RESPONSE OF NITROGEN FERTILIZATION ON BT AND NON-BT COTTON (Gossypium hirsutum) HYBRIDS
A field experiment was conducted during 2006 and 2007 (June- December) at New Delhi to assess the performance of three cotton hybrids of which two Bt (MRC 6304 & RCH 317) and one non-Bt cotton hybrid LHH 144 (North zone check) in response to nitrogen fertilization (0, 60, 120 and 180 kg ha -1 ). Based on pooled analysis, both Bt hybrids produced similar seed cotton yield (SCY). Bt hybrid have produced 7.1 bolls/plant (on an average) and bolls 0.48 g heavier than non Bt hybrid LHH 144 that lead to 1.07 t ha -1 higher SCY of Bt hybrids than non-Bt hybrid (1.93 t ha -1 ). Though the N uptake by cotton hybrids was statistically similar N harvest index (NHI) was higher in Bt hybrid (57.85) as compared to non-Bt hybrid (40.5). The agronomic N use efficiency (ANUE) was highest in MRC 6304 Bt (6.44) and least in LHH 144 non-Bt cotton (3.91). Cotton growth, yield attributes, SCY, and N uptake increased with each successive increase to the highest level of 180 kg ha -1 however, the N response of cotton was quadratic in nature with optimum dose of 173.0 kg ha -1 . The NHI decreased with increase in N dose i.e. from the highest of 56.3 in control to the lowest of 48.8 with 180 kg ha -1 N fertilization. ANUE and physiological NUE that was highest with 60 (5.73) and 120 kg N fertilization (17.05), respectively and decreased with further increase in N dose. The cotton hybrid x N interaction effect revealed that Bt cottons have quadratic N response while non-Bt cotton has linear N response. From the economic point of view, Bt hybrids with 120 kg Nha -1 could be optimum dose for cotton cultivation. DOI:  http://dx.doi.org/10.3329/sja.v11i1.18389 SAARC J. Agri., 11(1): 121-132 (2013)
Water Status and Leaf Area Production in Water- and Nitrogen-Stressed Cotton
The combined effects of water and N deficits on leaf area production and water relations in cotton (Gossypium hirsutum L.) have not been investigated thoroughly. A study was conducted to evaluate the responses of leaf area production and water relations in cotton plants exposed to water and N deficits during the preflowering stage. Two N treatments-nutrient solution with 12 mM of N (N-supplied) and N-free nutrient solution (N-starved) -were applied to plants when the third true leaf was visible. Two irrigation treatments - daily irrigation (well watered) and no irrigation (water stressed) - were superimposed on each N treatment once the plants were moved into the test chambers when they reached a leaf area of 0.050 ± 0.002 m 2 . Leaf area and leaf water and osmotic potentials were measured at the end of each day-time period. Under well-watered conditions, leaf turgor potential in N-starved plants was about 0.3 kJ kg -1 lower than in N-supplied plants. When plants were exposed to water deficits, the decline of leaf water potential relative to soil water content was greater in N-starved plants than in N-supplied plants. Nitrogen deficiency delayed and decreased the magnitude of osmotic potential adjustment and, therefore, reduced the capacity of leaves to maintain turgor. Water and N deficits decreased whole-plant cumulative leaf area about 50 and 40%, respectively, through decreased daily production of mainstem and branch leaves and decreased final area of individual mainstem and branch leaves. Nitrogen deficiency induced a higher sensitivity of leaf growth inhibition to water deficits.
The etiology and surgical management of tracheal collapse in calves.
The mean ages of 10 calves with tracheal collapse were 2.7 weeks at onset of clinical signs and 9.4 weeks at presentation for treatment. Inspiratory and expiratory dyspnea and stunted growth were the most common clinical signs. There were abnormalities of the cranial ribs consistent with healing fractures with redundant callus in eight lateral thoracic radiographs. Tracheal collapse in calves may result from cranial thoracic trauma during or soon after birth. Short polypropylene ring prostheses made from 60 ml syringe barrels were placed on the tracheas of four calves with cervical tracheal collapse. There were cranial rib masses in all calves and resection of the right first and second ribs was necessary in one calf to allow placement of prostheses. Dyspnea was relieved in all calves. One calf died of unrelated causes in year 3, and one calf had recurrence of clinical signs at month 5 and was euthanatized. In both calves, tracheal stenosis resulted from continued growth and infolding of the trachea within the constraints of the prostheses. One calf was alive at month 11, and one calf died of acute bronchopneumonia on day 2. Removal of tracheal prostheses in calves is recommended after 2 to 3 months if clinical signs recur.