Yield response of Elephant grass (Pennisetum purpureum) to guano organic fertilizer in the Highlands of Madagascar

V B Rahetlah, J M Randrianaivoarivony, B Andrianarisoa* and V L Ramalanjaona

FIFAMANOR (Centre de Développement Rural et de Recherche Appliquée), BP 198, Antsirabe 110, Madagascar
volats@yahoo.fr
* Laboratoire de Biotechnologie et Microbiologie, Faculté des Sciences, Université d’Antananarivo, BP 196, Antananarivo 101, Madagascar
blandine@andrianarisoa.net

Abstract

Dairy cattle farming is an important and expanding economical activity in the central Highlands of Madagascar. Elephant grass (Pennisetum purpureum) is by far the most cultivated forage grass due to its adaptation to zero-grazing systems and to a wide range of soil types including acidic.   A study was conducted at two sites located in the Vakinankaratra region, in the Highlands of Madagascar to assess the effect of locally available guano organic fertilizer on growth parameters, yield and forage quality of Elephant grass. A randomized complete block design with four replicates was used to compare 3 rates (300, 400, 500kg ha^-1) of guano organic fertilizer (4,8N-6,5P-1,2K) with one cattle manure rate (10t ha^-1) and one unfertilized control.  

Results averaged over the two sites showed that height and leaf length of Elephant grass at the first cut were higher under guano treatments as compared to the unfertilized control. Dry matter yield over two cuts increased by 43 to 57% and 39 to 54% under guano treatments as compared to control and manure treatment, respectively. Dry matter, total ash, crude fiber and crude protein contents were not different across treatments. Nitrogen uptake was 43 to 55% higher under guano rates compared with control. 

Key words: dairy farming, forage, growth parameters, nitrogen uptake, organic fertilizer, quality

Introduction

The farming systems in the Highlands of Madagascar are dominated by mixed crop-livestock farming systems. Dairy cattle farming under zero-grazing systems is an important and expanding economical activity in the central Highlands of Madagascar, specifically in the Vakinankaratra region which produces more than 80 percent of the national global milk production (Lecomte et al 2008). Improved dairy technologies including improved fodder crops production practices have led to the increase of milk production.  Dairy cattle in the region are mainly fed on natural pasture, cultivated fodders, crop residues and some concentrates. The limited holding size and the competition with food cropping have emphasized the need to rely on high-yielding fodder crops. Elephant grass (Pennisetum purpureum) is by far the most cultivated forage grass. It is well adapted to a wide range of soil types including acidic but yield potential is correlated to soil nutrient status (FIFAMANOR 2008).  

The major soil orders in the Highlands are Ferralsols, Lithosols, Cambisols and Gleysols with Ferralsols occupying the largest portion (65%) (Andriamampianina et al 1997). Ferralsols are strong phosphorus fixers and strongly leached.  Dry matter yield of Elephant grass ranging from 10 to 50 tonnes ha^-1 under recommended fertilizer application was recorded in the central Highlands (FIFAMANOR et al 2008). In spite of the potential for high yields, on-farm yields of Elephant grass are much lower and variable depending on management factors such as the application of manure and/or fertilizer, cutting frequency and weed control.  Due to high costs of mineral fertilizer, manure is the main fertilizer used in mixed crop-livestock farming systems.  Manure contributes to the fertility of the soil by adding organic matter and plant nutrients but manure scarcity is a major problem.  

The present study aims to assess the effect of locally available guano organic fertilizer on growth parameters, yield and forage quality of Elephant grass.  

Material and Methods

Experimental Sites 

The study was carried out from October 2011 to March 2012 at two sites located in the Vakinankaratra region. The first site was located at the research station of FIFAMANOR (Center of Rural Development and Applied Research) (19° 48'S - 46° 08'E, 1600 masl) in the District of Antsirabe II and the second site was at Andranomody (19° 49'S - 46° 51'E, 1404 masl) in the District of Betafo.   Climatic condition of the Vakinankaratra region is humid subtropical with a mean annual precipitation of 1,300mm and a mean annual temperature of 17,1°C. There are two main seasons, a six-month warm and wet season extending from October to March and a six-month cool and dry season extending from April to September.   Soil types at the two sites were ferralsols and tropical brown soils of volcanic origin.  

Treatments and Experimental design 

The experiment was laid out in a randomized complete block design with four replicates. Treatments comprised three rates (300, 400, 500 kg ha^-1) of locally available guano organic fertilizer (4,8N-6,5P-1,2K), one rate of cattle manure (10 tonnes ha^-1) and a nonfertilized control.

Experimental plots measured 2 x 2 m. Elephant grass (cv Relaza) was established using cuttings planted in rows 0,4m apart and 0,4m apart within rows. Manure and guano treatments were broadcasted as a basal fertilizer prior to planting. Hoeing and hand weeding were carried out as deemed necessary. Treatments were harvested twice. The first harvest was done 9 weeks after planting and the second harvest 6 weeks after the first. During harvest, a stump of 5cm was left. 

Sampling and Chemical Analysis 

Green matter yield was estimated by cutting herbage from one quadrat of 1m² in the inner rows of each plot. Plant height, leaf length and tiller per plant were measured on four randomly selected plants within the quadrat at the first cut. Sub-samples (800 to 1000g wet weight) of all treatments were taken from the harvested herbage for laboratory analysis.  

Forage subsamples were cut into pieces of 5cm and oven-dried at 60°C for 72 hours for dry matter determination. Dried forage subsamples were ground to pass through a 1mm sieve for proximate analysis. Total ash content was determined by incinerating dried samples in a muffle furnace at 550°C for six hours and crude fibre content was determined by the Weende method (AOAC 1990). The nitrogen content was estimated using the Kjeldahl method and the crude protein content was calculated by multiplying the N content by 6,25.  

Statistical Analysis 

The recorded data were subjected to t-test and analysis of variance (ANOVA) followed by means separation according to the least significant difference (LSD) method (p<0,05) using the Genstat software (Buysse et al 2004).

Results and discussion

Growth parameters 

Elephant grass height at the first cut was affected by treatments but not by site nor by their interaction (Table 1). At both sites, plant height increased with guano application rate.  Plant height averaged over the two sites was 20 to 47% higher under guano treatments as compared to the unfertilized control. Bilal et al (2000) reported that height of Mott grass (Pennisetum purpureum) plant increased at all growth stages with the application of N/Farm yard manure. Saeed et al (1996) also found similar results who reported that height of Mott grass plant significantly increased with the application of N over the control.  

Mean plant height increased from 20 to 32% under 400 and 500kg ha^-1 guano rates as compared to manure treatment. This observation could be attributed to a slower decomposition and release of available plant nutrients in manure treatment compared with guano.  

Leaf length at the first cut was affected by treatment, site and their interaction. Higher leaf length was observed at the second site (Table 1). Leaf length was identical across treatments at this site. This may be related to the younger growth stage of Elephant grass at this site at this stage. The same pattern for plant height was observed for leaf length on data averaged over the two sites. Mean leaf length was 21 to 28% higher under guano treatments as compared to control and 23 to 25% higher under 400 and 500kg ha^-1 guano rates as compared to manure treatment.  

Tiller number per plant at the first harvest was not different between treatments and sites (Table 1). This result suggests stimulation of vertical rather than lateral growth of Elephant grass by guano treatments at this stage. By contrast, other studies reported that application of N-fertilizer increased number of tillers per plant of Mott grass (Saeed et al 1996; Bilal et al 2000) and Elephant grass hybrid (Aslam 1964).

Forage yields and nitrogen uptake  

Dry matter yield of Elephant grass over two cuts was affected by treatment but not by site nor by their interaction (Table 2). Guano treatments gave 43 to 57% and 39 to 54% more dry matter yield than control and manure treatment, respectively.  Mean dry matter yield was linearly related to the guano rate (y = 0,009x+7,905, R² =0,95). Crude protein yield averaged of the two sites tended (p =0.059) to be increased by guano application (Table 2), equivalent to 36 to 39% more crude protein than the unfertilized control.  Similar impact of guano application was seen in the uptake of nitrogen. Increased dry matter and crude protein yields of Elephant grass up to 80 and 300kg N/ha/year have been reported by Mohammad et al (1988) and Binh and Nung (1995), respectively. 

Apart from providing progressive release of available plant nutrients, organic fertilizer application increases soil organic matter which leads to improved soil physico-chemical properties (water holding capacity, aeration, structure, nutrient retention) and soil microbial activity enhancement (Choudhary et al 1994;  FAO 1999). 

Forage quality parameters  

Mean CP, ash and CF contents were almost identical across treatments. Pholsen et al (2005) reported that crude protein content of Signal grass treated with cattle manure at the rate of 3,12 and 6,25 t ha^-1 was similar to the control but higher at the rate of 12,5 and 25 t ha^-1. Colla et al (2004) reported a linear relationship between leaf N concentration at blooming stage of potato and guano-based organic fertilizer rates. Mohammad et al (1988) reported that Nitrogen fertilizer increased crude protein and ash percentage of Elephant grass.

Conclusion

• The application of locally available guano organic fertilizer at the rate of 300 to 500 kg ha^-1 has the potential to stimulate growth and to increase biomass yield and nitrogen uptake of Elephant grass during the year of establishment. Guano organic fertilizer is recommended as alternative to cattle manure scarcity to improve forage production in mixed crop-dairy cattle farming systems in the Highlands of Madagascar. 

References

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Received 31 August 2013; Accepted 27 November 2013; Published 1 January 2014

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