Understanding the impact that climatic factors have on cotton production may help physiologists to determine possible control mechanisms which influence the flowering of cotton plants. This study was conducted to investigate the nature of the effects of climatic factors prevailing prior and subsequent to either flowering or boll setting on flower and boll production and retention in Egyptian cotton Gossypium barbadense L. Two uniform field trials using the cotton cultivated variety Giza 75 were carried out at the Agricultural Research Center, Giza, Egypt. Randomly chosen plants were used to record daily numbers of flowers and bolls during the production stage (68 d in Season I and 62 d in Season II). The daily records of the climatic factors (air temperature, diurnal temperature range, evaporation, soil surface temperature, sunshine duration, and humidity) were recorded during the entire period of production and also for the 15 d periods before and after anthesis. The effects of climatic factors on flower and boll production were quantified in non-limiting management techniques. Relationships in the form of simple and multiple correlations were computed between climatic factors and flower and boll production and retention. The data indicated that evaporation, minimum humidity and sunshine duration were the most effective climatic factors during preceding and succeeding periods on boll production and retention. There was a negative correlation between flower and boll production and either evaporation or sunshine duration, while the same correlation with minimum humidity was positive. Thus, it appeared that low evaporation rate, reduced sunshine duration and high humidity would enhance flower and boll formation. Accordingly, the deleterious effects of climatic factors on cotton production could be minimized through applying appropriate production practices, which would control and adjust the impact of these factors and thus potentially lead to an important improvement in cotton yield in Egypt.KEY WORDS: Boll retention · Evaporation · Flower and boll production · Humidity · Sunshine duration · TemperatureResale or republication not permitted without written consent of the publisher

Efecto de la fertilización con potasio y de la aplicación foliar de zinc y fósforo en el rendimiento de aceite y proteína y en las propiedades del aceite de algodón. Para maximizar la cantidad y calidad del valor nutricional de una semilla en términos de ácidos grasos y proteínas es necesario identificar los factores que los afectan y proponer métodos que favorezcan los resultados deseados a través de cambios o mejoras en las prácticas utilizadas. Los experimentos se llevaron a cabo en dos campañas sucesivas en el Agricultural Research Center, Giza, Egipto, en el cultivo "Giza 86" (Gossypium barbadense L.) para estudiar los efectos de la fertilización con potasio (a 0.0 y 47.7 kg por ha) y las aplicaciones foliares de zinc (a 0.0 y 57.6 g por ha, dos veces, 70 y 85 días después de la plantación) y fósforo (a 0.0, 576, 1152, y 1728 g por ha, dos veces, 80 y 95 días después de la plantación). La aplicación del potasio junto con la pulverización de las plantas con zinc y fósforo causó un incremento en el rendimiento del algodón, el índice de semilla, el contenido graso, los rendimientos de aceite y proteína, el contenido de materia insaponificable en el aceite y el contenido total de ácidos grasos insaturados (oleico y linoleico). Por el contrario estos tratamientos disminuyeron el índice de acidez, el índice de saponificación y el contenido de ácidos grasos saturados. La mayor concentración de fósforo produjo los mejores rendimientos de algodón, de índice de semilla, de los rendimientos de aceite y proteína, y de materia insaponificable en el aceite.

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Field experiments were conducted during two successive seasons in the Agricultural Research Center, Giza, Egypt (a clay loam soil), to study the effects of phosphorus fertilization (addition at rates of 44 and 74 kg of P # O & \ha) and foliar application of zinc (at 0n0 and 40 ppm of Zn applied twice, 75 and 90 days after planting) and calcium (at 0n0, 20, 40, and 60 ppm of Ca applied twice, 80 and 95 days after planting) on seed, protein and oil yields and oil properties of the Egyptian cotton cultivar Giza 75. Application of P at the high rate and spraying plants with zinc and calcium at any concentration increased cottonseed yield\ha, seed index, seed oil content, oil and protein yields\ha, seed oil unsaponifiable matter, and total unsaturated fatty acids (oleic and linoleic). Conversely, decreases in oil acid value, saponification value and total saturated fatty acids occurred. The seed protein and oil refractive index tended to increase when the high P rate and Zn were applied. Seed protein content tended to decrease slightly with Ca application. Regardless of the slight decrease in protein content as a result of Ca application, the yield of protein increased, due to the fact that there was an obvious increase in seed yield which counterbalanced the negative effect of the decrease in protein content. The highest Ca concentration (60 ppm) gave the highest values of cottonseed yield\ha, seed index, seed oil and protein yields\ha and oil unsaponifiable matter, followed by the concentration of 40 ppm. The concentration of 40 ppm gave the lowest total saturated fatty acids. The effect of Ca concentrations on oil refractive index was very limited.

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RESUMENEfecto del nitrógeno, potasio y retardantes del crecimiento de plantas sobre el contenido en aceite y sobre la calidad de la semilla de algodón El objetivo de los experimentos de campo fue investigar el efecto del nitrogeno, potasio y retardantes del crecimiento de plantas sobre el contenido en proteínas y aceite de una semilla de algodón cultivada en Egipto (Gossypium barbadense Giza 86). Los tratamientos consistieron en la aplicación en suelo de N (95 and 143 kg N ha Ϫ1 en forma de nitrato amónico), aplicación foliar de K (0, 319, 638 or 957 g K ha Ϫ1 como sulfato potásico) y aplicación foliar de cloruro de m mepiquat (MC) (0 and 48 + 24 g de ingrediente activo ha Ϫ1) sobre un cultivar de algodón «Giza 86» (Gossypium barbadense). La aplicación de la cantidad más elevada de N, unida a la aplicación de potasio y del retardador MC, aumentó significativamente el rendimiento en semilla, así como el contenido en proteinas y en aceite. Respecto al aceite, aumentó el índice de refracción, la fracción insaponificable y el contenido total en ácidos insaturados (oleico y linoleico). Por el contrario, la acidez del aceite y su índice de saponificación disminuyó con la aplicación foliar de K y MC. El contenido en aceite de la semilla disminuyó cuando sólo se aplicó N. PALABRAS-CLAVE: Aceite de semilla -Ácidos grasosAlgodón -Cloruro de mepiquat -Nitrógeno -Potasio -Proteina. SUMMARYNitrogen, potassium and plant growth retardant effects on oil content and quality of cotton seedThe aim of this field experiment was to investigate the effect of nitrogen, potassium and a plant growth retardant (PGR) on seed yield and protein and oil content of an Egyptian cotton cultivar (Gossypium barbadense Giza 86). Treatments consisted of: soil application of N (95 and 143 kg N ha Ϫ1 in the form ammonium nitrate), foliar application of potassium (0, 319, 638 or 957 g K ha Ϫ1 as potassium sulfate) and foliar application of mepiquat chloride (MC) (0 and 48 + 24 g active ingredient ha Ϫ1) on seed, protein and oil yields and oil properties of Egyptian cotton cultivar "Giza 86" (Gossypium barbadense). After applying the higher N-rate, foliar application of potassium and plant growth retardant MC significantly increased seed yield and the content of seed protein and oil, seed oil refractive index, unsaponifiable matter and total unsaturated fatty acids (oleic and linoleic). In contrast, oil acid and saponification value as well as total saturated fatty acids were Nitrogen, potassium and plant growth retardant effects on oil content and quality of cotton seed decreased by foliar application of potassium and MC. The seed oil content was decreased with soil application of N.

The increase in the population in Egypt makes it imperative to explore promising approaches to increase food supply, including protein and oil, to meet the needs of the Egyptian people. Cotton is the principal crop of Egyptian agriculture. It is grown mainly for its fiber, but cottonseed products are also of economic importance. Cottonseed is presently the main source of edible oil and meal for livestock in Egypt. Field experiments were conducted in two successive seasons at the Agricultural Research Center (Giza, Egypt) on cotton (Gossypium barbadense L. cv. Giza 75) to determine the effect of nitrogen (N) fertilizer rate (107 and 161 kg of N/ha applied as ammonium nitrate containing 33.5% N in two equal doses at 6 and 8 wk after sowing), together with foliar applications of plant growth retardants (mepiquat chloride "Pix," chloromequat chloride "Cycocel," and daminozide "Alar," each applied once at 288 g active ingredient/ha, after 75 d from sowing) and zinc (Zn) (applied in chelated form after 80 and 95 d from sowing at 48 g of Zn/ha) on seed, protein and oil yields and oil properties of cotton. The higher N-rate, as well as the application of all growth retardants and Zn, resulted in an increase in cottonseed yield, seed protein content, oil and protein yields/ha, seed oil refractive index, unsaponifiable matter, and total unsaturated fatty acids (oleic and linoleic). These treatments tended to decrease oil acid value, saponification value, and total saturated fatty acids. The seed oil content tended to decrease as N-rate increased and increased with the application of all growth retardants and Zn. There were some differences between Pix, Cycocel, and Alar regarding their effects on the studied characters. The highest increase in seed, oil, and protein yields/ha was found with Pix, followed by Cycocel. The Cycocel treatment gave the lowest total saturated fatty acids oil content, followed by Alar.