Q2. What is the main reason for the low aflatoxin concentration in peanuts?
Shorter periods of drought (<20 days), and drought early or late in the season, also result in lower concentrations of aflatoxin (and see Azaizeh et al., 1989).
Q3. What is the way to predict infection and contamination in peanuts?
Infection and contamination can be predicted in peanuts using the fraction of extractable soil water when soil temperatures are not limiting aflatoxin contamination.
Q4. What is the main reason peanuts are important in Niger?
Peanut is an important crop in Niger, even though growing seasons are short and variable, and drought and high soil temperatures are common (Ntare and Williams, 1998).
Q5. What was the effect of the sowing date on plant establishment?
Plant stands were generally<10 m2 and in some cases as low as 2.4 plants m 2. Clearly drought, and probably nematodes (Sharma et al., 1992; Waliyar et al., 1992) had a substantial effect on stand establishment.
Q6. What are the main types of aflatoxins in peanuts?
Aflatoxins are toxic, carcinogenic, teratogenic and immunosuppressive substances (Turner et al., 2000; Wild and Hall, 2000; Hall and Wild, 2003) produced when toxigenic strains of the fungi Aspergillus flavus Link. ex Fries and A. parasiticus Speare grow on peanuts and many other agricultural commodities.
Q7. What is the way to determine the stress of a crop?
Many crop simulation models use FESW (or fraction of transpirable soil water, fraction of available soil water) as there is a consistency in plant responses across a wide of conditions (Sinclair et al., 1987) and as such FESW is a useful physiological (stress) index.
Q8. How many ml of diluted extracts were placed into the wells?
To determine aflatoxin concentration from each dilution (1:15, 1:75 and 1:375), 50 ml of diluted extracts were placed in duplicates into the wells.
Q9. What was the effect of aflatoxin on pod yields in 1992?
Pod yields across all treatments in this study were variable (mean 306 kg ha 1, RMSD 244 kg ha 1) and in a number of years pod yields were higher in rainfed than irrigated plots, with pod yield at S1 in 1992 anomalously high.
Q10. How did the weather affect the pods?
Mean daily air and soil temperature during pod-filling averaged 28–30 and 31–35 8C, respectively, generally increasing towards the end of the season as rainfall declined (Fig. 1).
Q11. What is the main conclusion of this study?
In conclusion, this study has shown that infection and contamination occurred in the field in Niger even when stress periods were short.
Q12. What was the average FESW in the last 25 days of podfilling?
In the experiments reported here infection was widespread and aflatoxin was found at concentrations >30 mg kg 1 at all treatments in 1992–1994 when average FESW in the last 25 days of podfilling was between 0.09 and 0.67 and average soil temperatures (at the nearly meteorological station) were between 31 and 35 8C.
Q13. How was the Pod yield data compared to the observed values?
Pod yield data was fairly variable, and original replicate data was re-checked to confirm values, resulting in missing values being substituted for observed values in four plots.
Q14. How did the model predict phenology and yield of the whole data set?
The model predicted phenology and yields of the whole data set reasonably well (Fig. 2; r2 = 0.67, P < 0.001, n = 40), with a root mean square deviation (RMSD) of 244 kg ha 1.