3. INTEGRATED PRODUCTION PRACTICES OF CASHEW IN CHINA - Liu Kangde, Liang Shibang and Deng Suisheng[3]

1. INTRODUCTION

China has a cashew cultivation history of about 60 years. The total land area under cashew increased to 13,000 ha in 1979 and has since declined to the present 8,327 ha, which is mainly confined to the coastal areas of the south and southwest Hainan. The soils are poor and infertile in these areas with long dry spells in winter and spring and are generally considered unsuitable for the cultivation of other tropical food crops without irrigation. The cashew trees, however, grow well under such conditions.

The overwhelming majority of cashew trees in the orchards of Hainan are of seedling origin and hence low yielding. Some of the orchards have been forced to be abandoned due to poor management. Most of the orchards produce an average yield of around 212 kg/ha even if they have reached the age of maximum yield potential. The cashew nut has a low rating as a farm product and its contribution to the gross national product in economic terms is negligible.

It is only since 1977 that a research group led by Prof. Jiang Shibang of the Chinese Academy of Tropical Agricultural Sciences, successfully developed cashew budding techniques and launched a research programme on selection and breeding of high yielding clones as well as introduced rejuvenation practices for low yielding cashew plantations. Growing of cashew is at present listed in the poverty-alleviation programmes to be re-initiated as extension activities in the resource-poor coastal areas in the south and southwest areas of the Hainan island. In addition to its economic value as a crop, the cashew can be used in afforestation programmes to stabilize sandy coastal areas from erosion and help to bring about ecological benefits. Grant aid was given by the European Community for the development of the cashew industry from 1985-1990, through which systematic research was carried out on cashew production technology in Hainan island. These efforts have helped in promoting cashew production in Hainan. Current research is concentrating on breeding and selection of cold resistant clones/seedlings for different micro-climatic zones of North Hainan, Gejiu and Yingjian in Yunnan province.

2. CURRENT STATUS OF CASHEW PRODUCTION IN CHINA

2.1 Production Areas Under Cashew

Major cashew producing areas are distributed in the coastal areas of Ledong Lingshui, Dongfang and Sanya of Hainan Province. Scattered cultivations are also found in Wanning and Wenchang of Hainan and trial plantings in Xishuangbanna and Gejui in Yunnan Province. According to the 1996 statistics, the total area under cashew is estimated at 8,327 ha of which 5,780 ha are in production. Ledong county in Hainan has the largest area under the crop with 4,460 ha, accounting for 54 % of the national production followed by Changjiang, Dongfang and Lingshui, Hainan Province (Table 1).

Table 1. Cashew Production Statistics

Hainan Province				Ledong County			Dongfang
Year	Area (ha)	Harvest Extent (ha)	Production (tons)	Area (ha)	Harvest Extent (ha)	Production (tons)	Area (ha)	Harvest Extent (ha)	Production (tons)
1986	9127	-	819	4920	-	393	827	373	183
1987	9400	6027	712	4974	4174	415	580	307	36
1988	11,593	5993	632	5147	4140	369	1040	333	38
1989	10,427	-	863	4320	-	582	767	-	47
1990	9773	5273	552	4247	3607	258	780	310	45
1991	9667	5393	567	4320	3554	274	773	427	77
1992	9807	5327	608	4440	3627	258	927	393	129
1993	9613	5127	835	4307	3273	435	973	487	139
1994	9627	4767	918	4440	2887	500	1067	527	104
1995	8787	-	960	4454	-	498	1147	493	137
1996	8327	5780	1224	4460	3360	534	1187	633	353
Chanjiang County				Lingshui County			Sanyan City
1986	227	140	20	2433	-	214	240	-	7.3
1987	700	327	23	2553	1140	224	313	-	13
1988	2347	193	27	2360	1127	185	247	-	10
1989	2227	200	16	2347	-	181	260	-	24
1990	2200	207	15	2273	1007	174	253	-	60
1991	2133	207	16	2213	1040	107	160	-	82
1992	2167	213	21	2033	953	110	153	-	89
1993	2233	267	30	1893	887	113	140	-	93
1994	2073	300	87	1827	893	105	-	-	2
1995	1760	307	98	1207	-	100	133	-	101
1996	1360	967	149	1107	653	79	127	-	100

Source: Tropical Crops Division of the Agriculture Department of Hainan rovince, Bureaus of Statistics and Tropical Crops.

Cashew varieties grown in China belong only to the species of Anacardium occidentale L; eighteen types are classified according to color (red, yellow, variegated), shape (round, oblong, pyriform) of the cashew-apple and height (tall and dwarf), and these can be further classified into 54 types based on the size and shape of the nut.

Screening of cashew germplasm was initiated in the latter part of the 1970s, and 5 superior accessions of germplasm were accepted for national release in July 1990, which were introduced to the production system for commercial cultivation. The 5 selections are as follows:

• GA-63: Early flowering with medium nut size and a yield potential of kg/ha at the age of 5 years;
• HL2-13: Protracted flowering phase with medium nut size and a yield potential of 1332 kg/ha at the age of 5 years;
• HL2-21: Late flowering, dwarf in tree size, wind resistant with large nut size and a yield potential of 1341 kg/ha at the age of 5 years;
• FL-30: Long and extended full-bloom stage with large-sized nuts and a yield potential of 861 kg/ha at the age of 4 years;
• CP63-36: A selection with high percentage (63.7%) of perfect flowers, small nut size with a high yield potential of 21.1 kg/tree.

3. PROPAGATION AND PRODUCTION OF PLANTING MATERIAL

3.1 Nursery Establishment

There are no large scale State owned or private nurseries for cashew propagation in Hainan. Most cashew plantations have their own nurseries for production of planting material required for their expansion programmes. Sometimes, grower organizations set up their own nurseries in the vicinity of their cashew orchards specifically for the use of such ventures.

3.2 Planting Materials

Prior to 1978, all planting materials used were of seedling origin and only recently new orchards have been planted with superior grafted selections. In many areas seedlings continue to be used and nursery plants used are bare-rooted or established in polybags to facilitate transport. The practice of using grafted plants of improved selections started in the late 1980s.

3.3 Budding and Grafting Methods

Both patch-budding and side-grafting are practiced in cashew nurseries although the former method is more common. Side grafting is generally used for topworking and for breeding work on better performing clones.

4. ESTABLISHMENT OF CASHEW ORCHARDS

4.1 Land Preparation

Selection of cashew growing areas on Hainan island is primarily based on temperature criteria as low temperature regimes and cold waves in winter and spring are unsuitable for successful cashew production. In general, monthly mean temperatures should be above 20°C. Existing cashew orchards in Hainan are mostly located in the sandy loam and sandy areas of the coastal terrace at elevations below 100 m. Such lands with low agricultural potential are opened up by complete or strip ploughing. Lands with grass or shrubs are used by partial clearing and digging of pits for planting cashew. Most cashew plantations on the island have been established on flat terrain without any conservation measures.

4.2 Planting Season

Optimum planting season is during the early-mid wet season between June and September. The planting time however, is not so critical for polybag raised nursery plants, but when bare-rooted seedlings are planted in winter and spring the survival rate is low.

4.3 Spacing

Tree density is mainly dependent on varietal attributes of clones/seedlings and soil fertility conditions at a particular site. In general, tree density ranges from 120-270 trees/ha for seedlings and 105-150 trees/ha for clones. Most orchards follow the square planting system at a spacing of 6m x 6m. Closer planting gives higher yields at early bearing stage, and when canopies become dense orchards are thinned (7-8 years after planting).

4.4 Planting of Cashew

Pits are dug about one month prior to planting at a size of about 80 cm x 70 cm x 60 cm. Usually pits are dug by hand although mechanical digging has been introduced in recent times. After some exposure to sun, the pits are filled with top soil and organic manure before planting at the onset of the rainy season. When planting bare-root plants, the root system is spread within the pit before filling with soil. In the case of polybag raised plants, the root system is undisturbed and soil is re-filled and compacted layer by layer to ensure a firm substratum. Sufficient watering is provided immediately after planting and mulching is often practiced to conserve moisture.

5. MANAGEMENT AND AFTERCARE OF CASHEW ORCHARDS

5.1 Training and Pruning of Cashew

To achieve better fruit-set, young cashew trees are often trained to provide a better tree form. In the case of mature trees, pruning is carried out to eliminate overcrowding and shading or to remove weak, entangled, weak or dead branches infested with diseases or pests. Non-bearing wood is removed to promote vigorous growth of active branches that bear regularly. Training and pruning of mature trees is regularly carried out to remove excess wood.

5.2 Application of Manure and Fertilizer

Since cashew orchards on Hainan island are established in sandy soils that are relatively low in fertility, productivity is generally low unless manuring is applied to augment soil nutrients. Fertilizer application rates increase with age of orchard. Very little fertilizer is needed in the first year of planting as adequate basal fertilizer is given at planting. From then on, trees are manured/fertilized twice a year in July and September with 0.25 kg of urea in the second year when plants are about 40-50 cm high. In the third year, 0.5 kg of fertilizer is added. In the 4^th year 1 kg of fertilizer is added in two applications together with 0.5 kg of calcium phosphate, 0.3 kg of muriate of potash or 20-30 kg of organic manure for every application. The beneficial effect of P and K fertilizers were often enhanced by the addition of nitrogen fertilizers which seemed to have a direct effect on fruitfulness in cashew (Jiang Shibang et al).

5.3 Weeding and Mulching

Up to three years of age, young cashew trees need weed-free conditions around the base and 3-4 weeding cycles have to be carried out per year. Mulching is also practiced to keep the basal area weed-free and to maintain moisture and temperature balance in the upper layers of soil. Mulching is however, not essential for mature trees as the root system becomes extensive. Weeding is usually carried out by hand and occasionally when obnoxious weeds such as twitch-grass are present they are controlled with the use of glyphosate.

5.4 Cover-Cropping and Inter-Cropping

Natural grass and legume cover is usually maintained at time of land clearing to conserve soil and water since the trees are planted far apart. In young orchards cashew is also intercropped with green manure cover crops and/or short-term annual crops. Main cover-crops include Calopogonium mucunoides, Macrophyllum atropurpureius cv. Siratro, pasture grasses and inter-crops such as peanut, sweet potato and beans. In recent years, cashew is being inter-cropped in some areas with melons (watermelon and sweet melon) and vegetables such as hot pepper.

5.5 Supplementary Irrigation

Although cashew is generally established in the wet season in Hainan, a high survival rate is assured by resorting to supplementary irrigation within one month from planting. This practice becomes more necessary when inter-crops are taken but monocropped orchards and mature plantations do not receive any irrigation.

5.6 Plant Protection Practices

Cashew diseases are of minor importance in China. Root rot, stem rot and die-back may occur at the nursery stage while gummosis, defoliation and root rot have been observed in mature orchards. No serious attempt has been made to identify the causative organisms of these symptoms as these conditions did not seem to depress yields in any significant degree.

Pests on the other hand are economically important in cashew nut production. More than 40 insect pests attacking the stem, branches, leaves, tender shoots, flowers and fruit have been observed in Hainan plantations. The more serious pests are dotted-leg capsid (Hellopeltis fasciaticollis, Poppius), cashew fruit borer (Nephopteryx spp.) and green-hairy beetle (Plocaederus obesus, Gahan).

The dotted-leg capsid mainly infests tender shoots, racemes, leaves, cashew apples and young nuts at pre-inflorescence, blooming and young fruit stages. Population dynamics show that peak infestation occurs from February to March and its population declines after May. Based on these studies, infested trees are sprayed with pesticides at the early stage of infestation during November-January. Pesticides commonly used are 20 % fenfevarate with a dilution of 1 in 200, and a mixture of 40 % dimethoate and 80 % dichlorphos (1:2 ratio) with a dilution of 1 in 200 all given as a low volume spray.

The cashew fruit borer develops large populations during the fruiting season between March and June, mostly attacking the cashew apple, nuts, racemes and tender shoots. Chemical control is usually practiced in the mid-late March period when peak fruiting phase commences. Spraying of 20 % fenfevarate or 2.5 % deltamethrin (1 in 200 dilution) is usually carried out for effective control.

The green-hairy beetle attacks trunks and roots of trees. Topworked trees are particularly susceptible and cut-end coating and trunk whitewashing with a lime solution gives effective prophylactic control. Infested trunks are treated with 80 % dichlorphos (1 in 50 dilution) by injecting the chemical into caterpillar tunnels to kill larvae.

6. REPLANTING AND/OR REJUVENATION OF OLD TREES BY TOPWORKING

Cashew orchards in Hainan comprise mostly of unselected seedling trees often giving very low yields. Their level of management also leaves much to be desired. Detailed studies carried out by Jiang Shibang et al of the Chinese Academy of Tropical Agricultural Sciences since 1985 employing the horticultural practice of topworking with high yielding clones and a systematic fertilizer programme rejuvenated most of the uneconomical seedling orchards in Hainan. This is now an accepted practice among growers and a topworking program is now in progress.

7. HARVESTING AND PRODUCTIVITY OF CASHEW

Harvesting of cashew is carried out from March-June with peaks occuring in April and May. The flowering period lasts 2-3 months and hence the harvest period extends for 70-80 days. The cashew apple is hardly utilized for processing at present. Mature nuts are picked from the ground when ripe fruits drop naturally. Nuts are then collected and sun-dried before processing using a hand operated machine.

Cashew yields are usually low with maximum annual average yields reaching only about 212 kg/ha (1996 average) even in well managed orchards that have reached peak harvests, while about 30 percent of the orchards yield negligible harvests. Ledong county in Hainan has the largest area under cashew. These orchards have given an annual yield ranging from 71-173 kg/ha since 1990.

8. MARKETING

Cashew is a crop that is freely marketed in China. In general, cashew nut is purchased from growers by the State or private processing mills at prices as low as 6-7 yuan/kg of nuts which results in a low product output value and negligible profits for the growers. Cashew nut mills exploit this situation and even import unprocessed nuts from foreign sources for processing and re-export as well as trade in domestic markets. The cashew nut marketing system is poorly organized as there are no growers’ organizations to ensure fair prices to the producer. Many private companies exploit the situation and have their own marketing channels.

In the past, a major portion of the processed kernels was exported to Hongkong, reaching a maximum volume of 180 tons in 1994 (Table 2).

Table 2. Export of Cashew (kernels) from Hainan (in tons)

Year	1987	1988	1989	1990	1991	1992	1993	1994	1995	1996
Exports	97	139	-	159	19	-	21	180	-	-

Source: Hainan Statistical Year book 1995. Economics and Trade Department.

9. POTENTIAL FOR CASHEW NUT PRODUCTION DEVELOPMENT

Although there is some potential for cashew nut development, China does not have the optimum climatic regimes for expansion of the cashew industry. However, China has vast areas of land considered unsuitable for other crops and which can be judiciously exploited for expansion of the crop, considering the vast potential for consumption of the crop locally, and the possibility of government intervention to assist the industry. Expansion of the cashew crop has many socio-economic benefits. Marginal areas could be profitably farmed to assist resource-poor farmers and many areas with sandy soils could be environmentally stabilized by growing cashew. The coastal plain in south Hainan comprises of nearly 133,000 ha of upland suitable for cashew and other forest species of which about one third of the area can be brought under cashew. Since cashew cultivation does not require intensive production methods or high input costs, it is an ideal crop for impoverished areas. Introduction of high yielding clones and better quality varieties would undoubtedly benefit the producer as well as the processor and eventually benefit the consumer.

10. CONSTRAINTS IN CASHEW NUT PRODUCTION DEVELOPMENT

10.1 Climatic Limitations

Low temperatures and typhoons are two major climatic constraints affecting cashew production development in China. Geographical distribution of cashew is mainly restricted by prevailing low temperatures during winter and spring seasons of the year. Temperature is therefore, the prime factor in limiting the distribution of cashew. The south Hainan island which is situated at 18° north latitude with a mean minimum temperature above 19°C in the coldest month is considered suitable for successful cashew production where the crop flowers and fruits normally. In the north of the Hainan island where minimum temperatures go below 18°C, growth of the crop is somewhat erratic and restrained to various extents. It was found that cashew grows normally at a temperature range of 23-29°C, exhibits slow growth at or below 20°C and is restrained at around 18°C, whilst the trees suffer cold injury and succumb at 15°C or below.

Typhoons often damage cashew trees as the tree tends to spread and produce weak branches resulting in loss of the crop. Mild typhoon damage where only loss of foliage may occur, recovery can restore the crop within a few months.

10.2 Varietal Limitations

A large proportion of the cashew plantations on Hainan island comprise of unselected seedling trees which are low yielding and of poor quality. A survey of 1160 seven year old trees carried out in Ledong county showed that only three trees produced 7.5 kg of nuts per tree contributing only 0.26 %, while the rest gave an average yield of only 1.8 kg per tree (Shibang et al). Recent germplasm screening has yielded some superior clones which are now recommended for planting as grafts. Despite these attempts, productivity of cashew in Hainan remains low as compared to other crops.

10.3 Management and Aftercare

The majority of cashew orchards in Hainan are poorly managed especially at the juvenile stage. These receive very little attention and proper application of manure/fertilizer during the fruiting stage. Low yields experienced in most cashew plantations that have reached their peak bearing stage can be attributed to improper orchard fertilizer application practices. As a result, about one third of the plantations produce virtually no crop of any economic value and are in a neglected state. Fertilizer investigations carried out by Shibang et al showed significant gains from the application of nitrogen in combination with P and K fertilizer in low yielding orchards.

10.4 Pest Control Problems

Although pests such as dotted-leg capsid, cashew fruit borer and green hairy beetle have been identified and appropriate recommendations made, many growers fail to resort to timely spraying to alleviate this production constraint which has resulted in severe crop losses.

These constraints mentioned above are limiting production development of the cashew industry in China. Extension services have commenced a programme to improve the situation based on the research carried out by Shibang et al. Despite these efforts, cashew productivity remains low as orchards are maintained and managed with minimum inputs and efforts from growers.

11. CONCLUDING REMARKS

• Cashew production is mainly confined to the southern and south-western coastal areas of Hainan island. The majority of plantations have been established with unselected seedling germplasm which has resulted in low production and productivity. Cashew extents have progressively declined during the last 10 years.
• The Chinese Academy of Tropical Agricultural Sciences has conducted systematic research on agronomic practices and recommended rejuvenation techniques for low yielding orchards. These include topworking with high yielding clones and NPK fertilizer application to improve existing orchards.
• China has an enormous domestic demand for the cashew crop and local production has been unable to keep up with existing market requirements.
• Major constraints to cashew nut production development in China include climatic, varietal, and management problems including soil fertility maintenance and plant protection problems. Of these limitations, temperature appears to be the prime factor that limits geographical distribution of the cashew.
• Despite these climatic limitations, there is still scope for expansion of the crop to over 40 thousand ha along the coastal sandy tracts of Hainan island. Cashew can be therefore considered as a suitable economic venture for the resource-poor farming communities as well as an environmentally and ecologically stable crop for a sound land-use system for the coastal areas of Hainan Island.
• Cashew production will not assume any economic importance in the agricultural framework of the country unless a vigorous campaign is carried out to encourage and attract cashew growers through the offer of better varieties, supported by a strong research and extension effort to backstop the industry. It is only such a consolidated effort based on scientific management techniques that can assist farmers to increase production and productivity of the crop.