Addressing soil variability in low nitrogen breeding programs
1997
Laffite, H.R. | Banziger, M. | Edmeades, G.O. | Bell, M.A.
When crop improvement is conducted under conditions of low soil nitrogen supply, the relative magnitude of experimental variability tends to increase, and this can mask differences among genotypes. Some recommendations for managing low-N nurseries emerged during the course of a recurrent selection program to improve the yield of tropical maize grown with limited soil N. This program was conducted on a site with alluvial soils, which are characterized by considerable spatial variation in soil texture and N- supplying capacity within each experimental area. Incomplete block designs were very effective in improving experimental efficiency for evaluations of progeny grown at low N. Covariate adjustments based on check yields in previous seasons were effective for yield testing of experimental cultivars. The mean chlorophyll concentration of adjacent rows in the same season was also highly correlated with yield, and served as an effective covariate. The soil parameters examined (nitrate level of air-dried soil prior to planting, organic matter content, and penetrometer resistance) were less effective covariates than were historical yields of check entries, provided those check yields had been collected after the field had reached a low N level. Yearly collection of variability data is not required at this location.
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