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Critical Petiole Nitrate-Nitrogen for Lint Yield and Enhanced Maturity in Pima Cotton

Tewolde, Haile, Fernandez, Carlos J., Foss, D. C., Unruh, Larry G.
Agronomy journal 1995 v.87 no.2 pp. 223-227
plant nutrition, Gossypium barbadense, petioles, nitrate nitrogen, early development, crop yield, lint cotton, soil fertility, nitrogen, nutrient deficiencies, Texas
Petiole NO-N concentration (PNN) has been recommendaeds indicator of midseason N deficiency in upland cotton (L.). Its use in Pima cotton (L.) managemeenstp, ecially when early maturity is the goal, is not well documented. A 3-yr study evaluated PNN as an indicator of N status in Pima cotton in order to identify a critical minimum PNN level for yield and early maturity. Treatments were five preplant applied N rates of 0 to 180 kg ha in 1990 and 0 to 269 kg ha in 1991 and 1992. The PNN was measured throughout boll development, starting ≈ 2 wk before or at first flower. Applied N significantly(≤ 0.05) affected PNN in 1991 and 1992, when residual soil N was low, but not in 1990, when residual N was high; differences among treatments in 1991 and 1992 were largest during early flowering. PNN was a good indicator of plant.N status within but not across seasons. Based on early-flowering samples, the critical PNN level for lint yield was 3.84 g kg in 1991 and only 1.75 g kg in 1992; in 1990, residual soil N alone resulted in PNN much higher than the critical levels in the othery ears. PNN < 2 g kg in 1991 and < 1 g kg in 1992 resulted in earlier maturity, but also resulted in less lint yield. Pima cotton PNN did not exceed an average of 11 g kg, in contrast to 24 to 30 g kg reported for upland cotton. Plant growth or petiole anatomical variables that cause year-to-year variation in PNN should be identified and the necessary normalization made before PNN can be used as a midseason diagnostic tool in Pima cotton.