Effect of nitrogen and zinc fertilization and plant growth retardants on cottonseed, protein, oil yields, and oil properties

Abstract

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.

Cottonseed yield and its quality as affected by mineral fertilizers and plant growth retardants

“…Similar results were obtained by Sarwar Cheema et al [33]. Application of Zn significantly increased seed yield ha −1 (8.44%), as compared with untreated plants [35]. Zeng [53] stated application of Zn to cotton plants on calcareous soil increased yield by 7.8% -25.7%.…”

“…All tested PGR (Pix, Cycocel and Alar) significantly increased seed yield ha −1 (7.79% -12.08%), compared with the untreated control. The most effective was Pix (12.08%), followed by Cycocel (10.57%) [35]. These results may be attributed to the promoting effect of these substances on numerous physiological processes, leading to improvement of all yield components.…”

“…As for the chemical properties considered in the study, the t-test computed in accordance with standard deviation was utilized to verify the significance between treatments means [1]. [35]. Abdel-Malak et al [45] stated that cotton yield was higher when N was applied at a rate of 190 kg·ha −1 than at the rate of 143 kg·ha −1 .…”

“…Seed index significantly increased with increasing N rate ( Table 3) [35]. This may be partially due to enhanced photosynthetic activity [2].…”

“…However, there is limited information about the most suitable management practice for application of N, P, K, Zn, Ca and PGRs in order to optimize the quantity and quality of oil and protein of cottonseed [34]. Due to the economic importance of cottonseed (presently the main source of edible oil and meal for livestock) in Egypt, this study was designed to identify the best combination of these production treatments in order to improve cottonseed, protein and oil yields and oil properties of Egyptian cotton (G. barbadense L.) [1,[35][36][37].…”