Goat and Rabbit Research Centre, SonTay, Hatay, Vietnam
* Finca Ecologica, College of Agriculture and Forestry, University of Ho Chi Minh city, Thu Duc,
Ho Chi Minh City, Vietnam
A trial was conducted on 10 farms in Bavi district, Hatay province in North Vietnam. The results presented for the first year showed that returning the dead leaves to the soil in a range of household plots (n=10) increased stalk yield by 8 tonnes/ha (10.6%) over the control and improved soil fertility. There was no change in juice quality (Brix) or extraction rate. Narrowing the row distance from the traditional 150cm to 100cm increased stalk yield by 20.4 tonnes/ha (29.4%) with no changes in the quality (Brix) of the juice for animal feed or the rate of extraction in a simple 3-roll mill.
Bavi district, which is adjacent to the Goat and Rabbit Research Centre (GRRC), is a mountainous area in Hatay province in North Vietnam. Annual rainfall is around 1,850 mm and the average temperature about 23o C. Agriculture, including forestry, is the main activity. Cassava is the most important food crop because it substitutes for rice as a staple when rice is not available. The cassava plant is also a source of animal feed, especially the leaves. The second major crop is sugar cane which is mainly sold in local markets for chewing and juice extraction. Some sugar cane is sold for processing in small artisan factories in nearby provinces. Most families also grow other field crops such as peanuts, soybeans, tea, sweet potatoes, bananas, oranges, papaya and jack fruit.
Almost all families keep livestock, with pigs, chickens, fish and ducks being the most common. Cattle and buffaloes are kept mainly for draught purposes, both for land preparation and transport. The productivity of livestock is low because inputs such as labour, feed and other investments are also low. Crop residues such as rice straw and maize stover play a dominant role as feed resources for these animals. They are generally supplemented by grass from the edges of roads, fields and ponds. In tree-cropping areas the most important feeds consist of leaves and branches. Being a mountainous area, the intensity of land use is not high and there is potential for growing more sugar cane provided a sufficiently attractive market can be developed. The use of sugar cane for livestock production could be a suitable alternative.
Research at the GRRC has shown the potential of sugar cane as a feed for pigs and goats. Many neighbouring farmers have shown interest in applying this technology which, according to Dinh Van Binh et al (1993), can provide them with a higher income than can be obtained from cassava. Ways of raising the productivity of sugar cane at farm level through improved agronomic practices thus have a high priority. The results of the on-station research described in the two previous papers (Nguyen Thi Mui et al 1996, 1997), where mulching and increased plant density led to higher yields and improved soil fertility, were considered to be the most appropriate interventions to introduce to local smallholder farmers.
In December 1994 ten farm households, located within 3-8 km of the centre, were selected for the study. Cropping systems, soil fertility and income in the households varied widely. Some farmers were already growing sugar cane in the hilly areas far from their houses. Others had planted sugar cane in their home gardens as an inter-crop with fruit trees. Management and fertilizer use varied from farm to farm but in each case the area used for the trials had previously been cultivated with cassava. The available land areas ranged from 500 to 1,200 m2. The same local variety of sugar cane was planted on each farm, but the amount and quality of the seed material, and the date of planting (between December 1994 and February 1995) varied accordng to the farmer's experience and income. Fertilization and control of diseases and weeds were left to the farmers' discretion.
The experimental treatments introduced on each farm were:
In the statistical analysis the different farms were considered as replicates. The mulching treatments were the main plots and planting distance the sub-plots. The plots were harvested 12 months after planting
The data recorded were: planting date, amount of fertilizer supplied, time for weed control, amounts of dead leaves, biomass yield and extraction rate and Brix content of the juice. For a biological test of soil fertility, soil samples at 0-20cm depth were taken immediately from experimental plots at each farm after harvesting. Equal amounts (3 kg) were put into clay pots (about 5 litre capacity) and three seeds of maize were planted in each pot. After 5 weeks the maize plants were removed from the soil, washed to remove soil from the roots and allowed to dry for 1 hour. The total fresh biomass and the roots were weighed.
The data were analysed by Analysis of Variance using the General Linear Model of the statistical software by Minitab (1993, Release 9.2). The differences between mean values of farms were tested using Tukey 's pairwise comparisons. Relationship between stalk yield of sugar cane and biological test of soil fertility (maize biomass from soil samples) was tested by regression .
Data for planting time, amount of fertilizers used and weed control are shown in Table
1. Planting time was different between farms. Amount of applied manure varied from 12-20
tonnes/ha and of urea fertilizer from 320-450 kg/ha (equal to 150-200 kg of N).
There was a significant reduction (P=0.001) in the number of times the mulching plots had to be weeded (2.7 times per year) compared with plots with no-mulching (3.2 times per year). There were significant differences among farms for all the parameters measured (Table 2). The stalk yield varied from 67 to 110 tonnes/ha (P=0.001), the tops from 14 to 30.3 tonnes/ha (P=0.001) and green leaves from 1.7 to 3.8 tonnes/ha (P=0.034). The total yield of edible byproducts (tops plus green leaves, commonly referred to in the literature as "tops"), varied from 15.7 to 31.8 tonnes/ha (P=0.001). The edible byproducts represented about 27.5% of the weight of the stalk (range of 20.4 to 40.9%; P=0.01). In Table 4 it can be seen that the rate of extraction of juice (kg juice from 100 kg stalk) varied from 43.3 to 49.7 (P=0.006) and the Brix of the juice from 20.6 to 22.4 (P=0.002).
Mulching increased the yield of the stalk (P=0.04), of the tops (P=0.05) and of the total edible byproduct (P=0.03) (Table 3), but did not affect juice extraction rate or the Brix of the juice (Table 4). These results are in agreement with those reported in the on-station experiment ( Nguyen et al 1996, 1997). Stalk yield increased by 8 tonnes/ha when dead leaves were left on the soil surface.. This has an opportunity price in the market of VND 3.2 million (about US$320.00), which exceeds by a factor of 2.3 the opportunity price of the dead leaves (28 tonnes/ha) as a source of fuel (about VND 50.00/kg). It is important to note that these results were obtained in the first harvest year. In the on-station trials the effect of mulching increased with successive ratoon crops (ie. 6, 20 and 30% improvements for the first, second and third year, respectively). The beneficial effects on farmers' plots of mulching with dead leaves of sugar cane are therefore likely to be even higher in the subsequent harvests.
Yields of stalk, tops, green leaves and edible by-products were all higher at the narrower row distance (P<0.002). Narrowing the row distance had no effect on juice extraction rate and Brix. These findings are also in agreement with those obtained in the on-station trials ( Nguyen Thi Mui et al 1996, 1997) and FAO (1994).
Results for the biological test of soil fertility are given in Table 5. There were differences in the biomass (P=0.03) and root yield (P=0.003) of maize plants grown on soil samples taken from the different sugar cane plots at farm level. In agreement with on-station findings, mulching increased both biomass (P=0.001) and root yield (P=0.001). There was no relationship between the biological test of soil fertility and the stalk biomass yield of the sugar cane (r=0.001). The reason may be that the differences in the soils between farms reflect a wide range of factors (eg: moisture availability; weed growth) and not simply the fertility of the upper 20cm of the soil (where the test samples were taken).
This paper was submitted in 1996 to the Swedish University of Agricultural Sciences in
partial fulfilment of the requirements for the Master of Science degree in
"Livestock-based Systems for Sustainable Use of Natural Renewable Resources".
Financial support from SAREC to participate in the Master's course is gratefully
Dinh Van Binh, Le Viet Ly; Nguyen Quang Suc and Preston T R 1993 Experiences of technology transfer of sustainable farming systems to the house hold sector in Bavi district. In: National seminar workshop on "Sustainable livestock Production on local feed resources" (Editors: T R Preston, B Ogle, Luu Trong Hieu and Le Viet Ly). UAF, HCM ciity: pp. 122-125.
Minitab 1992 Minitab Inc., 3081 Enterprise Drive, State College PA 16801-3008, USA,1993, Release 9.2.
Nguyen Thi Mui, Preston T R, Dinh Van Binh, Le Viet Ly and Ohlsson I 1996 Effect of management practices on yield and quality of sugar cane and soil fertility. Livestock Research for Rural Development. Volume 8, Number 3: 51-60
Nguyen Thi Mui, Preston T R and Ohlsson I 1997 Response of four varieties of sugar cane to planting distance and mulching. Livestock Research for Rural Development. Volume 9, Number 3: 69-77
FAO 1994 Trash for mulching in sugar cane. In Organic
Recycling in Asia and the Pacific. Regional office for Asia and the Pacific (RAPA). Food
and Agriculture Organization of the United Nationas, pp: 45-46.
Received 1 June 1997
Return to top