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A small-farm system for South China to offset drought, increase water resources, improve degraded lands, and expand income opportunities

Walter E. Parham, Ph.D.

July 2008

Introduction: Some seventy years ago in South Africa, C.M. Heanley, a field researcher and keen observer of nature, noted that the water flow from springs located at the base of previously barren hills increased after the hill tops were planted with pineapples. Further, he observed that fruit trees planted among pineapples thrived better during dry periods than where they were planted as monocultures. In Hong Kong, he observed that pineapple plants survived on the spurs of deeply weathered, granite hills where the “soil is so powdery and windswept that grass cannot maintain itself there” (Heanley, 1935). How can pineapples survive on such sites? How might we use the pineapple’s natural properties to improve degraded lands and their water resources? Heanley’s observations suggest that a closer look at pineapples might hold some promise for solving the problems of the small farmer in South China today who faces six months with five or six feet of rainfall followed by a six month dry period.

The November-December 2007 drought that adversely affected Guangxi Province and some 200,000 hectares of farmland in Guangdong Province caused water levels to fall to no more than one meter in the Beijiang, Xijiang, and Dongjiang stranding vessels in the shoals. Safe drinking water supplies became sparse and crops died. Similar droughts are recorded in this area, and now, the farmers are faced with global climate change that may lengthen or increase drought severity. Thus, water management becomes critical for successful crop production even where the annual rainfall may reach six feet (2 meters).

In the degraded lands of tropical monsoon South China, farmers generally plant crops during the April – September rainy season of 52-73 inches (1300-1825 mm) to assure adequate crop development before the October – March dry season sets in. Dry-season rainfall averages about 12 inches (300 mm) but in some particularly dry years rainfall may only reach five or six inches (125-150 mm) during the dry period. The dry season reduces soil moisture, ground-water recharge, and the amount of water available for irrigation and, as a consequence, the flow of springs and small streams slows or stops.

What sort of an agricultural system might withstand such conditions and yet provide the small farmer with an adequate income? This paper proposes an agro-ecological intercrop system that may have potential to assist the farmer particularly in times of drought. The inter-cropped combination of pineapples, pomegranate trees, and caper bushes, as yet untested, may be worthy of consideration. First, let’s examine these three crops to identify the useful properties that each might possess that could help the crops of the small farmers survive over the long, dry season, help the farmer improve his/her water resources and agro-ecological conditions, as well as provide economic opportunities.

Pineapple: The pineapple (Ananas comosus), first grown in China in 1594 (Morton, 1987a), is not a stranger to many South China farmers. In fact, China is one of the world’s top pineapple producers. The pineapple’s original home is thought to be southern Brazil (Ekern, 1965), or more specifically in the Parana-Paraguay Basin (FAO AGL, 2002). Although a valuable farm crop in its own right, it also has important water-conserving characteristics that can alleviate water-shortage problems.

The pineapple plant is highly effective at collecting rain water and moisture from fog and mists. The leaves transpire at night when it is cool rather than during warmer day-time temperatures (FAO AGL, 2002) and, thus, only a small amount of water is lost to transpiration. For example, the water loss/cm2 of leaf-surface/hr is 0.3-0.5 mg for the pineapple whereas the value for the tomato is 4.7-6.5 and tobacco 6.7-9.3 (Bailey et al., 1951), corn is 26 mg, the cockle burr 43 mg (Ekern, 1965). A relative humidity (RH) of 50 – 90 percent is preferable for the plant’s growth, conditions much like those of Guangdong Province where the average annual RH is 79 percent. Pineapple will produce fruit at rainfall levels as low as 25 inches – 150/year (625 – 3750 mm/year) (Morton, 1987).

The pineapple is able to withstand completely dry periods for as long as three months (FAO AGL, 2002). The undersurface of the pineapple leaf is covered with unique plant cells called “trichomes” (Goff, 2003; Ekern, 1965) that are highly effective at collecting water from rain, fog, and mist and transferring some of the water into the pineapple leaf. Where fog and mists exist, transpiration is dramatically suppressed due to the elimination of the atmospheric vapor-pressure deficit. Water collected this way by the pineapple can enhance ground-water recharge. In addition, the greater yearly frequency of local fogs and mists helps the pineapple offset the negative effects of drought periods.

Because of the pineapple’s effectiveness at suppressing transpiration and its ability to collect water, it is able to contribute significant amounts of water to ground-water recharge (Ekern, 1965). A large amount of recharge, for example, occurs in non-irrigated pineapple fields above Pearl Harbor, Hawaii (Giambelluca et al., 1996) Here, ground-water recharge minus pineapple water-use is about 30 inches/yr (750 mm/yr). The evapotranspiration (ET) for the pineapple plant is 28 – 40 inches/yr(700 – 1000 mm/year) (FAO AGLW, 2002). The potential ET from sugar-cane fields and from areas covered by natural vegetation on the other hand is about five times as large as that from pineapple fields (Gingerich, 1999).

The pineapple plant prefers acid (pH 4.5-6.5 but not above pH 7.0), well-drained soils like those of the deeply weathered granites of South China, and it tolerates low-fertility soils and soils with high levels of soluble aluminum and manganese (Bartholomew et al., 2002). The planting density of pineapple monocultures commonly is 17,400 – 20,250 plants/acre (43,000 – 50,000 plants/ha) (Ekern, 1965; FAO AGLW, 2002). The weight of the leaves alone from such plantings can reach 40 tons/acre (100 tons/ha) that can be used for ruminant feed (Gepts, 2005). The leaves probably could be used also for farm-level biogas production.

Pomegranate: Long ago, the pomegranate (Punica granatum) was introduced into China from Persia and the plant grows successfully even in South China. The pomegranate is small deciduous tree or shrub, which grows to a height of 20-30 feet (7-10 m), and lives as long as 200 years. The tree requires about 10-20 inches (250 mm-500 mm) of rainfall annually, is extremely drought tolerant, and can tolerate brackish-water irrigation and low-nutrient soils. The fruit is equal to the apple in having a long storage life (Morton, 1987b). The tree can be easily pruned to a bush-size height of about 6-12 feet (2-4 m) (www.desert-tropicals.com), begins fruiting at 2.5-3.0 years, and is insect pollinated. The pomegranate likes a well-drained soil, a sunny site, and tolerates acid and alkaline soils. Its roots penetrate the soils at least three feet and perhaps further in sandy or light soil (J.Kartesz, 2007, per. comm.) In addition, pomegranate is a valuable hardwood (Jim, C.Y., 1990). The pomegranate fruit has a diameter of 2.5-5.0 inches (60-125 mm) and it ripens about 6-7 months after producing orange-red flowers in spring and early summer. Its many, small seeds make up 52 percent of the fruit’s weight. The rind and flowers are used as dyes and the bark is used in Japan to make an insecticide (Morton, 1987b).

Today, the pomegranate has become increasingly popular in the West and is used in a wide variety of fruit-based beverages and food flavorings (Barrett, 1/23/06). The pomegranate’s high anti-oxidant juice has attracted considerable attention in the last few years from industries that produce foods for a growing health-conscience society.

Caper: The caper plant (Capparis spinosa) is a spiny shrub about one meter tall historically grown in the Mediterranean region requiring only 8-27 inches/yr (200-680 mm/yr) of water. Capparis spinosa, var.Mariana (now subsumed under Capparis cordifolia Lam), grows in high rainfall localities (+80 in; 2000 mm) like Guam, the Solomon Islands, Vanuatu, the Philippine Islands, Indonesia, and Queensland, Australia (http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?8897 ) where acid soils are common.

The caper plant produces flower buds that when pickled in vinegar or preserved in salt are used to provide a unique spicy mustard- or pepper flavor to food (Alkire, 1998). The hand-picked caper berry or bud, varies in size from less than 7 mm to about 14 mm. The plant grows low to the ground and spreads out laterally into a general circular form

The plant has the ability to fix nitrogen. The caper’s mature roots reach depths as great as 60 feet (20 m) (Fairuchina, 1974), grows in low-nutrient, gravelly soils, is effective at controlling soil erosion, withstands strong winds, and is arranged at 325-400 plants/acre (800-1000 plants/ha) in monoculture plantings (www.rirdc.gov.au/NewCrops; www.australiancapers.com.au). The especially long roots offer a uniquely deep space for carbon storage. Because the caper can be pickled easily, refrigeration is not needed on the farm to preserve the buds.

Today, in various parts of the world such as Australia (www.rirdc.gov.au/reports), the caper is gaining in popularity as a new crop. Like the pineapple, the caper acts as a retardant of wild fires. It has a life expectancy of 25-30 years. The caper plant is unusually hardy and is able to grow even in cracks high on rock walls in dry areas of North Africa. It grows even in cracks in the Colosseum walls in Rome, Italy where the rainfall is at least 30 in/yr (750 mm/yr).

Pineapple-caper-pomegranate intercrop potential benefits: Knowing that pineapple plantings benefit ground-water recharge significantly, how might we take advantage of the pineapples’ sparse water use and effective ability to recharge groundwater to benefit South China’s small farms, as well as improve their degraded lands? How might we reduce soil erosion from pineapple fields using this crop combination? What would be some environmental and economic benefits of such an intercropped system?

South China has a tropical monsoon climate with roughly a six-month wet season and a six-month dry season. Because the pineapple, pomegranate, and caper plant require low amounts of water for survival, the intercrop of the three plants would likely withstand South China’s two contrasting seasons. Farm-style propagation of the three crops involves standard techniques. All three crops could be planted at the beginning of the six-month wet season allowing them time to establish before the onset of the six-month dry season.

Water collected by the pineapple plant that is contributed to ground-water recharge could help supply the water needs of the deep-rooted caper plant and the shallower-rooted pomegranate tree and still contribute significantly to ground-water recharge overall. The small amount of water extracted from the soil by the pineapple comes mostly from the soil’s top 10-20 inches (30 cm) (Ekern, P.C., 1965). Thus, the pineapple’s sparse use of water would compete little for the water needs of the pomegranate whose roots penetrate the soil to depths of about 3 feet (1 m) (J. Kartesz, 2007, per. comm..) and those of the caper plant whose roots may reach 60 feet (20 m) (Fairushina, 1974).

Ground-water recharge beneath a pineapple field ultimately could increase soil moisture, raise the water table and lead to reestablish of local stream-flow. The reestablishment of stream flow as the groundwater table rises would offer the farmer additional growing sites as spring flow returned. The farmer might plant these sites with some medicinal plants for sale locally. Cheung (1983-1986) describes 400 medicinal herbs that grow in Hong Kong and his descriptions of the preferred habitats indicate that about 10-15 percent of these medicinal plants would grow in the wet soils around springs and near small streams.

If the caper plant were inter-planted with the pineapple and pomegranate, the caper could help contribute to an increase in soil moisture; reduce soil erosion; lower soil temperatures; and help to increase soil-organic matter. The caper plant is able to fix nitrogen (Andrade et al., 1997), a likely benefit to the other plants. Because the caper plant and the pomegranate tree have long lives, they even would help sequester atmospheric carbon for extended periods and thus would contribute positively to a reduction in green-house gases. The deep roots of the caper would allow carbon to be fixed to depths as great as 60 feet (20 meters).

The pineapple (Heanley, C.M, 1935) and the caper plant (Austral. Caper Co.) retard the movement of wild fires, a phenomenon common during the dry season on South China’s grass-covered, degraded, hilly lands. Wildfire retardation also would help protect the inter-planted pomegranate trees. In addition, the pineapple and caper plants grow low to the ground so that their likelihood of survival of South China typhoons seems good. Pruning the pomegranate to a bushy configuration would make fruit harvesting easier for the farmer and would help increase the plant’s survival under strong typhoon winds.

All three crops – pineapples, pomegranate, and caper — are at least somewhat salt tolerant thus expanding their planting sites to coastal and island sites. The pineapple is considered moderately tolerant to sea water, the pomegranate moderately sensitive (Maas, 1993), and the caper plant can grow along the shore within the zone of sea-water spray (Alkire, 1998).

The farmer could benefit economically from such a crop mix. In addition to the fruit, the pineapple plant produces abundant leaves that can be used for ruminant feed (Gepts, P., 2005) and for farm-level biogas production. The three plants could provide the small farmer with varied sources of income. For example, a potential market for the sale of capers exists in China’s large cities where Chinese affluence is increasing and foreign tourism is high and growing. Pineapples and pomegranates already are familiar to the Chinese public however the popularity of the pomegranate has grown rapidly in recent years because of its recognized health values. However, early market research on the three crops is essential. The Australian market research associated with their efforts to grow the capers commercially is worth examining http://www.rirdc.gov.au/reports/NPP/05-132.pdf.

This proposed agro-ecological system is intended for use on deeply-weathered granite (saprolite), degraded, hilly sites so common in South China. Generally this is the farmer’s poorest land. Thus, using the degraded land for the proposed inter-crop system would not compete for the farmer’s best agricultural lands.

A field study is essential to assess the water-use balance for the pineapple-pomegranate-caper system before attempting to extend the system to the farmer. Further, the geometry and spacing of the three plants must be worked out so as to benefit the small farmer economically and to provide for the maximum ecological benefit. Pineapples, for example, might predominate in the first year or so of planting to assure the greatest impact on ground-water recharge and the soil environment as the pomegranate and caper plants became established. The farmer might wish to alter the mix of the three crops depending on the stage of the site’s environmental improvement, and on the farmer’s best economic opportunities.

All three of these plants are non-native to China even though the pineapple and pomegranate have adapted well to China historically. How well the caper would adjust to this new ecological setting is not know at this time. The Heshan Hilly Land Interdisciplinary Experimental Station, CAS, Guangdong Province, (http://www.scib.ac.cn/hsz/English/index.htm), a part of the South China Institute of Botany, has agreed to test the growth of caper seeds on degraded sites of deeply weathered granite. Seeds have been provided by (1) the University of Guam, and (2) the Eremophytes Botanic Garden, CAS, Turpan, Xinjiang, China (http://www.bgci.org/garden.php?id=1396). The seeds from Turpan’s desert environment are Capparis spinosa, and those from Guam are Capparis cordifolia Lam which grow in deeply weathered volcanic clay.

Summary: The system is a blend of agroecological thinking and a concern for the small farmers’ economic wellbeing. The system is built around the pineapple because of its pronounced ability to recharge groundwater. It is possible that there are other crops that could adapt to the six-month arid period that might be incorporated into this system or that might be substituted effectively for the pomegranate and caper.

The suggested pineapple-pomegranate-caper intercrop system as envisioned here has the potential to do the following for the local environment: increase ground-water recharge significantly; reestablish perennial stream-flow; increase soil moisture; reduce soil erosion; lower soil temperatures; and increase soil-organic matter; fix nitrogen; trap carbon in soils to depths of 60 feet (20 meters); retard wildfires; and minimize crop losses from typhoons. In addition, during dry periods or extended drought conditions, the system has low water needs and would not be easily affected by exposure to salt water. As for the farmers’ economic well being, the system could: provide ruminant feed; serve as a source of organic matter for bio-gas production; provide varied crops for different sources of income, and yet not compete for use of the farmer’s best land.

References cited:

Alkire, B., 1998, Capers, Purdue University, Center for New Crops and Plant Products, http://www.hort.purdue.edu/newcrop/CropFactSheets/caper.html.

Andrade, G., Esteban, E., Velasco, L., Lotite, M.J., and Bedmar, E.J., 1997, Isolation and identification of N_2-fixing microorganisms from the rhizosphere of Capparis spinosa (L.), (abst.), Plant and Soil, v. 197, no. 1, p. 19-23.

Australian Caper Company: www.australiancapers.com.au., (accessed 7/08/08).

Bailey, L.F., Rothacher, I.S., and Cummings, W.H., 1951, A critical study of the cobalt chloride method of measuring transpiration; Plant Physiology, p. 563-574.

Barrett, J., 2006, Jan. 23, Trends: join the fruit club; Newsweek, p. 10.

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Giambelluca, T.W., Ridley, M.A., and Nullet, M.A., 1996, Water balance, climate change and land-use planning in the Pearl Harbor Basin, Hawaii; Water Resources Devel., v. 12, no. 4, p. 515-530.

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