Effect of age and growing season on DM yield and leaf to stem ratio of different grass species and varieties growing in Cuba

J L Ramírez de la Ribera, C Kijora*, I L Acosta, M Cisneros López** and W Tamayo Soza

Universidad de Granma. Apdo 21, Bayamo, Granma, Cuba: MsC. Jorge L. Ramírez de la Ribera:
jlribera@udg.co.cu
*Institute of Animal Sciences, Humboldt-University Berlin, Germany, 10115 Berlin, Philippstraat 13
claudia.kijora@agrar.hu-berlin.de
**Instituto de Investigaciones Agropecuarias Jorge Dimitrov, Apdo 21, Bayamo, Granma, Cuba

Abstract

The investigation was carried out in the southeastern region of Cuba in the province Granma in 2004 and 2005. The aim was to determine the yield and leaf to stem ratio of five grasses: Panicum maximum cultivars Tanzania and Likoni, Brachiaria hibrido cultivar Mulato, Brachiaria decumbens cultivar Basilisk and Pennisetum cuba CT 169. The yield was estimated depending from growing season and regrowth length. No fertilization or irrigation was practiced.

 

The low rainfall in 2004, 50% of the average value in the last 20 years, resulted in very low yields. The grasses Pennisetum cuba CT 169, Brachiaria hibrido cv Mulato and Panicum maximum cv. Tanzania did perform well under extensive conditions in Cuba. The harvesting time should not exceed 75 days for Pennisetum and 60 days for Panicum maximum due to the stagnancy in growth. For Brachiaria the yield is permanently increasing up to 105 days growing period during rainy season.

Keywords: Brachiaria, harvest interval, nutritive value, pennisetum, regrowth, tropical grasses

Introduction

More than half of the world’s agricultural area is natural pasture land (Reynolds et al 2005). Grassland Livestock systems feed more than 800 million people from which about 200 million are living in arid and semiarid zones, where their only source of livelihood is grazing livestock (White et al 2000).

 

However, the quality and yield of pastures mainly depend on numerous factors representing ecological conditions and management practices. Between them the distribution of rainfall and fertilizing influences mainly the yield while maturity affects the feed quality.

Apart from this it is well known that cultivated pastures represent higher quality and yield than native grasslands. The increase in productivity depends on the adaptation and performance of introduced species under the respective ecological conditions.

With the breakdown of the socialist epoch in Europe, Cuba, which was strongly linked to these countries, became suddenly a country without access to high quality feed resources. As a result the livestock number decreased dramatically and the agriculture had to focus at local feed resources to satisfy the demand of the people.

Cuba has large grassland area of 2.2 million hectares; representing 23% of the agricultural area.  In the last few years efforts were made to develop new grass varieties and to evaluate species successful established under similar ecological conditions.

The objective of this investigation was to compare the yield and leaf to stem ratio of 5 varieties of 3 grass species growing in two seasons and for different regrowth lengths in the province Granma, Cuba.

Materials and methods

Study area

 

The investigation was carried out in “Hermanos Lottis” enterprise in Granma province in the southeastern region of Cuba. The average monthly temperature, humidity and rainfall during dry season and rainy season amounted in 2004: 21.1°C and 32.3°C; 75% in average; 11mm and 95 mm and in 2005: 24,3°C and 27,3°C; 71% and 81%; 32 mm and 190 mm respectively.

 

The soil is Alluvial Little Differentiated.  The soil is Alluvial with a pH of 6.2, P, K and N content of 1.1, 32 and 34 mg/100g soil respectively. The organic matter content amounted 3.2%.

 

Characterization of grass species

 

The 3 grass species and varieties were Panicum maximum cultivars Tanzania and Likoni, Brachiaria decumbens cv. Basilisk, Brachiaria hibrid cv. Mulato and Pennisetum cuba CT 169.

 

Panicum maximum cv. Tanzania is a species introduced in Cuba from United States of America in 2001 and widely spread all over the country. Panicum maximum cv. Likoni introduced in Cuba from Mexico in 1975. Brachiaria hibrid cv Mulato introduced in Cuba from United States of America in 2001. Brachiaria decumbens cv Basilisk introduced in Cuba from Uganda in 1972, this species is common in the whole country. Pennisetum cuba CT 169 (Pennisetum purpureum) was prepared by the techniques of tissue culture in Cuba in the Institute of Animal Sciences; the number of clones gave 169 their name.

 

Pasture management

 

In May 2002 five plots of 1600m² each (10*160 m) were sow to the five grasses at non-irrigated and non-fertilized field having the first cut in June 2003. In January 2004 and 2005 the whole area was cut at 10 cm height. No fertilizer or irrigation was applied. After 30, 45, 60, 75, 90 and 105 days of regrowth length the yield was determined. The total area was cut again in July and the same regrowth periods were used to estimate the yield for the rainy season. Yield estimation was done by visual method according to Haydock and Shaw (1975) as described shortly followed. In the first step 5 areas with highest, medium (3 areas) and lowest height and density were identified visual. After that 60-100 replicates of 0,25m² area were harvested, weighted and assigned to one of the five reference areas, to determinate the frequency of yield groups. Under consideration of the distribution in the yield groups the total yield was calculated for the whole area.

 

For the determination of the leaf to stem ratio (only samples of 2005), an area of 0.25 m², was harvested, dried, weighed, leaf and stem were separated and weighed again, with five replicates for each sample. The potential yield per year was calculated under consideration that rainy season and dry season is distributed equal during the year.

 

Statistical analyses

 

Data were subjected to analysis of variance (ANOVA) using the Newman Keuls multiple range test in a randomized block design available  in a factorial arrangement (3x3) with 4 replications in statistic version 6.0 for windows 2003.

 

For the normal distribution of the data the test was used of Kolmogorov-Smirnov. For the homogeneity of the variances the test was used of Bartlett.

 

The following model was used for statistical analysis:

Y_ijk = µ + a_i + s_j + sp_k + (as)_ij+(asp) _ik + (ssp)_jk+(assp)_ijk+ e_ijk

Where

Yijk is the response variable (DM yield, leaf to stem ratio),
µ the over all mean,
a_i the age,
s_j the season,
sp_k the species and
₊ e_ijk the random error

 

Results  

Due to the extremely low rainfall in 2004, 50% of the average values of the last 25 years the analysis of the yield were considered separately for 2004 and 2005.

 

Table 1 shows the results of the analysis of variance of the yield 2004 and 2005 and the leaf to stem ratio in 2005. High differences in yield must be considered as the 3.3 fold mean value in 2005 compared to 2004 indicates.

All tested factors, which are, species, season and age as well as all interactions significantly influenced the DM yield and the leaf to stem ratio. The model explains 92-98% of the variation and the coefficient of variation is very low between 0.13 and 0.64. This indicates that the main influencing factors were considered in the model. The over all mean of the DM yield was 1.54 t DM/ha in 2004 and 5.15 t DM/ha in 2005 and the leaf to stem ratio amounted 1:0.67.

 

Mean values and standard errors of the DM yield and leaf to stem ratio in 2005 are illustrated in table 2. The highest yield was obtained in the species Pennisetum cuba.

Compared to the Brachiaria and Panicum maximum species the yield exceeds the values by 1.4 to 2.2 times. Both between the Brachiaria varieties and the Panicum maximum varieties those cultivars showed higher DM yield, which were introduced recently from the USA. The differences in yield are remarkable about 50-60%.

 

The differences in leaf to stem ratio were not high between the species. A comparison within the species showed higher stem proportion for the varieties with higher DM yields. The growing season dramatically influences the yield values with a 3.3 fold increase in the rainy season. The proportion of leaf is much higher (by 47%) at grasses grown during the dry season than in the rainy season.

 

As expected the yield increased continuously with longer growing period. During growing up the leaf to stem ratio changed from 3.3:1 to 0.84:1. The total DM yield per ha per year in 2004 is indicated in table 3. Highest potential yield was estimated for Pennisetum cuba with 12.3 t DM/ha. Between the two cultivars of Brachiaria and Panicum maximum the last introduced from USA exceeded the yearly possible yield significant compared to the older cultivars. The differences are between 15 and 25%.

Table 4 illustrates the results of the year 2005. Compared to 2004 the yield performance of Pennisetum cuba exceeds the value by 270%. The differences between the cultivars of Brachiaria and Panicum maximum were much higher than in 2004 and exceeded the yearly possible yield by 50-80% compared to the older cultivars.

 

Figures 1-3 illustrate the course of yield for the grass varieties of 3 species during the two main seasons depending from the regrowth length in 2005.

All figures indicated definitely the differences between rainy and dry season. For Brachiaria and Panicum maximum species the curve is continuously increasing up to 105 days (except Brachiaria decumbens cv Basilisk 105 day value) during the rainy season. For Pennisetum cuba the yield arrived a plateau after 75 days of regrowth length. During the dry season the growth potential of all species is strongly limited, with highest potential for Pennisetum.

 

Discussion 

The high rainfall differences between 2004 and 2005 are an indication of uncertainty of feed availability in tropical countries caused by climatic effects. The result of the unusual very dry year 2004 explains the necessity of investigation for new grass species.

 

Under normal Cuban climatic conditions, which are characterized by a strong rainy season (about 1000 mm rainfall) and long periods of drought during the year, the investigation indicated, that all tested species are well adapted.

 

On the other hand the effects and the interaction of these effects, showed highly significant differences, given fundamentally by the inequality of the biological cycles and growth of these species; as well as their behavior in the seasons of the year about the yield and proportion leaf stalks. The Pennisetum is superior to all the species in the two seasons, keeping in mind that it was a species obtained for via biotechnical with the objective of its best adaptation to the climatic conditions of Cuba.

 

Brachiaria species are native in Africa (Uganda) but now widely distributed in tropical climate worldwide. In South America it is the most cultivated grass species, especially the cultivar Basilisk. Its classification for decumbens or bizanthia is controversial (CIAT 2000), but predominant considered as decumbens.

 

The cultivar Mulato is described to have a 25% higher yield than other commercial brachiaria species, as Peters et al (2003) in South America estimated.

 

The superiority of Mulato was confirmed also in this investigation. The yield increase amounted more than 50% compared to the cultivar Basilisk. For the cultivar Basilisk a decrease in the yield after 90 days growing period was obtained, like (Espinosa 2006) also described.

 

The high yield was achieved although no fertilizer and irrigation was used. This indicates the excellent adaptation of this cultivar to the marginal conditions in Cuba.

 

The possible yields for Brachiaria are described to range between 10 and 30 t DM/ha per year (Pinzón y Santamaría 2005). In studies carried out by (Febles et al 1994) with Brachiaria decumbens DM yields of 23 and 19.3 t/ha/year were obtained with dose of 100 kg and 200 kg N/ha/year respectively. The renunciation of fertilizer decreased the yield to 8.5 t DM/ha/year. For the species Brachiaria hibrido cv Mulato (Guiot and Melendez 2003) determined a DM yield of 25 t /ha / year.

 

With 22 t DM per ha and year estimated in this investigation without any fertilization the yield is considered to be high for the cultivar Mulato. In contrast the cultivar Basilisk is less productive and not suitable for the low management practices in Cuba.

 

Panicum maximum also originates in Africa and is worldwide distributed in all tropical countries. The cultivar Likoni is recommended in high rainfall areas (Padilla et al 2001).  Nevertheless the yield is lower than for cultivar Tanzania even in the rainy season. The superiority of the cultivar Tanzania was estimated also by (Cruz et al 2005) tested under comparable agroecological conditions. (William and Black 1994) indicated the high level of plasticity, which makes the cultivation of this grass in different climatic regions possible. The increase rate of DM yield is particularly high during the first 60 days of growth. The DM yield of 6.6 and 9.4 t/ ha during 45 and 60 days growing period is under the given conditions very high and comparable with the 7t DM/ha harvested after 35 days during the rainy season measured by (Garcia et al 2004), achieved by fertilizing with 300kgN/ha.

 

The species Pennisetum cuba CT 169 a variety of Pennisetum purpureum is thoroughly growing in Cuba and started to extend to Mexico and Brazil. Although its cultivation is increasing, investigation for this species is scarce. Pennisetum cuba CT 169 is comparable with the Cuban cultivar Pennisetum cuba CT 115 but it is described to have a higher yield potential and wider leafs to stem ratio (Herrera 2005).

 

The superiority of Pennisetum purpureum compared to the other grasses is documented in the literature (Martínez et al 1996). In Cuba maximum yield is described to be 120 t original matter/ha/year (about 50 tons dry matter) in the first cut (Santana et al 1998).

Harvesting at 75 days produced the same DM amount as longer growth lengths. So harvesting at higher maturity stages is not recommended.

 

During the rainy season the differences in yield between all grasses are considerable but not high during the dry season.

 

The leaf to stem ratio is an indicator for the quality of grasses, because the leaves contains more valuable nutrients. Remarkable differences exist between dry and rainy season, but the low yield during dry season cannot compensate the produced nutrient amount. (Beliuchenko and Febles 1980) explained the higher stem content in plants during the rainy season with increased requirement for strength due to faster growth.

 

While the new cultivars indicated their superiority under ordinary whether conditions in this region the old ones had lower yield losses under extreme dry conditions like in year 2004.

 

Conclusions

• The grasses Pennisetum cuba CT 169, Brachiaria Hibrido cv Mulato and Panicum maximum cv. Tanzania did perform well under extensive conditions in Cuba. The harvesting time should not exceed 75 days for Pennisetum and 60 days for Panicum maximum due to the stagnancy in growth. For Brachiaria the yield is permanently increasing up to r 105 days growing period during rainy season.

  
  

• The leaf to stem ratio decreased with higher maturity and in the rainy season compared to dry season.

 

References 

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Received 16 April 2008; Accepted 2 July 2008; Published 4 September 2008

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