| Livestock Research for Rural Development 9 (4) 1997 | Citation of this paper |
Goat and Rabbit Research Centre, SonTay, Hatay, Vietnam
Finca Ecologica, University of Agriculture and Forestry, Thu Duc District, Ho Chi Minh
City, Vietnam
Three treatments were compared: planting at monthly intervals from June 1994 through to May 1995; mulching or no mulching with the dead leaves; and organic (cattle) manure or chemical fertilizer. The experimental design employed monthly planting as main plots, mulching or no mulching as split plots and fertilizer type as split-split plots.
This paper summarises results for the second harvest which was done 12 months after the first harvest. Fertilizer treatments and management were the same as in the first year. The two fertilizer regimes were: organic (from cattle) manure (20 tonnes/ha) or chemical fertilizers (150 N as urea, 100 P205, 200 K20 kg/ha) as control. Mulching consisted of detaching the dead leaves and leaving them on the soil surface or removing them from the plot at monthly intervals beginning 6 months after the previous harvest. The urea was given in three applications (at 1 month, 3 months and 5 months after first harvest). Phosphorus was supplied after harvest. Manure and potassium were in two dressings (75% after harvest and 25% 5 months later). The planting material was stem cuttings (30 cm length) in two continuous rows per furrow.
Overall populations decreased from the first to the second year. There was a strong indication (P=0.06) that the manure treatment supported a higher plant population than the chemical fertilizers. The yield of edible biomass (stalks, tops and green leaves) which can be used for feeding animals was higher in the second than in the first year, probably because of the better climatic conditions for plant growth. The pattern of yield was similar in both years with highest yields for plots established in the traditional season (January-July). Mulching increased yield by 8% in the first harvest and by 15% in the second harvest. It is concluded that year-round planting of sugar cane, although not recommended for sucrose prooduction, is nevertheless feasible when the crop is to be used as livestock feed.
Sugar cane has the twin characteristics of year-round growth but a harvest capability that is often seasonally constrained in order to optimize sucrose yield both in the field and during the process of extraction. For energy, animal feed and protection of soil ecosystems, sucrose yield is less important than a year-round, stabilized supply of total biomass.
An experiment to investigate the response of sugar cane planted in each of 12 consecutive months was established in the Goat and Rabbit Research Centre in July 1994. Mulching with the dead leaves, or not, and organic manure or chemical fertilizer, were the other treatments. The results for the first harvest year (Nguyen Thi Mui et al 1996b) showed that stalk yields were higher (67-74 tonnes/ha) for plots established between January and July than for those planted from August to December (37-50 tonnes/ha). Brix varied markedly with planting date and was highest for cane planted (and harvested) in the period from October to April. Mulching increased stalk yield by 14% but there was no difference between the types of fertilizer.
This paper gives the results for the second harvest year (1996-97).
The experiment was established on a semi-acid (pH = 4.2 - 4.3), medium clay (35%) soil in the upland area of Bavi district. The three treatments were:
The experimental design employed monthly planting as main plots, mulching or no mulching as split plots and fertilizer type as split-split plots.
Sugar cane plots (1,000m) were planted every month at 90 cm row distance using the local variety (POJ 30-16). The two fertilizer regimes were: organic (from cattle) manure (20 tonnes/ha) or chemical fertilizers (150 N as urea, 100 P205, 200 K20 kg/ha) as control. Mulching consisted of detaching the dead leaves and leaving them on the soil surface or removing them from the plot The urea was given in three applications (at 1 month, 3 months and 5 months after planting). Phosphorus was supplied at planting. Manure and potassium were in two dressings (75% at planting and 25% at 5 months). The planting material was stem cuttings (30 cm length) in two continuous rows per furrow. Other management practices, such as the method of fertilizer application, cultural practices and use of pesticide, were carried out according to the traditional practices of the farmers. For the ratoon crop the same amounts of fertilizer were applied one month after each plot was harvested.
The plots were harvested monthly after 12 months of re-growth. The whole plant was harvested by cutting the stalk at ground level. The stalk was separated from the whole plant by cutting immediately below the second node measured from the top. The growing points (tops) were then separated from the leaf blades (green leaf). Each component was weighed at the time of harvesting.
Samples of the stalk from each plot (about 10 kg) were crushed by passing them three times through a 2-roll mill driven by a buffalo. On the second and third pass the partially pressed stalks were doubled to maximise extraction of the juice. Extraction rate was expressed as weight of juice as a percentage of the weight of cane stalks. The total soluble solids in the juice (Brix) were determined using a hand refractometer.
Soil samples were taken at 0-20cm depth from each experimental plot immediately after each harvest. Equal amounts (3 kg) were put into clay pots (about 5 litre capacity) for a biological test of overall soil fertility. Three seeds of maize were planted. 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 average temperature and monthly rainfall in the Bavi area for 1995-97 are indicated in Figure 1. The periods of low average temperature (15-19C) were concentrated from December to March. Rainfall was also low (2.2-67 mm/month) from November to April.
The numbers of plants/m for the different treatments during each of the two years are
shown in Table 1. Overall populations decreased significantly from the first to the second
year. There was a strong indication (P=0.06) that the manure treatment supported a higher
plant population than the chemical fertilizers.
The yield of edible biomass (stalks, tops and green leaves) which can be used for
feeding animals was higher in the second than in the first year, probably because of the
better climatic conditions for plant growth (Table 2). The pattern of yield was similar in
both years with highest yields for plots established in the traditional season
(January-July).
Mulching with dead leaves significantly increased the biomass yield and the increase was
greater in the second year (15%) than in the first year (8%). The beneficial effect of
mulching on yield is in agreement with our earlier reports (Nguyen Thi Mui et al
1996a,b;1997a,b) and the increasing effect with successive harvests is similar to the
finding of Nguyen Thi Mui et al (1996a).
The use of organic manure rather than chemical fertilizer tended to enhance biomass yield but the effect was small (3-5% increase).
The data for juice extraction rate and Brix of the juice are shown in Table 3 and
Figure 2. Both criteria varied with month of planting with a tendency for extraction rate
to be highest when the Brix was lowest. We have no explanation for the increase in
extraction rate due to mulching and use of organic manure in the second harvest.
The effects of treatments on overall soil fertility as measured by the growth of maize
in soil samples from the experimental area are shown in Table 4. In both harvest years
soil from mulched plots and plots receiving organic manure supported better growth of the
maize indicating positive effects of these treatments on soil fertility.
The results of the second year of growth of sugar cane established in different months
confirm those observed in year 1, namely that the traditional planting season (January to
May) results in higher yields of sugar cane containing juice with higher concentrations of
sugars. Both yield and sugar content are important when sugar cane is grown to produce
crystalline sugar. For livestock feeding, however, it is important to have sugar cane
available throughout the year even if the nutritive value is slightly inferior (Nguyen The
Mui 1996c, 1997a). This experiment shows that year-round planting is feasible as a means
of providing a regular supply of cane for livestock feeding.
A reviewer has made the point that it would have been useful to have had details of the
composition of the organic manure and of the way it was incorporated in the soil. The
senior author has been asked to provide this information and/or to comment.
This research was supported by the International Foundation for Science through a grant
(B/2291-1) to the senior author.
Nguyen Thi Mui, Preston T R, Dinh van Binh, Le Viet Ly and Ohlsson I 1996a Effect of management practices on yield and quality of sugar cane and on soil fertility. Livestock Research for Rural Development. Volume 8, Number 3:51-60
Nguyen Thi Mui, Dinh van Binh and Preston T R 1996b Effect of planting season and type of fertilizer on biomass yield and quality of sugar cane. Livestock Research for Rural Development. Volume 8, Number 4: 13-18
Nguyen Thi Mui, Dinh van Binh and Preston T R 1996c Nutritive value for pigs of juice from sugar cane planted at monthly intervals throughout the year. Livestock Research for Rural Development. Volume 8, Number 4: 24-29
Nguyen Thi Mui, Preston T R, Dinh van Binh and Ohlsson I 1997a Responses of four varieties of sugar cane to planting distance and mulching. Livestock Research for Rural Development. Volume 9, Number 3: 69-77
Nguyen Thi Mui, Dinh van Binh and Preston T R 1997b On-farm evaluation of planting distance and mulching in sugar cane. Livestock Research for Rural Development. Volume 9, Number 3: 78-82
Nguyen Thi Mui, Dinh van Binh and Preston T R 1997c Sugar
cane tops as a feed for goats; effect of harvest season. Livestock Research for Rural
Development. Volume 9, Number 1: 25-28
Received 1 August 1997