Murniati ([email protected]) and A. Ng. Gintings ([email protected])
Imperata cylindrica (L.) Beauv., a perennial grass, is one of the most notorious weeds in the world. It is commonly known as cogon grass, spear grass, blady grass, satintail and alang-alang. It is widely distributed in the tropics and subtropics.
The grass is very difficult to control or eradicate because of its excellent propagation system by abundant airborne seeds and vigorous rhizomes. It colonizes large areas with a wide variety of natural habitats such as desert dunes, wet lands, savannahs and forests, where it can inhibit the growth of other plant species and block ecosystems from further development.
Fortunately, the grass is intolerant to shade. Shading damages the grass by reducing its carbohydrate storage, its rhizome and tuber production, the dry weight of its shoots and by generally decreasing its vigor and/or regeneration capacity.
Nitrogen (N)-fixing cover crops, known as leguminous cover crops (LCCs), cast shade, reduce grass vitality and improve unfertile soils. They also establish a favorable microclimate, which enhances the activity of soil microorganisms. Nitrogen fixation rates for most legumes are in the range of 40 to 200 kg N/ha per year.
One such N-fixing cover crop is Pueraria javanica Benth., also known as Pueraria phaseoloides (Roxb.) Benth. and P. phaseoloides var. javianica (Benth.) Hook. Its common names are puero (Australia), tropical kudzu (in most of the tropics) and kacang ruji (Java, Indonesia). It is native to mainland Southeast Asia, particularly in Malaysia and Indonesia, and is now widespread throughout much of the wet tropics.
Peuraria javanica spreads, dominates the land cover and suppresses Imperata cylindrica, 10 months after planting.
An agroforestry system established on Imperata cylindrica grassland. Mahogany (Swietenia macrophylla) and sungkai (Peronema canescens) trees (18 months after planing); maize as an intercrop (3 weeks after planting) in East Kalimantan, Indonesia.
P. javanica has vigorous twinnings and climbing stems. It is a hairy perennial and is one of the best tropical legumes for smothering weeds. It can tolerate acidic soils and is suitable for soils with heavy or high clay content. The crop is also tolerant to flooding.
Suppressing Imperata grasses
The simple and cheapest method of suppressing grass is by "pressing the grass," where the grass is trampled against the ground or a weight is rolled over it. The weight kills the grasses in the lower layer. Only then can the seeds of the cover crop be sown. This way, P. javanica can dominate the land cover 10 to 12 months after planting. With its dense canopy, Pueraria javanica can suppress grass vitality. A field trial showed that once the cover crop dominated the land surface, Imperata cylindrica died. Some tree species could also be planted simultaneously with the cover crop - maize under mahogany (Swietenia macrophylla) and maize under sungkai (Peronema canescens). They could be established on I. cylindrica grasslands using P. javanica as a source of shade in suppressing the grass.
Roles in improving soil fertility
As the cover crop is able to fix nitrogen, it contributes to the nutrient supply of the other crops.
On an acid soil in Onne, Nigeria, P. javanica produced 2.2 Mg/ha (1 Mg = 1000 Kg) dry matter with a total N content of 60 kg/ha, 14 weeks after planting. Also on acid soils in East Kalimantan, Indonesia, it produced 7 Mg/ha dry matter, 12 months after planting. This biomass supplied important amounts of nutrients to the soil: 133 kg N, 11 kg phosphorus (P), 110 kg potassium (K), 13 kg calcium (Ca) and 21 kg magnesium (Mn). As a result, the nitrogen and carbon organic contents of the soils were significantly improved. The N content more than doubled, from 0.07 percent at the initial condition to 0.16 percent, after 24 months. The carbon content of the soil increased by 13 percent.
When compared with the biomass produced by N-fixing trees, P. javanica’s biomass was higher. The biomass productions of Gliricidia sepium, Leucaena leucocephala and Calliandra calothyrsus, grown in alley cropping systems in South Kalimantan, Indonesia, were 1.2, 1.8 and 3.7 Mg/ ha per year, respectively. These N-fixing trees were cut back three times a year to 50 cm above the ground. They required more labor than the herbaceous cover crop. The dense canopy of P. javanica also provided a favorable microclimate that allowed the development of N-fixing microorganisms and helped conserve the soil by reducing the surface flow of water in sloping areas.
Photos by Murniati. The authors can be contacted at the Forest and Nature Conservation Research and Development Centre, Jl Gunung Batu #5, PO Box 165, Bogor 16001 Indonesia.
Sumarhani and Sri Suharti ([email protected])
Taungya is a farming system commonly established in young teak (Tectona grandis) plantations of Indonesia. It is a short-period system (1-2 years), as it can not be sustained after the closure of the tree canopy. When this happens, the taungya system is unable to provide the daily food needs and livelihood of the people practicing it.
Since the closure of the tree canopy influences the continuation of this farming system, a new technology is needed to overcome or at least minimize obstacles in sustaining the system. Identifying shade-tolerant food crops is one alternative that can be investigated in order to extend the cultivation period of the taungya system.
In Indonesia, the taungya farmer mainly cultivates dry field paddy, as rice is the staple food in the country and its price is relatively stable. Thus, to study its performance, the shade-tolerant dry field paddy (known as the Jatiluhur variety) was planted under three-year-old teak stands with a 3 x 3 m spacing and a 40 percent shading intensity. Land preparation up to harvest time was observed from September 2000 to January 2001. The research location was at the teak plantation of the Perum Perhutani state forest enterprise at Jampang Kulon District, West Java.
The research site is situated at an altitude of approximately 100 m a.s.l. and its soil type is classified as Mediteran Complex and Litosol.
It has an average annual rainfall varying from 3 868 to 3 900 mm. Fifteen households participated in the project. Their average landholding ranged from 0.25 to 0.5 ha.
Characteristics of the Jatiluhur variety
The Jatiluhur variety can be cultivated in a monoculture system. It has a relatively short life span (100-115 days), but is relatively high-yielding (2.5-3.5 tonnes/ha). It is also relatively resistant to blast disease (Pyricularia oryzae), which is the main cause of decreased yields.
Land preparation
Low soil fertility, soil acidity and high concentration of iron (Fe), aluminium (Al) and manganese (Mn) are some of the main problems in cultivating food crops in a taungya farming system. Intensive land preparation and land burning to improve soil fertility do not fully solve the problem. Therefore, the minimum tillage technique and fertilization using green manure and calcium carbonate (CaCO3) are strongly recommended.
The minimum tillage system is meant to avoid destroying the lateral roots of the young stands. The paddy’s rooting system is not so deep as it only spreads on the ground surface.
Land is prepared at the end of the rainy season (August-September) and a green manure is applied as soil cover. The green manure increases the organic matter of the soil, improves the soil structure, reduces soil erosion, increases infiltration and maintains soil humidity.
Growing season
The dry field paddy does not need much water. However, the correct sowing time must be followed, especially on areas where the number of wet months is low (3-4 months). Following this procedure can produce up to 3 tonnes/ha. Paddy yield would decrease if planting was late or was done before the rains came.
If the time schedule for paddy cultivation is not well-planned, water shortage would affect paddy growth at the generative phase. The most suitable time for growing paddy is after the first rain of the year comes.
Planting methods
Three systems are commonly used for cultivating the dry field paddy. Each system has its own advantages and disadvantages.
The spreading system
Seeds are spread evenly on prepared land. Around 60-75 kg/ha of seeds are required. This is suitable for cultivating large areas of land with limited labor. However, there are two disadvantages to this system - it requires a large amount of seeds per surface area and the germination rate is low because the seeds are eaten by birds and rats, or are washed away by rain.
The tugal system
This system is usually applied on well-prepared areas and involves digging holes with 20 x 20 cm spacings. Two or three seeds are placed in each hole, and then covered with soil. This method requires approximately 30 kg of seeds per hectare.
The tugal is considered to be more efficient than the spreading system because it requires less seeds and the germination rate is higher. The disadvantage of this system is that it is more labor-intensive than the spreading system.
Strip planting
The system uses strips 2-3 cm deep with a 25-30 cm spacing. Holes are made within the strips, in which one or two seeds are planted and then covered with soil. This system requires 30-35 kg of seed per hectare. Like the tugal system, this system is also more efficient than the spreading system. It also allows for more optimal use of the sun and soil nutrients. Growing paddy in strips allows farmers to manage the seedlings better, making the dry field paddy grow uncluttered. Again, the disadvantage of this system is that it is relatively labor-intensive.
Plant management
For optimal production of paddy, the farmer must regularly weed and fertilize. Weeding must be done at two, four and eight week intervals after paddy planting. The following fertilizers are applied when planting: Urea at 50 kg/ha, TSP at 150 kg/ha and KCL at 100 kg/ha. Fertilizers are subsequently applied at 30 and 60 days after planting. Pest and disease control is also important. Chemical insecticides/pesticides are commonly used.
Harvesting and product processing
The average production of the Jatiluhur paddy under three-year-old teak stands is 2.72 tonnes/ha. Inappropriate harvesting and product processing methods can significantly reduce dry field paddy’s yield. A sickle or falling machine is used for harvesting.
Based on the study, the Jatiluhur variety promises to be a good alternative crop for planting under shady trees.
The authors can be contacted at the Forest and Nature Research and Development Centre, Jl Gunung Batu 5, PO Box 165, Bogor, 16001 Indonesia.
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"If you want to plant for a year, plant a cereal. If you want to plant for a decade, plant a fruit tree. If you want to plant for a century, plant a forest." - Chinese proverb |
A.S. Gill ([email protected])
The semi-arid subtropics cover large areas of north and central India. The main problem is the uncertain and uneven distribution of rainfall. The average annual rainfall is 900 mm. Moreover, the soil in these areas is unfertile, undulating and shallow, with a low water-holding capacity. Thus, agriculture in these areas is considered a high risk sector.
Under such harsh conditions, the main alternative is to adopt tree-crop farming under rainfed conditions. Trees, being perennial by nature, extend all possible assurance for the success of agriculture. Trees provide the five F’s: fodder, fuel, food, fruit and fiber. They are also known for their envrionmental service roles.
Considering the benefits from trees, the Indian Grassland and Fodder Research Institute in Jhansi, India, conducted a field experiment on a sandy loam soil of average fertility. The experiment involved four important trees of the region -- Albizia lebbeck, Azadirachta indica, Dalbergia sissoo and Acacia nilotica. The tree saplings were planted at a spacing of 6 x 12 m during the monsoon season of 1988. Chickpea was introduced in the winter season of 1999-2000 in the interspaces of the tree component. A control plot of the crop without trees was also established to compare the yield, with and without the tree component.
The trees were annually pruned to 50 percent of their height prior to sowing the horticultural crop in the interspaces. This was intended to provide sufficient light to the intercrops.
Data was collected over a three-year period (1999-2002). The chickpea control plot yielded an average of 12.92 quintal per hectare (q/ha, 1q=100 Kg). The data collected from the combined plots indicated that the highest average chickpea grain production was from the interspaces between Albizia (10.61 q/ha) followed by Dalbergia (10.29 q/ha), and Azadirachta (10.15 q/ha). It was the lowest from the interspaces of Acacia (9.72 q/ha). The relative grain yield for Albizia, Dalbergia, Azadirachta and Acacia was 82.1 percent, 79.6 percent, 78.5 percent and 75.2 percent, respectively.
Although chickpea yielded more when planted without the tree component at 12.92 q/ha (or 18% reduction in three years), the reduction was compensated by the benefits gained from the biomass production of the tree component.
The species easily adapts to a wide variety of environments, including diverse soil conditions, climates and altitudes. Normally, the tree produces abundant seeds, establishes itself easily and becomes very robust.
The author can be contacted at the Indian Grassland, Fodder and Agroforestry Research Institute, Jhansi (UP) - 284003 India.
Kun Zhang ([email protected])
Some say that forest management plays an important role in a Chinese farmer’s life. The author analyzed its statistical aspect.
Land area devoted to forestry
According to statistics at the Ministry of Agriculture, of the total land and water pond areas operated and managed by rural households, 27 percent are forestlands (Figure 1).
Expenditure in forestry
Figure 2 shows the composition of rural household expenditures. This figure indicates that forestry-related expenditures are too small to be registered, when compared with the other agricultural expenditures. During the last 20 years, a rural household’s forestry expenditure was highest at 0.78 percent in 1985 and lowest at 0.29 percent in 1997. After 1997, the proportion of forestry expenditure increased to 0.66 percent in 2000, but declined to 0.61 percent in 2001.
Labor force in forest management
At the national level, the average proportion of the labor force involved in forestry activities was around 2 percent in 1999. The proportion of the labor force in forest management among the eastern, middle and western regions of China varied. In the eastern and middle regions, about 2 percent was involved in forest management, the same as the national level. However, in the middle region, a slightly higher percentage worked in forestry than those in the eastern region. Western China had 1 percent of its labor force involved in forestry.
The forestry portion contributing to farmers’ income
From 1983 to 2001, the proportion of the forestry income of China’s rural household business showed a slowly decreasing trend (Figure 4). It was 1.61 percent in 1983 and 1.51 percent in 2001. The highest was 2.08 percent in 1985 and lowest at 0.33 percent in 1995. Although the income in forestry increased comparatively in 1996 and reached 1.57 percent in 2000, the income portion from forestry in the 1990s was markedly lower than that of the 1980s.
Conclusion
It is apparent that forestry-related activities do not currently play a significant role in China’s rural households, when compared to other agricultural activities.
Although rural households manage forestlands that are a third of the land area they work in, the net income from forest management has never reached more than 2.5 percent of their total net income. In addition, China’s rural households have put little effort and investment into forest management during the last 20 years.
However, it can be noted that forestry expenditure increased after 1998, reaching its third highest point in 20 years in 2000. It can be inferred that the environmental improvement campaigns such as the National Forest Protection Program, stimulated investment in forestry. After the big flood in 1998, the central and local governments began to focus on improving the environment. In the following years, more forestry projects were implemented, such as one to convert sloping farmlands into forestlands and grasslands. However, until 2001, forestry policies did not really motivate farmers to keep participating in forestry efforts.
The author can be contacted at the China National Forestry Economics and Development Research Center, 18 East Street, HePingLi, Dong Chen District, 100714 Beijing, China.
Figure 1. Composition of land-use by rural households in China, 1999.
(Source: National rural household sampling investigation, Ministry of Agriculture 2002)
Figure 2. Composition of household business expenditures, 1978 -2001.
(Source: China Yearbook-Rural Household Survey, China Statistics Press, 2002)
Figure 3. Distribution of rural households’ labor force, 1999.
(Source: National rural household sampling investigation, Ministry of Agriculture, 2002)
Figure 4. Percentage of forestry net income in total net income of rural household business, 1983-2001.
(Source: China Yearbook-Rural Household Survey China Statistics Press, 2002)
