Abstract
A field experiment was conducted on cotton varieties NIAB-78 and NIAB-86 for exploring the possibilities of ameliorating the adverse effect of flower and boll shedding on yield of seed cotton through supplemental N application. Complete flower shedding was simulated by removing all the flowers and bolls manually on August 28 and September 12. Additional N qiti 25 kg/ha was applied immediately after deflowering.
The results indicated that supplemental N had no beneficial effect on yield of seed cotton. The recovery of seed cotton after deflowering in August (28th) was 77.5 and 72.4% in N1AB-78 and NIAB-86 under control, respectively. With 1(X) kg N/ha application, the recovery of seed cotton was 84.8 and 77.1% of that under normal standard treatments in N1AB-78 and NIAB-86, respectively. Deflowering in September (12th) drastically reduced the yield of seed cotton; N1AB-78 produced 48% and NIAB-86 produced 55% seed cotton as compared to their respective stan-dards,
INTRODUCTION
The flower and boll shedding in cotton is a normal and natural phenomenon, per-haps, desirable and certainly unavoidable. Frequently, 25 to 50% of all the flower buds (squares) formed by the plant abscise before blossoming (Hall, 1958). Though there is evidence that in some locations square ab-scission may riot affect yield potential (Gutierrez el at, 1977) while at other loca-tions 25% square shedding may be sufficient to reduce yield or delay maturity. Guinn and Isilauney (1984) found boll retention to de-crease with increased boll load and sug-gested increased competition for nutrients by the plants.
It may be difficult to assign reasons for the abscissions and thus to develop strate-gies to correct it. Guinn 0982) listed 13
causes of square and boll abscission. These may be grouped in two categories: 1) Inter-nal, physiological stresses brought about by shortage or excess of moisture, light or nu-trients; and 2) external damage to the or-gans due to attack by insects or micro-or-ganisms.
The purpose of this study was to ex-plore the possibilities of ameliorating the adverse effect of excessive flower and boll shedding on the yield of cotton varieties NIAB-78 and NIAB-86 by applying supple-mental nitrogen after lower shedding.
