Growth responses of sugarcane to mycorrhizal spore density and phosphorus rate

Abstract

Abstract. Arbuscular mycorrhizal (AM) fungi, commonly found in long-term cane-growing fields in northern Queensland, are linked with both negative and positive growth responses by sugarcane (Saccharum spp.), depending on P supply. A glasshouse trial was established to examine whether AM density might also have an important influence on these growth responses. Mycorrhizal spores (Glomus clarum), isolated from a long-term cane block in northern Queensland, were introduced into a pasteurised low-P cane soil at 5 densities (0, 0.06, 0.25, 1, 4 spores/g soil) and with 4 P treatments (0, 8.2, 25, and 47 mg/kg). At 83 days after planting, sugarcane tops responded positively to P fertilizer, although responses attributable to spore density were rarely observed. In one case, addition of 4 spores/g led to a 53% yield response over those without AM at 8 mg P/kg, or a relative benefit of 17 mg P/kg. Root colonisation was reduced for plants with nil or 74 mg P/kg. For those without AM, P concentration in the topmost visible dewlap (TVD) leaf increased significantly with fertiliser P (0.07 v. 0.15%). However, P concentration increased further with the presence of AM spores. Irrespective of AM, the critical P concentration in the TVD leaf was 0.18%. This study confirms earlier reports that sugarcane is poorly responsive to AM. Spore density, up to 4 spores/g soil, appears unable to influence this responsiveness, either positively or negatively. Attempts to gain P benefits by increasing AM density through rotation seem unlikely to lead to yield increases by sugarcane. Conversely, sugarcane grown in fields with high spore densities and high plant-available P, such as long-term cane-growing soils, is unlikely to suffer a yield reduction from mycorrhizal fungi.

Effects of compost and chicken litter on soil nutrition, and sugarcane physiochemistry, yield, and injury caused by Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae)

“…However, adding P does not always elicit a strong growth response in sugarcane (Kelly et al, 2001(Kelly et al, , 2005. The enriched soil nutrient content in the high compost treatment was also evident from the substantially greater production of first-season water (164) (8) (84) sprouts than in other treatments.…”

Soil fungal and bacterial biomass determined by epifluorescence microscopy and mycorrhizal spore density in different sugarcane managements

“…ZANGARO et al (2000) found that trees in later forest succession stages are less dependent than pioneer tree species in initial phases of succession, meaning that forest in climax are not responsive to AMF root colonization. Similarly, KELLY et al (2005) studying growth responses of sugarcane to different mycorrhizal spore density concluded that sugarcane is poorly responsive to AMF, although it is unlikely that longterm sugarcane fi elds suffer a yield reduction because of mycorrhizal root colonization.…”

Anatomy and Morphology

“…Arbuscular mycorrhizae including Glomus spp. have also been found in the roots and rhizosphere of field-grown sugarcane plants, although no clear contribution to plant nutrition has been demonstrated (Kelly et al 2005).…”