Hypothesis: Low oat yields are due to mineral deficies or imbalances. ("Minerals" are nutrients other than nitrogen, e.g., phosphorous, calcium, potassium, sulfur, trace elements).

"Shotgun" experiment: 17 different combinations of various minerals and manure were applied to one or two plots per treatment on each of two oat fields.

Observations: We were looking for factors that would approximetely double the yields over controls.
  • Treatments that included N had significant effects on total (crop + weed) yield but not on oats alone.
  • Treatments that included manure had positive effects on both total (crop + weed) yield and on oats alone.
  • Other treatments had little or no effect on yields.
Interpretation: Manure relieved phytotoxic effects in fields in which a lot of oat residues had been incorporated by stimulating microbial activity, & provided extra nitrogen. (We had other reasons for suspecting phytoxicity - next slide)

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