Weed seed predation in a phenologically late crop
Westerman, P.R. ; Luijendijk, C.D. ; Wevers, J.D.A. ; Werf, W. van der - \ 2011
Weed Research 51 (2011)2. - ISSN 0043-1737 - p. 157 - 164.
setaria-faberi - abutilon-theophrasti - dynamics - fields - tillage - food
Seed predation of weed seeds in crops depends on the seasonal overlap between seed availability and the activity period of the predators. Published data show that the activity period of seed predators is directly related to canopy cover. In phenologically early crops, such as cereals, maturation of leaves results in a decreasing cover prior to weed seed shed, resulting in lower seed losses than maximally possible. We hypothesised that there would be better temporal overlap in sugar beet, a phenologically late crop. The pattern of predation of Chenopodium album L. seeds was consistent over fields and years, low in July and August and gradually increasing until harvest in September/November. The patterns of seed production and shed, measured using seed traps, differed among weed species. The proportion of annual seed losses by predators calculated from these measurements ranged from 0.26 to 0.83, depending on the duration of seed exposure on the soil surface. As expected, sugar beet had better temporal overlap between predator activity and weed seed production, which may cause higher seed losses than previously reported for any other annual crop
An evaluation of four crop:weed competition models using a common data set
Deen, W. ; Cousens, R. ; Warringa, J. ; Bastiaans, L. ; Carberry, P. ; Rebel, K. ; Riha, S. ; Murphy, C. ; Benjamin, L.R. ; Cloughley, C. ; Cussans, J. ; Forcella, F. - \ 2003
Weed Research 43 (2003). - ISSN 0043-1737 - p. 116 - 129.
multispecies canopy model - abutilon-theophrasti - plant competition - winter-wheat - wild oat - simulation - growth - radiation - light - photosynthesis
To date, several crop : weed competition models have been developed. Developers of the various models were invited to compare model performance using a common data set. The data set consisted of wheat and Lolium rigidum grown in monoculture and mixtures under dryland and irrigated conditions. Results from four crop : weed competition models are presented: almanac, apsim, cropsim and intercom. For all models, deviations between observed and predicted values for monoculture wheat were only slightly lower than for wheat grown in competition with L. rigidum , even though the workshop participants had access to monoculture data while parameterizing models. Much of the error in simulating competition outcome was associated with difficulties in accurately simulating growth of individual species. Relatively simple competition algorithms were capable of accounting for the majority of the competition response. Increasing model complexity did not appear to dramatically improve model accuracy. Comparison of specific competition processes, such as radiation interception, was very difficult since the effects of these processes within each model could not be isolated. Algorithms for competition processes need to be modularised in such a way that exchange, evaluation and comparison across models is facilitated.