Theme 06: Abiotic Constraints to Forage Production from Grasslands
Description
Tropical forages growing in low-fertility acid soils usually increase the amount of dry matter partitioned to roots at the expense of shoot growth, but substantially different adaptive attributes to such soils have been found, both between and within species. By possessing the C4 pathway of photosynthesis, grasses are more efficient than legumes in using N, Ca, and P, whereas legume roots are more efficient in extracting nutrients from low-fertility soils. Phosphorus uptake efficiency (mg of P uptake in shoot biomass per unit root length) of the legume Arachis pintoi is several times higher than that of the grass Brachiaria dictyoneura. But the grass’s P use-efficiency (g of forage produced per g of total P uptake from soil) is markedly higher than that of the legume. The superior ability of legume roots to acquire P from different inorganic and organic P sources was associated with higher levels of inorganic P in roots. For Al resistance, the grass Brachiaria shows considerable variation. For example, B. decumbens cv. Basilisk is much more resistant to Al toxicity than are other Brachiaria species. A rapid and reliable screening procedure was developed, based on findings from physiological studies, to identify Al-resistant genotypes and improve the efficiency of CIAT’s on-going Brachiaria breeding program. The use of such screening methods will help breeders develop superior genotypes that combine several desirable traits to improve pasture productivity and combat pasture degradation.
Included in
Adapting Tropical Forages to Low-Fertility Soils
Tropical forages growing in low-fertility acid soils usually increase the amount of dry matter partitioned to roots at the expense of shoot growth, but substantially different adaptive attributes to such soils have been found, both between and within species. By possessing the C4 pathway of photosynthesis, grasses are more efficient than legumes in using N, Ca, and P, whereas legume roots are more efficient in extracting nutrients from low-fertility soils. Phosphorus uptake efficiency (mg of P uptake in shoot biomass per unit root length) of the legume Arachis pintoi is several times higher than that of the grass Brachiaria dictyoneura. But the grass’s P use-efficiency (g of forage produced per g of total P uptake from soil) is markedly higher than that of the legume. The superior ability of legume roots to acquire P from different inorganic and organic P sources was associated with higher levels of inorganic P in roots. For Al resistance, the grass Brachiaria shows considerable variation. For example, B. decumbens cv. Basilisk is much more resistant to Al toxicity than are other Brachiaria species. A rapid and reliable screening procedure was developed, based on findings from physiological studies, to identify Al-resistant genotypes and improve the efficiency of CIAT’s on-going Brachiaria breeding program. The use of such screening methods will help breeders develop superior genotypes that combine several desirable traits to improve pasture productivity and combat pasture degradation.
