| dc.contributor.author | Yang, Chengzhi. | en_US |
| dc.date.accessioned | 2014-10-21T12:36:41Z | |
| dc.date.available | 1997 | |
| dc.date.issued | 1997 | en_US |
| dc.identifier.other | AAINQ24787 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55529 | |
| dc.description | Yield instability in fababean is a limitation to more widespread use of this potentially high yielding, N$\sb2$-fixing crop. I hypothesized that high levels of residual N and P from other crops could reduce yields by stimulating pests, diseases, and weeds, and by suppressing rhizobial and mycorrhizal symbionts; also that deficiencies of K would increase susceptibility to pests and diseases. There were three components to the research: (1) A correlational study involving observations of soil and plant variables (yields, roots, symbionts, leaf nutrients) on manually weeded plots and unweeded plots was conducted on farmer-grown crops on 8 farms in Prince Edward Island (PEI). These farmers had eliminated or were reducing use of synthetic fertilizers and chemical controls of weeds, pests and diseases. (2) Prior to seeding fababean, N, P, K and Ca fertilizers were added to replicated plots on two farms in PEI (except for Ca) and two in Nova Scotia (NS) and to large concrete cylinders containing soils of low (LF) and high (HF) background fertility. All plots were weeded manually except at NS1 where non-weeded treatments were also included. Rock-P was included as an additional treatment in the cylinders. (3) Rhizobial and mycorrhizal isolates from each of two farms were inoculated individually and in different combinations onto plants grown on artificial medium in a growth chamber. Plant variables were observed in (2) and (3). | en_US |
| dc.description | Grain yields varied widely in the 8-farm study, and were highly correlated with leaf K, but not with nodulation, mycorrhizal levels or weeds. Positive responses to K were observed in the fertilizer experiments. Adding N suppressed nodulation, but not yields. All fertilizers suppressed mycorrhizae at all sites except for N, P and K in the LF cylinders. Super-P increased nodulation and yield in the LF cylinders, but rock-P did not. At farm NS1, adding N increased losses of yield due to weeds. N increased levels of an insect pest in the HF but not in the LF cylinders. In the growth chamber experiments, inoculants that included mycorrhizae effected increases in grain + pod yield at levels of infection below those observed in the field. It is concluded that variation in soil K is a major factor in yield variation of fababean in PEI and NS. The critical and maximum normal leaf K levels appear to be higher than in other grain legumes. It is suggested that the high requirement for K is related to high yield and drought susceptibility of fababean. Nutrient suppression of mycorrhizal infection appears not to have negative effects on the crop, however complete elimination of mycorrhizae could have negative effects. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1997. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Agriculture, Agronomy. | en_US |
| dc.subject | Environmental Sciences. | en_US |
| dc.title | Soil fertility effects on yield, pests, weeds and symbionts of fababean (Vicia faba L.) in ecological farming systems. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
