Environmental quality improvement of agricultural lands through silvopasture in southeastern United States

Abstract

We hypothesized that, because of the ability of trees to sequester carbon (C) in the deep soil profile and remove excess nutrients from soils, the silvopastoral agroforestry system could enhance the environmental quality of the agricultural lands. To test this hypothesis, two sets of experiments were conducted in two soil orders in Florida, Spodosols and Ultisols, with two major objectives: i) determining the soil C accumulation and tracing the plant sources of C in soil fractions, and ii) quantifying water soluble phosphorus (WSP) and estimating the Soil P Storage Capacity (SPSC). Total C in both soil orders was greater under silvopasture than in treeless pastures, particularly at lower depths. Stable-isotope signature analysis suggested that C 3 plants (in this case, slash pine, Pinus elliotii) contributed to a more stable C fraction than C 4 plants (in this case, bahiagrass, Paspalum notatum) at soil depths up to 1 m. WSP was consistently higher in treeless pastures, while the remaining SPSC was lower in this land-use system, suggesting the greater likelihood of P moving out of the soil under treeless pasture than in silvopasture. Thus, the presence of trees in pastures contributed to more stable C within the soil profiles, lower WSP, and greater SPSC, indicating more environmental benefits provided by silvopastoral systems as compared to treeless pastures under similar ecological settings. Key words: carbon sequestration, nutrients, soil P storage capacity, treeless pasture MELHORIA DA QUALIDADE AMBIENTAL DE TERRAS AGRICULTÁVEIS POR MEIO DA SILVOPASTAGEM NO SUDESTE DOS ESTADOS UNIDOSRESUMO: Nossa hipótese é de que devido à habilidade das árvores seqüestrarem carbono (C) no perfil profundo do solo e remover o excesso de nutrientes dos solos, o sistema de silvopastagem agroflorestal poderia melhorar a qualidade ambiental de terras agricultáveis. Para testar esta hipótese, dois grupos de experimentos foram conduzidos em duas ordens de solos na Florida, Espodossolos e Ultissolos, com dois objetivos principais: i) determinar a acumulação de C do solo e investigar as fontes de C para as plantas nas frações dos solos, e ii) quantificar o fósforo solúvel em água (FSA) e estimar a capacidade de armazenamento de fósforo no solo (CAFS). O C total em ambos os solos foi maior sob o sistema de silvopastagem do que sob pastagens com menos árvores, particularmente nas profundidades mais baixas. A análise por assinatura de isótopo estável sugeriu que as plantas C 3 (neste caso, slash pine, Pinis elliotti) contribuíram mais para a fração estável do carbono do que plantas C 4 (neste caso, bahiagrass, Paspalum notatum) nas profundidades dos solos acima de 1 m. O FSA foi consistentemente maior em pastagens com poucas árvores, enquanto que a CAFS foi mais baixa neste sistema, sugerindo a grande probabilidade do fósforo ser mais facilmente movido do solo sob pastagens com poucas árvores do que nos sob silvopastagem. Deste modo, a presença de árvores em pastagens contribuiu para C mais estável nos perfis dos solos e o mai...

Changes in Soluble-N in Forest and Pasture Soils after Repeated Applications of Tannins and Related Phenolic Compounds

“…The effects of tannins on soil organic matter and nutrient cycling have important implications for livestock production in mixed systems such as silvopastures that include a mixture of forages together with browse and overstory tree species [61][62][63][64]. Appalachian silvopasture soil typically differs from International Journal of Agronomy the surrounding unmanaged woodland because it is limed to increase soil pH, receives additional N-inputs from fertilizers and manure, and can develop greater bulk density due to compaction by livestock (Table 1).…”

Native trees and shrubs for the productive rehabilitation of tropical cattle ranching lands

“…Throughout continental Europe and the British Isles the conservation or restoration of such systems is being promoted for biodiversity enhancement (McAdam and McEvoy, 2009). In humid regions, SPS can sequester more carbon than pastures and store it deeper and more permanently Nair et al, 2007a;Haile et al, 2010). The combination of grasses and trees also helps retain soil and water, protecting watersheds and soils from erosion (Ibrahim et al, 2006) and nutrient pollution (Michel and Nair, 2005;Michel et al, 2007).…”

Carbon Storage of Different Soil‐Size Fractions in Florida Silvopastoral Systems

“…Silvopasture—integrating trees into pasture and forage plant production—is the most widespread form of agroforestry in North America (Garrett et al, 2000; Nair et al, 2005). Available information suggests that silvopastoral systems are an ecologically sustainable and environmentally desirable approach to reduce excessive nutrient loss from open pastures and thereby reduce eutrophication of adjacent water bodies (Nair et al, 2007a). In areas where nutrient pollution is a very serious environmental problem (e.g., in the coarse‐textured soils of the southeastern USA), silvopasture could be an alternative land‐use option particularly for non‐industrial private forest land owners and livestock operators.…”