NEW Parasite publication online in Field Crops Research

We are glad to share with you yet another PARASITE project publication recently published in Field Crops Research. The manuscript is entitled: "Fertilisers differentially affect facultative and obligate parasitic weeds of rice and only occasionally improve yields in infested fields” and is co-authored by Dennis E. Tippe, Lammert Bastiaans, Aad van Ast, IbnouDieng, Mamadou Cissoko, Juma Kayekee, Derek W. Makokha and Jonne Rodenburg.

In this manuscript, we reported on an experimental field study undertaken in two rice production environments in southern Tanzania. Our aim was to test whether different fertilisers: (1) suppress the obligate parasitic weed Striga asiatica (upland) and the facultative parasitic weed Rhamphicarpa fistulosa (lowland), and (2) favour rainfed rice yields under parasitic weed infestation. The research covers four years of field experiments in southwest Tanzania, in a S. asiatica infested rainfed upland and a R. fistulosa-infested rainfed lowland field. Treatments included sole mineral (NPK or Di-Ammonium Phosphate —DAP—plusurea), organic (cattle manure or rice husk), combinations of mineral and organic fertilisers and a no-fertiliser control.

Our study shows that, fertilisers moderately suppressed the obligate parasite S. asiatica, but no correlations between infestation level and soil fertility status were observed. In the lowland field, fertilisers, in particular the ones that included organic components, promoted the facultative R. fistulosa Plant available phosphorus, exchangeable potassium and soil organic matter content correlated with R. fistulosa infestation levels. Positive fertiliser effects on yields were found in both parasitic weed infested fields, except in years with high S. asiatica infestation levels. Rice husks alone and rice husks or manure combined with DAP and urea increased yields and soil fertility most. We conclude that fertilisation differentially affects the obligate and facultative parasitic weeds of rice systems; obligate parasites may be slightly suppressed, but facultative parasites may even be stimulated. Meanwhile, consistent rice yield increases under parasitic weed infested conditions cannot be obtained with fertiliser application when parasitic weed infestation levels are too high.

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