Comparison of adjuvant effects on cotton leaf potassium concentration and lint yield
Titel:
Comparison of adjuvant effects on cotton leaf potassium concentration and lint yield
Auteur:
Heitholt, James J.
Verschenen in:
Journal of plant nutrition
Paginering:
Jaargang 17 (1994) nr. 12 pagina's 2221-2233
Jaar:
1994-11
Inhoud:
Visual mid-season potassium (K) deficiencies in cotton (Gossypium hirsutum L.) have recently been reported in many parts of the Cotton Belt. Foliar K sprays are sometimes used to correct these mid-season deficiencies. However, little is known about the uptake of K by leaves, whether spray adjuvants or surfactants facilitate movement of K into leaves, or whether foliar-applied K plus adjuvants enhance lint yield. The objective of this study was to compare the efficacy of spray adjuvants when mixed with foliar potassium nitrate (KNO3) solutions. Three field experiments (one K concentration time-course study and two foliar-applied K lint yield studies) were conducted. In the time-course study, plants were sprayed over-the-top once during mid-bloom with a 11.2 kg KNO3/ha (4.3 kg K/ha). Leaf blade and petiole K concentration were monitored at 0, 2, 4, 6, 24, and 48 h after application. The KNO3 solutions were applied alone or with either Tween 20 (a commonly used laboratory surfactant), Kinetic, Dyne-amic, Penetrator Plus, Invade, Plex, or X-77. Water and an unsprayed check were also evaluated. Applying KNO3 with any of the tested adjuvants resulted in higher leaf blade K concentration at 4 h after application (14.9 g/kg) compared to KNO3 sprays without an adjuvant (13.0 g/kg). At 24 h, leaf blades treated with KNO3 without adjuvant had higher K concentration (13.7 g/kg) than the water and check treatments (12.8 g/kg). Petiole K averaged 47 g/kg and was unaffected by the treatments. For the first lint yield study, plots received foliar-applied KNO3 (at a seasonal rate of 44.8 kg/ha) with one of four selected adjuvants or a Tween 20 solution without KNO3. For the second lint yield study, plots received foliar-applied KNO3 (at seasonal rates of 0, 22.4, and 44.8 kg/ha) with or without Penetrator Plus. Water as a foliar spray and an unsprayed check were also included. In both years, foliar-applied K increased leaf blade K concentration but lint yields and fiber properties were not affected. In summary, leaf blade K concentrations increased when adjuvants were added to the foliar-applied K solutions but these increases did not result in greater lint yield.
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