Nutrient assessment of paddy weeds as ruminant feed in Java

N R Kumalasari, L Abdullah* and E Bergmeier

Department Vegetation and Phytodiversity Analysis, Albrecht-von-Haller Institute of Plant Sciences, Georg-August University of Göttingen,
Untere Karspüle 2, 37073 Göttingen, Germany
nurrkumala@gmail.com
* Department of Nutrition and Feed Technology, Faculty of Animal Science, Bogor Agricultural University (IPB),
Jl. Agatis Kampus IPB Darmaga, 16680, Bogor, Jawa Barat, Indonesia

Abstract

Paddy fields qualify as ruminant feed resources as they produce rice straw and weeds. The main objectives of the present study were to evaluate the productivity and nutrient potential of rice weeds as ruminant feed. The research was conducted in November 2011 and January 2012 in three lowland districts, Karawang, Brebes, and Gresik, and three upland districts, Cianjur, Karanganyar and Malang, on the island of Java, Indonesia. The weeds were collected in cultivated paddy fields, fallows and on paddy field bunds.

Weed biomass in upland areas was largest on bunds as a result of intensive weed control in paddy fields. In the lowlands most weed biomass was on fallows. Fresh weed biomass in the first rice growing season (after dry season) yielded 891–2369 g/m². Nutrient content revealed a proportion (% in DM) of crude protein between 12.6 and 17.9%, crude fiber between 34.1 and 42.2, and crude fat 0.8 and 1.2%. Thus, rice weeds have considerable potential as ruminant feed.

Keywords: biomass, fat, fallow field, fiber, Indonesia, protein, rice field

Introduction

On the island of Java, rice cultivation covers around 5.4 million hectares which equals more than 60% of the irrigated and intensive farming lands (Bappenas 2003). Weeds are frequently considered as one of the most hampering factors for rice production. Weeds compete with rice for sunlight, nutrients and water, thereby causing yield losses by about 10-50% (Nyarko and Datta 1993; Chin et al 2000). Weed management is needed to control weed populations and to reduce undesired effect of farming intensification. On the other hand, as paddy field areas produce rice straw and weeds, they may be important as ruminant feed resources.

Since the 1970s, the Indonesian government introduced herbicides as the main technique to control weeds on paddy fields. However, herbicide application may affect the weed community composition interrelated to crop productivity (Ulber 2010). Herbicide application contributes to reducing weeding labor but affects the environment and ecosystem balance, such as the water system, soil, and non-target organisms. It may cause phytotoxicity (Ueji and Inao 2001), fish toxicity and weed resistance to herbicides (Matsunaka 2001). Increased intensity of herbicide application has been identified as one of the major drivers for an unbalanced plant composition in paddy field vegetation and of biodiversity loss (Shibayama 2001).

A new approach to biodiversity-friendly management is therefore to enhance benefits derived from desirable weed species with high value for the farmer and the agroecosystem. The use of weed species is possibly the most efficient management to overcome problems of pollution through herbicide usage, weed decomposition or burning.

Morphology, phytomass and species composition of rice weeds vary enormously under different habitat conditions and land use (Soerjani et al. 1987). In traditional farming systems, farmers commonly used weeds as ruminant feed depending on weed properties. Some weeds may be grazed directly by ruminants, others may be cut, harvested and served as fresh feed in a cattle pen.

The feeding value of paddy field weeds is poorly studied and the considerable knowledge of local farmers remains to be recorded. As the knowledge of the nutrient value for most common tropical weeds, especially of their energy value and protein content, are only estimates, there is a lack of information. The main objectives of the present study were to evaluate the yield and nutrient potential of rice weeds that may serve as ruminant feed.

Materials and methods

Location

The research was conducted on the island of Java, Indonesia, on the territory of six districts, Karawang (33–53 m asl), Brebes (26–44 m asl), Gresik (14–41 m asl), Cianjur (527–856 m asl), Karanganyar (403–714 m asl) and Malang (526–684 m asl). Each district represented lowland (0–100 m) and upland areas (>400 m) of rice cultivation in Java. Suitable landscape sections of ca. 5 km x 5 km size were selected and 15 plots randomized therein.

Weed sampling

Sampling was done during the rainy season, October 2011 – January 2012. The weeds were collected in cultivated fields, fallows and bunds. Sampling was carried out to coincide with the traditional farming system in representing weeds from paddy field that supplied as ruminant feed. In suitable areas, 15 plots were selected, with each plot of 20 m2 in paddy fields and 10 m2 at bunds. The weed cover in paddy fields and bunds was determined by estimating the percentage of total weed cover. In the same plots, three subplots of 30 cm x 30 cm were randomly selected to assess weed biomass. Each weed species was identified and counted in the field. Unidentified plants were collected and identified in the laboratory/herbarium. All weeds in the subplots were harvested without soil, leaf litter and other contaminants using a sharp knife. The plant samples were individually weighed as fresh biomass and then mixed. The samples were dried at 60°C for 48 h, weighed as dry biomass and then prepared for nutrient analysis.

Nutrient analysis

The samples were analyzed in the Laboratory of Feed Nutrition, Department Nutrition and Feed Science, Faculty of Animal Science, Bogor Agricultural University. Nutrient analyses used proximate methods. Fiber content was analyzed using the method reported by Goering and Van Soest (1970) and nitrogen was determined by the Kjeldahl N method.

Results and discussion

Weed diversity and availability

The effect of the farming system on weed diversity and quantity is presented in Table 1. Farmers usually use herbicides or weed manually to control the weed populations in paddy fields. In upland areas continuous water supply throughout the year facilitated weed control and the amount of herbicides applied was reduced. Water supply is important as weed growth is distinctly decreased under flooded or submerged condition (Matsunaka 2001). In Senegal, flooding treatment brought about the same effect as herbicide application or manual weeding (de Vries et al 2010). In the Javanese lowlands, especially in urban areas such as Karawang and Gresik, labor for manual weeding is becoming increasingly scarce because a lot of textile factories and manufactures offer jobs with income amounts that are preferred by young people. Therefore the application of herbicides in the first tillage is widely practiced to kill all weeds that emerged in the time of fallow. The proportion of farmers who used herbicides on their farms was 60% or more in the lowland areas while less than 15% in the uplands (Table 1).

Water availability in lowland areas is limited during the dry season. In this period, farmers decide to let their land lie fallow or to plant intermediate crops such as corn, onions, beans, cassava and other drought-resistant plants. Rice cultivation is restricted to the rainy season. This practice influences the weed biomass source in paddy field areas. Weed biomass sources in upland areas were mostly bunds as a result of permanent control in the paddy fields. In contrast, in the lowlands the most important weed biomass sources were fallows (Table 1). Therefore, in upland areas, farmers usually harvest weeds from paddy fields to supply animal feed. In lowland areas, farmers usually take their animals to the fallows to let them graze until the afternoon, especially during the dry season.

The dominant weeds used for animal feed are listed in Table 2. It shows that farmer chiefly use grass for ruminant feed which is available on their land. About 15 grass species including Echinochloa spp., Panicum repens L., Cynodon dactylon (L.) Pers., Paspalum spp. and Brachiaria spp. were taken from paddy field areas for ruminant feed.

Previous studies reported that common weeds in the upland paddy fields in West Java were Myriophyllum aquaticum (Vell.) Verdc. and Sagittaria guayanensis Kunth, and in lowland areas Leersia hexandra Sw., Sacciolepis interrupta (Willd.) Stapf and Ipomoea aquatica Forssk. (Yakup 2007), while in central Java in lowland areas Marsilea crenulata Desv., Paspalum distichum L., Echinochloa crus-galli (L.) P.Beauv, Echinochloa glabrescens Munro ex Hook. f. and Fimbristylis miliacea (L.) Vahl were dominant weeds (Soerjandono 2005). The mismatches with our results may be due to the fact that the previous studies were restricted to paddy fields while our research covered paddy fields and bunds.

Weed biomass

Weed biomass is the most important indicator of feed availability for ruminants in paddy field areas. Weed biomass differed significantly among paddy field areas, with upland areas (Cianjur, Karanganyar and Malang) producing higher biomass values than lowland areas (Karawang, Brebes, Gresik) (Table 3). Fresh weed biomass in the first rice growing season (early rainy season) yielded 891-2369 g/m2. There were no significant differences between the locations of eastern, central, or western Java, respectively.

Fresh weed biomass in Javanese paddy fields differed from that found by Roder et al (1998) who measured 220-990 g/m2/year of fresh weed biomass over the rice growing season in northern Laos, or Baloch et al (2005) who measured 387-919 g/m² of dry weed biomass  in Pakistan. Our results show that the high values of fresh weed biomass have the potential to supply ruminant feed in Java. There are many factors affecting the weed biomass between countries, such as different species, seasonal and climatic variation as well as different farming management systems (Machado et al 2005; Baloch et al 2005). Weed biomass varies between regions and even between small farms in the same village due to differences of environmental factors and farming management (Roder et al 1998).

In the upland, there is natural water supply on paddy fields throughout the year. In the lowlands, most paddy fields were flooded only during the rainy season that begins in the end of September and lasts until March (Meteorology, Climatology and Geophysics Board 2008). These conditions lead to decreasing soil water content and increasing dry plant matter in lowland areas, especially towards the end of the dry season, because moisture stress might reduce plant growth but generally increases leaf to stem ratios (Linn and Martin 2012)

The combination of herbicide application and manual weeding in the lowland paddy fields of Karawang, Brebes and Gresik resulted in a significantly higher degree of weed suppression. Soerjandono (2005) reported that herbicide application in the early plantation time has the same effect in reducing the amount of weed as twice manual weeding. Manual weeding is a more effective method to reduce weed populations than herbicide application which might be related to their efficacy on weed, if labor is not a limiting factor (Baloch et al 2005). Herbicide effects on weeds include discoloration and deformation of leaves, growth inhibition and death (Ueji and Inao 2001). Daud (2008) reported that weeds from rice farming areas are safe for animal feed after about fourteen days after herbicide application.

Variability of surface water condition also affects the growth of rice weed communities (Juraimi et al 2011). Hence, weed biomass in upland areas is concentrated on terraced sites since weeds have been suppressed on about 70% of the paddy field areas through ponding waters. Paddy fields flooded with water until 10–15 cm depth has been found to be effective in the control of Echinochloa crus-galli and other weed species after the rice has been transplanted (Shibayama 2001). In all lowland areas, rice weeds were found to grow mainly in times of fallow and the values were not significantly different from each other.

There were biologically small but statistically significant differences in the comparison of dry matter percentage in each location. In the lowlands higher dry matter values were found than in the uplands. Cutting times and plant structural composition seems to affect weed biomass (Yolcu et al 2006).

Weed nutrient content

Weed nutrient content information is important for assessing the value of weeds as fodder for animals. In our study we found that their nutrient content qualifies weeds as ruminant feed (Table 4) Weed nutrient content can be affected by climatic conditions during growth and harvest, especially temperature, light and rainfall (Linn and Martin 2012). In hot climates weed will have a lower digestibility than weed growing in cooler climates even with identical crude protein contents (Mtui et al 2009).

Protein is the most limiting nutrient for ruminant productivity. Protein content of forage is influenced by species, relative maturity and the proportion of leaves (Ball et al 2005). In our study, the weeds examined were mostly young grasses harvested at about 25–30 days of age. The percentage of crude protein was found to range between 12.6 and 17.9% (Table 4), considerable amounts compared to that of native grasses (5 to 8%; ACIAR 2009) or to forage from a natural grassland in Poso, Java (6.31 to 6.63%; Damry 2009). This means that the crude protein content of the weeds in paddy field areas is sufficient for the maintenance of ruminants because our findings lie beyond a critical value of about 10% crude protein required for feed digestibility (Leng 1990).

The protein content is also affected by environmental factors such as season, area, sampling site (Miraglia et al 2008), water and soil nutrients (Sigua et al 2012). In Java, the crude protein content varied among locations, with the highest crude protein values in Cianjur and Brebes. The lowest crude protein content in Karawang may be due to the fact that a few sites in Karawang were studied in the dry season. Water supply affected crude protein content because grasses have less actively growing shoots and smaller proportion of leaves with higher stem to leaf ratios (Hughes et al 2011). Fertilizer application on paddy field could increase weed nutrient content. Sigua et al (2012) reported that flooding duration and level of fertilization have varied effects on crude protein.

Other weeds representing potential feed resources could be utilized to avoid protein deficiency which reduces the overall performance of the animals (Mtui et al 2009). Especially leguminous weeds, such as Centrosema spp. and Sesbania spp., may be used as protein supplement to counteract nitrogen deficiency of ruminant animals fed on poor quality feed. In this study, only farmers from Karanganyar and Gresik harvested leguminous weeds from their paddy fields as fodder for the animals, albeit in small proportion.

Crude fiber content was found equal in each plot, but neutral detergent fiber (NDF) and acid detergent fibre (ADF) content differed. NDF and ADF content in upland areas were higher than in lowland areas (Table 4). This could be a result of more rapid plant maturity causing lignification (Van Soest et al 1991) due to higher temperatures and severe moisture stress.

Acknowledgements

This paper is an output from field research carried out thanks to Erasmus Mundus Experts Asia (mobility program) and funded by BIOTROP (PhD grant 2012). We are grateful to Dr. Soekisman Tjitrosoedirdjo for useful comments on the proposal and Dr. Sri S Tjitrosoedirdjo for every support of our field work and laboratory research.

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Received 1 March 2014; Accepted 5 March 2014; Published 5 April 2014

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