Sticking to the hillsides
Steep-sided, bare hills eroded almost to the bare rock and, in the dry season, not even enough grass to feed the livestock. It is a familiar sight in many parts of the world but, in Yunnan and Guangxi Provinces in southern China, a way has been found to reclaim the slopes for productive agriculture. Leading the recovery is pigeonpea (Cajanus cajan). This versatile, perennial, drought tolerant crop is being re-introduced to the region to rejuvenate the land, provide feed, fodder and fuelwood, and to host the natural resin producing lac insect, once widely grown until artificial resins killed the market for the natural product. But if nothing else grows on the hilly slopes, why should pigeonpea? And how do you establish a crop on steep, rocky ground? Chinese scientists, working with scientists from ICRISAT in India, believe they have some answers.
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| Credit:ICRISAT |
Pigeonpea has a very deep root system that can tap moisture from three metres below the surface. Once established, it maintains a tenacious hold even on steep, arid, wind-blown slopes. Getting it established is hard but the scientists found that if they scattered seed at very high density they could get reasonable success even if it meant that half the seed failed to grow. And if fewer plants survive, they compensate by growing larger. It is estimated that in Guangxi Province alone there are some 6.5 million hectares of currently wasted mountain slopes on which pigeonpea could be grown.
Pigeonpea varieties vary greatly in the time they take to reach maturity and in the size - and taste - of their leaves, pods and seeds. Which variety should be chosen for which purpose? The pigeonpea that became established in China, following its introduction some 1500 years ago by Indian traders, has small, bitter pods and peas. Although these long duration varieties are useful for soil conservation, they are not an attractive proposition for farmers who need feed and fodder that their livestock will accept. Sweeter tasting varieties, selected from the huge germplasm collection held at ICRISAT, have now been introduced and are so successful that the provincial government is promoting pigeonpea production in order to expand the livestock industry, while at the same time reducing the need to import feedstuffs. Trials have shown that about 52 tonnes per hectare of fresh fodder can be harvested in five cuttings and that the crop grows well during winter when normal fodder supply is limited. Cattle and goats can also graze on the standing crop whereas the grains are fed primarily to pigs and chickens. No ill effects have been observed and a ratio of meat mass to feed of 1:3.5 can be achieved by including pigeonpea in meal mixtures. After three to five years the crop should be re-sown. The old plants can be cut and used for fuelwood.
Faster growth - sweeter seed
Increasingly, pigeonpea is becoming acceptable for human consumption, thanks to the better seed quality and the greater convenience of shorter duration varieties. Green pods can be harvested as a vegetable and a variety of snacks are being developed for the market including spicy-crisp grains, noodles and a pigeonpea sweet paste that must otherwise be imported for producing the moon cake traditionally eaten at the annual mid-Autumn festival.
Although the market for lac collapsed when synthetic resins became widely available, lac production was once a major source of income for farmers in the southern provinces of China. Recent, renewed interest on the international market for naturally derived products could justify a return to lac production for which pigeonpea is ideally suited. Lac is the scarlet resinous secretion of Kerria lacca Kerr., a plant sucking insect of the Coccoidea family. Brood lac insects are bound on to the stem of one-year old pigeonpea plants just below the first branch. The larvae of the insect colonize the branches on which they secrete the gummy, resinous lac. The coated branches are harvested, twice a year. After crushing, sieving and washing, the resulting substance known as 'seedlac' can be further processed by heat or solvent extraction to produce shellac. In China, lac was used as a dye for leather until supplanted by synthetics. Shellac is used in industrial applications for surface coatings, textiles, wood treatment, printing, pharmaceuticals, adhesives and the electrical industry. Pigeonpea produces high yields - 750 kg per hectare of good quality lac.
From coating barren hillsides to coatings for high tech industries, pigeonpea promises to have a bright future as farmers and scientists work out more ways to make use of this versatile crop in dryland agriculture.
