rate of water infiltration when the rains come.
In addition, the holes in which millet or other plants are sown protect the seedlings from the drying effects of the wind, which can reach 100 km/h at the beginning of their growth.
In summary, crop pits concentrate and protect scarce resources (water and organic matter) and improve poor, bare soils in drylands, crop by creating a microenvironment and microclimate that locally changes soil structure and composition, increases drought resilience, and ultimately improves yields of crops such as sorghum and millet, potato, and beans.
To increase, water catchment by crop pits, Mossi Burkinabé farmers install their zai crops near a natural basin dug at the bottom of a glacis that accumulates runoff before it is redistributed to cultivated fields.
Corn and bean in a zai hole
In East Africa, the Tanzanian "chololo" system (named after the ecovillage that initially adopted it) and the Kenyan "Tumbuzika" system advocated, for example, to boost production of Napier (elephant grass) fodder are recent variations on the pit cultivation principle.
Elephant grass in a conventional field on the left, and in Tumbukiza pits on the right
Elements of evaluation
Evaluations conducted in Burkina Faso show that the properly conducted zaï system improves cereal yields, which have been able to increase from 700 kg/ha to 1,000 or 1,700 kg/ha depending on the soil and rainfall. Farmers who have adopted this technique recognize all the advantages of this technique, which has helped to double or even triple grain yields. This has resulted in food security over a longer period of the year (8-9 months in the case of poor rainfall and 12 months in the case of good rainfall), and sometimes in a production surplus over several years.
In Niger, fields on which tassa is practiced are twice as productive as fields that have not benefited from this work. For example, a millet planted in a field with tassa can have 4 to 7 tillers, whereas a planted in a field without tassa will have only 2 to 3 tillers. The only constraint is obtaining sufficient organic fertilizer for the tassa.
At the end of the 1998/1999 cropping season, millet yields on fields treated with tassa and manure were 1200 kg/ha at Sansani Tabla (Filingué) with a cumulative rainfall of 560 mm, and 800 kg/ha of sorghum at Tadeni Béri (Filingué).
A study conducted in the Tahoua region by CRESA indicates that the rate of adoption of this technique is around 97% for farms in the Batodi area, 91% in Kolloma and 77% in Adouna. The criteria underlying this appropriation by local communities are the simplicity of the technique, the direct benefits derived from the application of the technique, and its capacity to transform uncultivated, indurated or glaciated land into productive land.
Field cultivated with zaî
In summary zaï / tassa / towalen / wegou present the following advantages and interests:
– they increase the cultivable areas by rehabilitating uncultivated land ;
- they significantly increase yields
– it’s an endogenous technique well mastered in the Sahel;
– zaï can be combined with other techniques such as stone barriers or "embocagement"
– it can be used for reforestation
– it require only a small investment.
This technique presents the following disadvantages and constraints:
– There is a risk of wilting of young plants in case of drought or asphyxiation in case of heavy rainfall (particularly for millet and cowpea);
– the short "life" of the zaï makes it necessary to restore them regularly;
– the good functioning of the system requires the contribution of important quantities of organic matter and manure.
Evolution
A proposal for a "luxury" zai is offered on the website reforestation.me.
This proposal for customizing the traditional zaï is interesting, but its implementation seems to me to be possible only on a small scale, in a kitchen garden or in urban "agriculture" for example.
Notable African variations of hollow culture
Among the different African modulations of pit farming, two variants are noteworthy: the "half-moons" used in the Sahel and the "ngolo" pits of the Matengo of Tanzania, which enabled this people to cultivate the steep slopes lacking in arable land in the highlands where they once took refuge.
Half moons
Half-moons are cultivated pits in the shape of a semicircle dug perpendicular to the slope. Like the zaï, they are most often placed on glacis to collect runoff water and facilitate its infiltration in circumscribed areas where the soil has been loosened by removing its hard surface. The soil thus removed and placed at the edge of the curve of the structure forms a small dike. These half-moons are used to grow vegetables, grain, fodder, or even trees.
Half-moons with mulch in Niger
The half-moon dikes which can be reinforced with stones are 30 to 50 cm high and 2 to 8 m or even 12 meters in diameter. The tips of the dikes, pointing upwards, are aligned on a contour line.
The half-moons are established in staggered rows, so that each line of half-moon receives the water that runs off between those of the previous line and so on. In dry areas, they are larger, and in wetter conditions, more smaller half-moons are built per hectare. This technical system is rarely used on slopes of more than 5% or that receive more than 300 mm/year of rain.
Small, tightly packed half-moons are used to grow trees and shrubs. In the Sahel, they are used to grow small millet. The larger, more widely spaced half-moons are used more for pasture rehabilitation or forage production.
Where they are used to grow trees in agroforestry systems, with a single hole dug at the lowest point, they act more like negarim (a water catchment technique practiced in the Middle East).
The implementation of half-moons implies a greater intensity of work than that of zaï. It assumes that neighborhood solidarity can be mobilized. The counterpart of the collective work of installing half-moons is that the works carried out are more resistant and durable over time than the zaï (5 to 7 years against 3 years) and more productive. The application of this water and soil conservation technique provides its beneficiaries with the opportunity to vary their production by producing crops that would otherwise be unthinkable because of the aridity of the soil. For the community as a whole, the installation of half-moons allows the groundwater table to be recharged and the water in the wells to be brought up.
Elements of evaluation
Souleymane Ganaba (2005), who conducted an evaluation of different soil restoration techniques, reports that the half-moon arrangement associated with subsoiling or scarification is the work that allows for the best regeneration and reconstitution of woody cover. For this researcher, the half-moons as well as the stone cordons are suitable for the recovery of natural pastures as well as cultivated lands. The presence of macroscopic fungi in the half-moon plots is a biological indicator of a better water condition that is not found in the control plots or in such abundance in the other arrangements.
A recent development in agronomic research has been to study the effect of combining traditional techniques. This is the case of the study conducted by Maman Nassirou et al. (2021) who compared the performance of three systems:
–a plot laid out in zaï of 30 cm in diameter and 20 cm in depth was installed in staggered rows perpendicular to the slope at spacings of 70 cm and 100 cm respectively on and between the rows.
–A "conventional" half-moon plot, 4 m in diameter and 20 cm deep, was installed perpendicular to the slope at a distance of 4 m on the same line and between two adjacent lines. The excavated soil was deposited on the semicircle in a semicircular bead with a flattened top.
–A plot that the researchers call "multifunctional half-moons" in which the inner soil of the half-moons is not excavated as usual, but incorporates sixteen zai arranged in a staggered pattern and three trenches usually used for reforestation, one meter long and fifty centimeters wide and deep. These "multifunctional" half-moons were laid out in the same manner as the conventional half-moons.
Zaï, "conventionnal half-moon" and "multifunctional half-moon"
Sorghum was grown simultaneously for two growing seasons in 2019 and 2020 in each of the setups with differential effects on both biomass and grain production.
Sorghum grain yield was significantly higher in the multifunctional half-moon structures than in the conventional half-moon structures and in the Zai at the end of each cropping season. Sorghum grain yields were as follows:
– 189 kg/ha in 2019 and 691 kg/ha in 2020 in the Zaï
– 497 kg/ha in 2019 and 1858 kg/ha in 2020 in conventional half-moons
– 639 and 2159 kg/ha in 2020 in the multifunctional half-moons
The improvement in productivity with zaï and half-moons is usually explained by the increase in the amount of water stored in the soil profile near the plants, which further increases the availability of water in the root zone of the crops. In addition, the decomposition of organic matter added to the structures is considered to improve soil structure, promote infiltration, and increase the availability of nutrients to the crops. The different performances of the different structures would therefore be explained by the improvement of these parameters.
In fact, the simple zaï have a smaller impluvium than the half-moons, where the water collected is distributed over the entire surface of the structure’s excavation. In "multifunctional" half-moons, the collected water is concentrated in the subworks - zai and trenches - intended for crop pocks which optimizes the use of nutrients and runoff collected by the crops.
In summary half-moons present the following advantages
– they effectively mobilize runoff water ;
– they contibute to recharge the water table ;
– they improve soil structure and fertility;
– they increase the cultivable surfaces in regions where the degradation of the productive base is very advanced.
– they can be interestingly combined with other techniques such as zaï and reforestation trenches;
– they significantly increase yields in semi-arid areas
– they can be used for reforestation
This technique present the following disadvantages and constraints:
– they require regular maintenance
– tehy require a large workforce to be implemented
These constraints become opportunities if they are an opportunity to rebuild local solidarity and collective organizations.
Rehabilitation and reforestation by stone lines, zaï, half-moons
Farming around pits - Matengo ngolo system
In southwestern Tanzania, the Matengo communities of Mbinga District who live in the highlands are descendants of communities who having been driven out of the surrounding plains once took refuge in rugged mountainous areas. To ensure their livelihoods, the refugees from the plateau invented a labor-intensive farming system to make the most of a steeply sloping, arable land-deficient environment. This system, which has been in use for at least one and possibly two centuries, is called "ngolo" (or ngoro) or "Matengo pits.
The ngolo or Matengo system can be considered a soil and water conservation system as well as a technique for building fertile soils through the ingenious use of weeds and crop residues. The main principle of this system consists in the construction of series of cubic cultivated pits of varying depths that resemble a chessboard from a distance. Unlike the "zai system" and the half-moon system discussed above, cultivation is not done in the pits but on their edges.
Typical mode of occupation of a hillside by the Matengo
Before outlining the Ngolo technical system, let us see how it is integrated into the overall agroecosystems shaped by the Matengo.
The Matengo build their home on a "nnduwi", a flat site within the "ntambo" plot they occupy, and plant a kitchen garden around the house to grow tomatoes, onions, amaranth, sweet potatoes, sunflowers, pumpkins and other vegetables. In recent decades, coffee trees have been planted around the kitchen garden.
The mountain tops are often kept covered with forest (kitengo) which stabilizes the soil and is used for gathering firewood and medicinal plants and for grazing, or collecting wild plants for herbal remedies.
On the steep slopes, "uheleu," below the coffee gardens, ngolo fields are cultivated for the main food crops: corn and beans.
The narrow "kijungu" or "libindi" plains along the waterways, which remain wet year-round, are used to grow some vegetables and coffee plants. The Matengo also grow a variety of perennial crops, such as sugarcane, bananas, and taro, or keep part of the plains as pasture during the dry season.
Confection of ngolo fields
The ngolo fields are thus laid out on steep slopes ranging from 10 to 60%. The average size of a ngolo field is about 0.7 hectares. Pits occupy about half of the area of a given field, the other half being occupied by ridges on which beans, maize, and cowpeas are sown. Ngolo cultivation is mostly practiced on steep slopes ranging from 10 to 60%. The average size of a ngolo field is about 0.7 hectares, and the size of a ngolo varies from 1 to 2 m². Thus, there may be more than 1,500 pits in a typical ngolo field.
Schematic sketch of the ngolo cropping system showing the arrangement of plants on plots.
Size of ngolo pits: (a) 1 m × 1 m, (b) 1.5 m×1.5 m (c) 2 m x 2 m.
● = inner rows - X = outer rows.
The preparation of ngolo begins with the mowing of weeds with a sickle, or a machete at ground level, the grasses are arranged in a checkerboard pattern after drying for 10 to 14 days. Then the earth is dug with a hoe in the center of these squares and thrown over the grass to form dikes on all sides and consequently a ngolo pit in the center. The low earthen walls surrounding the ngolo are thus made of a layer of dried plant material sandwiched between the topsoil layer and the original soil surface below.
Among the Matengo, the preparation of ngolo fields is generally based on a division of labor between men and women. The men cut the grasses ("kukyesa") and arrange them in square matrices ("kubonga"), while the women shape and cultivate the ngolo ("kulema ngolo").
In February, at the end of the rainy season, various weeds, collectively called "malumba" (including Nidorella resedifolia, Conyza persifolia, and Hypharrhenia coleotricha) flourish and bloom at the same time.
Hypharrhenia coleotricha
In early March, men cut the malumba weeds with serpettes and machetes ("gesela", "mbopo"). Cutting the tall Hypharrhenia coleotricha weeds, which grow to about 2 m high, is a tedious task.
The cut grasses are left to dry in the fields for 10 to 14 days. The dry stems are then collected and arranged in vertical and horizontal lines to form checkerboards. This preparation is called "kubonga"; the lines formed by the bundles of dry grass are called "mabongi". The excess grass is collected in piles which are then burned.
After completing kubonga - arranging the grasses in square matrices - the women proceed to the next step: "kujalila": they dig the earth with the hoe in the center of these squares delimited by the bundles of weeds and throw it on this mulch to form dikes on all sides and consequently a ngolo pit in the center.
The earthen walls are thus made of a layer of dried vegetation sandwiched between the topsoil layer and the original soil surface below. Buried under the ridges, the straw-like mabongi will amend and structure the soil and provide internal drainage.
The figure below shows the sequence of work.
Once the topsoil has been evenly spread over the mabongi, the women sow seeds of beans or another legume (kukweta ngondi) into it. Finally, they cover the seeds with soil from the pit (kukulila). Maize or cassava will be sown after the legumes have been harvested. The seeds are sown at an interval of 15 cm for legumes and 30 cm for maize.
The task called "kukulila" is similar to kujalila, but refers to a deeper tillage of about 15 cm. According to the women, moving the soil upstream (letters a-d and i-k in the figure) is physically difficult. The first clods of soil are placed on location a, b, and i before placing more on c, d, and j and on the upper spaces between a, b, and i.
The first shovelfuls of soil are for the ridge foundations and the second shovelfuls are for connecting the larger clods. This task is intended to strengthen the horizontal earthen lifts perpendicular to the slope. Thus, consolidated, the ngolo can withstand heavy rains.
Throughout the year, weeds and soil and crop debris are thrown into the pits to form compost. Once the beans are harvested, the dry bean stalks are also put into the pits and buried with the other plant residues. Each ngolo is thus a compost bin. The soil is lightly raked to remove weeds and crop residues before planting maize and cowpeas.
The Matengo define an ideal ngolo field as having pit dimensions of 3.5 m2×70 cm deep, with an adequate amount of mabongi buried. Under these conditions, ngolo cultivation effectively conserves soil and water and maintains soil fertility. Women are the custodians of the techniques for making the ideal and perfect ngolo. Their ability to make and cultivate ngolo provides special status and recognition, especially for unmarried women.
Maturation of a fertile soil thanks to the ngolo
The soil in the Mbinga district is mostly red clay, which the Matengo call "luhumbi lukeli. An important effect of the ngolo farming system is the formation of darker soil layers due to the repeated mixing of mabongi into the deep soil; this dark soil rich in organic matter called "luhumbi lujilo" is favorable to high crop yields.
In this system, the fertile soil in the pits is turned over on the ridges every two years, while the red subsoil that is dug to compensate for soil losses is placed on the horizontal ridges to reinforce them (clods c, d, and j in the figure seen above). The part of the red soil "luhumbi lukeli" that appears on the ridges transforms over time into the darker soil "luhumbi lujilo" by being mixed with the organic material "mabongi".
Soil and organic matter are regularly stirred as the position of the pits is moved for each new crop. The new pits are placed at the intersection of the previous ones. By changing the position of the pits, the top and bottom soils and dry grasses are mixed or turned. This process "matures" the soil. Digging new pits allows the stems to decompose in the previous filled pits. Plant growth and productivity are always better in areas where the stems are buried.
Topsoil from the original vegetation (miombo forest) and topsoil from a ngolo field were analyzed at Lupilo village, east of the district. Results showed that clay occupied about 50% of the topsoil of the ngolo field and 35% of the miombo forest. This is mainly due to the integration of part of the subsoil into the topsoil by the ngolo crop. In addition, the soil structure is stabilized by the decomposition of straw-like organic matter by bacteria and fungi (Russell, 1988). The topsoil forms water-stable aggregates suitable for cultivation through a process of organic matter integration.
Evaluation of the ngolo system
Z.J.U. Malley, B. Kayombo, T.J. Willcocks, and P.W. Mtakwa who evaluated the ngolo cropping system conclude their study as follows:
(1) Ngolo production systems efficiently conserve water, soil, and nutrients on sloping land. Net soil loss is negligible, as eroded soil is mainly redeposited in the pits. The durability of the steep slope system is evidenced by the continued use of ngolo to conserve sole for over two centuries.
(2) Pit size does not significantly influence the soil moisture regime;
(3) In contrast, a larger pit size generally results in an edaphic environment (relative to the soil as a biological medium) that is more favorable to crop root growth; root resistance to soil penetration is reduced with the 2m ngolo.
(4) The 2m × 2m pit size yielded the highest grain yield of 1.85 t/ha.
(5) Increasing the pit size reduced labor requirements for construction and significantly increased the profitability of the system (ninefold in this study).
(6) Larger pit sizes should be encouraged, especially on steep slopes."
Thus, the Ngolo system has multifunctional benefits: building and maintaining soil fertility, harvesting and trapping water harvesting wateritu; controlling and using weeds as a fertility aid, and conserving soil through the combined effects of intercepting runoff water and trapping eroded soil particles in situ in the pits, and structuring a resilient soil through the incorporation of straw into the soil.
Agriculture in pits in northern China
Outside of Africa, the principle of cultivating in holes can be found in China. This ancient method is called "ou-chung" or "qut’ien". It was particularly developed during the Han dynasty in the overcrowded plains of the northern part of the empire to cultivate wheat and millet or vegetables.
This technique was promoted by the famous Han Dynasty agronomist, Fan Shengzhi, who is said to have been asked by the emperor to write a treatise on agriculture to help farmers with limited resources learn the best farming techniques. This treatise, written in the first century BCE, is known as "Fan Shengzhi shu": "The Manual of Fan Shengzhi."
Fan Shengzhi
Fan Shengzhi describes the hole cultivation technique as follows:
Shallow-pit compartment fields (qutian 區田)
Cultivation in shallow pits depends mainly on the fertilising power of the soil, therefore, by principle it needs not good land to start with. Mountain, high cliff, steep places nearly villages and even the inside slopes of the citywall can all be used and shallow pits made thereupon.
In planting the shallow pits, it is essential to concentrate the power of the soil, so the adjacent grounds should not be cultivated. Cultivation in shallow pits starts directly on the waste land, no need to begin with other preparatory work.
Take one mu (see note on weights and measures) as a standard: One mu is a piece of land 18 zhang long and 4 zhang and 8 chi wide. Divide the mu into 15 parcels, and leave 14 alleys in between as footpaths... Traverse the parcels with straight ditches across. Ditches are 1 chi wide, 1 chi deep and 1 chi apart. The loose earth [taken out in digging] is deposited between them. This deposit will form piles 1 chi wide. If the spaces left between the ditches cannot accommodate the loose earth, widen them to 2 chi.
To plant spiked and glutinous millet: Sow them in two rows along the flanks of a ditch. Individual plants are 5 cun apart, and rows 5 cun apart and 2.5 cun away from the ditch. One ditch thus takes up 44 individual plants, and the whole mu now takes up 15,750 plants altogether.
After sowing the millet seeds, cover with 1 cun of earth—neither must the layer be more nor less than 1 cun.
With this system of cultivation in shallow pits, one must always see to watering of his crop in days of draught. A yield of 100 hu per mu may be expected.
Translation from chinese according to Shih 1959: 31-33.
Note on measures:
– one mu 1/15 of a hectare, or about 675 m2
– one zhàng 3.2 m
– one ch’ih : 23 cm (one foot)
– one t’sun 3 cm (one inch)
– one hundred hu 5 m3
While the manual Fan Sheng Zhi Shu contains the first Chinese description of hole cultivation, oral history suggests that this technique is much older, dating back to the 17th century BC. Legend has it that at that time, the Thang Emperor, the famous founder of the Shang Dynasty who unified the very first Chinese city-states in the Middle Yellow River region, ruled. A great drought occurred, burning the crops and starving the people. It is then that the technique of cultivation in holes was elaborated which greened the fields and saved the population. This practice would be maintained thereafter while remaining marginal, until it was revived by Fan Sheng Zhi.
Farmers in northern China would then have found that pit cultivation was particularly suitable for developing semi-arid areas and plot lands that were too small or too impractical to be plowed. As in Africa, this technique was used on slopes, and the uncultivated space between the pits acted as a small impluvium. But it proved equally effective on flat land and poor quality soils. The practice of cultivation in small pits thus developed on the plains as well as on the hills and near urban centers, even under the city walls.
The size, depth and spacing of the cultivation pits varied according to the needs of the different crops. For example, wheat or millet could be grown in pits six ts’sun in diameter, six ts’un in depth, and nine ts’un in distance on prime soil [10 x 10 x 10 cm pits spaced 30 cm apart], while melons required pits three chi (feet: 23 cm) in diameter, five ts’un in depth, and were so far apart that there could be only twenty-four pits in a mu (1/15 of a hectare). Regardless of the arrangement of the pits or the cultivation, the farmer had to keep the pits well irrigated and fertilized.
Fan Shengzhi, states that the yield per unit is incredibly high: "two people working on ten mu of land using pit cultivation are able to feed themselves for twenty-six years." The figures in the various parts of the Fan Shengzhi Shu text are inconsistent, however, experiments with pit cultivation conducted in China over the past few decades have indeed yielded interesting results: Experiments in Yanan and Dinxi showed that pit tillage could increase crop yields by 20-50%, sometimes even doubling them (Shaanxi Academy of Agricultural Sciences, 1973).
With pit farming, Fan Shengzhi promoted an intensive farming method that requires little land and no animal power, but a lot of labor and care to meet the needs of peasants cultivating very small plots of land. However, since much of the work could be shared with women and children, the method described by Fan Shengzhi made it possible to utilize the entire potential labor force of a household, thus turning the handicap of the poor peasant into an asset.
This method, which requires little investment but a lot of work, has remained marginal in China despite its high productive potential. Today, hole cultivation is mainly practiced on small plots because farmers often lack the manure and time to carry it out.
Its diffusion has not lived up to the hopes of Fan Shengzhi in the first century, nor to the enthusiasm of contemporary agronomists who have studied it and have been excited by its good performance. It is mostly developed in arid areas where water is scarce, because it ensures an otherwise almost impossible production. Elsewhere, it is practiced in a few large farms whose owners wish to recover poor land. When it is practiced to rehabilitate uncultivated land, it is similar to zaï.
Cheng-ou cultivation is also, for the large farmers, a way to occupy their abundant labor force when agricultural work becomes lighter. It is also said to be, for some of the Chinese who practice it, a source of aesthetic pleasure, for it enables them to draw geometrical shapes, a pastime they are reputedly fond of.
It is not impossible that the ancient ou-chung practice of hole farming will soon be the object of renewed interest in view of the ongoing climatic changes.
To end our world tour of cultivation pit farming practices, let us point out that the waffle gardens of the Zuñi in the south-west of the North American continent and the dogon checkerboard gardens are two other forms related to this mode of growing plants. I refer the reader to the two articles I have written on this subject.
Zuñi waffle garden
Dogon checkerboard garden
The practice of pit farming is also found in India, as evidenced by the photograph below, but apart from this visual document gleaned from the web, I have not found any other reference to this practice.
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