PARENT SESSION
Oral Session #60: Agroecology- Sustainable Agriculture.
Presiding: R. Bohanan
Wednesday, August 7. 8:00 AM to 11:30 AM. Mesquite Room, Radisson.
Nodule abundance on peanut in semi-arid Zimbabwe and interactions with mycorrhizal fungi.
Besmer, Ylva*,1, Koide, Roger1, Myers, Robert2, 1 Penn State University, University Park2 ICRISAT-Bulawayo, Zimbabwe
ABSTRACT- Rotations with legumes have been suggested as a means to increase cereal production in low-input agriculture in Zimbabwe, as cereal yields are currently limited by nitrogen (N). However, N2 fixation by legumes is often phosphorus (P) limited. Arbuscular mycorrhizal (AM) fungi can increase plant P uptake. The objective of this study was to determine the inoculum potential of rhizobia and AM fungi on peanut in eight soils collected from semi-arid Zimbabwe. The soils ranged widely in pH and texture. Peanuts were grown in the soils for six weeks in a greenhouse without fertilizers. Both nodulation and AM colonization varied significantly among soils at the end of the experiment. Sixty-eight percent of the variation in nodulation could be explained by soil available P (Olsen). AM colonization was not a good predictor of nodulation, probably due to the sensitivity of AM fungi to the low pH and high available P in some soils. Inoculations with AM fungi in a sandy soil with little available P and moderate nodulation and AM colonization, increased nodulation and significantly increased N content of the shoot. P applications indicated that the AM fungal effect was P mediated. This study suggest that optimizing the interaction between legumes, bacteria and AM fungi may increase N2 fixation in subsistence agriculture without the application of costly fertilizers. Methods for stimulating AM fungal activity in the field are currently being investigated and will be discussed.
KEY WORDS: Arbuscular mycorrhiza, rhizobia, phosphorus, peanut