Forage yield and nitrogen nutrition dynamics of warm-season native forage genotypes under two shading levels and in full sunlight

Raquel Santiago Barro,Renato Borges De Medeiros,Carlos Nabinger,Alexandre Costa Varella,Felipe Villamil Bangel,João Carlos De Saibro,Gilles Lemaire,Igor Justin Carassai

doi:10.1590/s1516-35982012000700006

Raquel Santiago Barro, Renato Borges De Medeiros + Show 6 more

Open Access

https://doi.org/10.1590/s1516-35982012000700006

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Abstract

The successful achievement of a highly productive understorey pasture in silvopastoral systems depends on the use of well-adapted forage genotypes, showing good agronomic performance and persistence under shading and grazing. In this study, the herbage dry matter yield (DMY) and nitrogen nutrition dynamics were determined in three native warm-season grasses (Paspalum regnellii, Paspalum dilatatum and Paspalum notatum) and a forage legume (Arachis pintoi) under two shading levels compared with full sun. The experiment was conducted in the Campanha region, Bagé, state of Rio Grande do Sul, Brazil, during two evaluation cycles (2008/2009 and 2009/2010). Three shade cloth levels (0%, 50% and 80% of light restriction) were applied to the forage genotypes in a split plot design, in which shading levels were the main plot and forage genotypes were the subplots, with three replications. P. regnellii showed the highest accumulated DMY (1500 and 1700 g m-2, respectively, for the first and second evaluation cycles) at all shading levels and showed no DMY decreased under the heavy shade (80%). Average DMY over the four genotypes under the 50% shade level was higher or equal compared with full sun. Influence of rainfall was observed on the DMY performance of all genotypes: the positive effect of moderate shading (50%) on P. dilatatum and P. notatum DMY was associated to a low soil water availability status. Increased shading level resulted in high nitrogen nutrition index values on grasses, in comparison with full sun. All genotypes performed well under the moderate shading level, but the DMY of both P. regnellii and P. dilatatum and the herbage N content in P. notatum and A. pintoi of all genotypes stood out, showing that those main genotypes are promising to grow in silvopastoral systems at the Campanha region in southern Brazil.

Highlights

In sustainable silvopastoral systems, the success of the integration of herbaceous and woody components depends on the use of forage genotypes well adapted to this condition, showing good yield performance and persistence under shade
Low water supply was predominant, while estimates of evapotranspiration rates (ET) were higher than precipitation, with the greatest deficits observed in November, March and April 2009 (Figure 1)
The plant growth under moderate shading (50%) had a positive effect on the dry matter yield of grasses

Summary

Introduction

The success of the integration of herbaceous and woody components depends on the use of forage genotypes well adapted to this condition, showing good yield performance and persistence under shade. Due to the economic and environmental importance, some native forage grass genotypes from the Pampa and the Atlantic Forest biomes, such as Paspalum dilatatum and Paspalum notatum, have been more intensively studied at full sun under extensive grazing conditions (Valls et al, 2009) than under shading conditions. It is important to study the multiple physiological relationships of forages under different light levels and to select shade-tolerant genotypes to encourage farmers to apply sustainable land use systems in Southern Brazil (Saibro, 2001). Under the subtropical conditions of Southern Brazil, P. notatum and P. dilatatum species have high frequency in the native grasslands and are well recognized as well productive with highly nutritive forages (Valls et al, 2009), whereas Paspalum regnellii and Arachis pintoi are more important native forages in the Brazilian tropical regions (Ramos et al, 2010)

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