Productivity and botanical composition of Mediterranean grassland in relation to residual phosphate

Abstract

The effects of residual phosphate (P) fertilizer were monitored for six seasons on Mediterranean grassland. The phosphate fertilizer was originally applied annually at three rates (0, 25 and 60 kg P2O5/ha) for 7 years (1984–1990) to phosphate-deficient grassland at Tel Hadya, northern Syria. The herbage biomass productivity, botanical composition and the seed bank in the soil were monitored for six seasons (1991/92–1996/97). The experiment was grazed at two annual stocking rates (1·1 sheep/ha (low) and 2·3 sheep/ha (high)). The experimental site was typical of native grassland within the cereal zone of west Asia, where cropping is not possible because of shallow, stony soils and steep slopes.Available soil phosphorus in May 1991 was 6·5, 20·8 and 40·1 mg P/kg under the 0, 25 and 60 kg P2O5/ha treatments and 6·6, 13·4 and 14·8 mg P/kg respectively, in May 1997. Yields of both legumes and total herbage (legume+grass+other species) were significantly influenced by the residual phosphate. Legume yields were between 6- and 7-times the control yield in the first two years of the study. This decreased with time but was still in the range of 1·5 to 1·9 times the yield of the control in 1997, six years later. Total herbage yield was consistently higher on the plots previously fertilized with P, which ranged between 1·5- and 2·5-times the control. Both legume seed and grass seeds were significantly larger with residual P, which ranged between 5·4- and 2·0-times the control for the legume and 2·5- and 1·4-times for the grasses. All these factors have practical implications for the use of P fertilizer on grassland which could help control soil erosion and improve livestock production on marginal lands on which farming communities largely depend.

Carbon sequestration in dryland ecosystems of West Asia and North Africa

“…Most soils have low SOC content ranging between 0Á2 and 0Á8 per cent. Low levels of SOC content have also been reported from soils of Pakistan (Rashid et al, 1988), Iraq (Aziz et al, 1988), and elsewhere in the WANA region (Amar and Houssa, 1988;Bowman et al, 1999;ICARDA, 1991;Khalil and El-Shinawi, 1989;Osman et al, 1999;Ryan and Matar, 1988). However, not all soils have low SOC content, which in some soils may be 1Á5±2Á0 per cent (Yurtsever and Gedikoglu, 1988).…”

Relationship between Plant Species Diversity and Plant Biomass of Orchard Grass and Lucerne Sown in Different Ratios in the Province of Salamanca, Spain

“…Seligman (1996) argues that most Mediterranean grasslands grow in soils deficient of one or more nutrients, for example, pasture production is poor in areas of low soil phosphorus availability. Although, an increase of legume species in the plant cover may be obtained by the addition of phosphorus (Osman et al, 1991(Osman et al, , 1999Henkin et al, 1998). When there is a nitrogen enrichment (Foster & Gross, 1998), the high productivity tends to reduce species diversity (Tilman & Pacala, 1993;Janssens et al, 1998).…”

Factors affecting the establishment and growth of annual legumes in semi-arid mediterranean grasslands

“…Fertilization is an effective management practice aiming at quantitative and qualitative improvement of herbage (Menke 1989;Osman et al 1999). Phosphorous (P) especially is essential for the legume establishment though it is known that plant response to P fertilization is expected only in wet years (Henkin and Seligman 2000).…”

“…Phosphorous (P) especially is essential for the legume establishment though it is known that plant response to P fertilization is expected only in wet years (Henkin and Seligman 2000). Generally, P fertilization alters species composition in grasslands by favouring legumes at the expense of grasses (Papanastasis and Koukoulakis 1988;Osman et al 1999;Henkin et al 2006).…”