Method of Increasing the Yield of Sugar From Sugarcane

This invention relates to a method of increasing the yield of sugar obtained from sugarcane and more particularly relates to a method of increasing the recoverable sugar in sugarcane by treating the sugarcane plant during its maturation with certain esters of 2-[4-(5-trifluoromethyl-2-pyridinyloxy) phenoxy]propanoic acid having a minimum of 10 carbon atoms in the ester moiety.

A variety of plant growth regulators, stimulants and promotors have been tried in the past in attempts to increase the yields of cultivated crops. It has been found that materials that have an effect on one crop will not necessarily have an effect or have a different effect on other crops.

One particular crop which has been given increased attention for the purpose of increasing yields is sugarcane. Accordingly it is an object of the present invention to provide new methods and compositions of increasing the yield of sugar obtained from sugarcane.

It has now been found that the recovery of sugar from sugarcane can be significantly increased by the use of certain esters. Consequently it has now been found that it is possible to increase the recoverable sugar in sugarcane by contacting the sugarcane plant with an effective amount of an ester of the following propanoic acid: ##STR2## wherein R is an alkyl group having from 10 to 16 carbon atoms.

The compounds useful in the present method can be readily prepared by known esterification procedures. Thus the corresponding propanoic acid chloride of the structural formula: ##STR3## is reacted with an alkanol of from 10 to 16 carbon atoms using standard esterification procedures i.e., heating in an inert solvent in the presence of an acid scavenger. The following example demonstrates the preparation of the desired propanoic esters.

n-Dodecanol(2.5 grams; 0.134mol), toluene (80 ml) and triethylamine (5 ml) were placed into a 300 ml, 3-necked glass reaction flask equipped with stirrer, thermometer, reflux condenser, and nitrogen line. 2-[4-(5-trifluoromethyl-2-pyridinyloxy)phenoxy]propanoic acid chloride (4.45 grams; 0.0125 mol) in toluene (30 ml) was added dropwise to the reaction mixture with stirring at a temperature of about 10.degree. C. The temperature of the reaction mixture was allowed to rise to room temperature and stirred overnight.

The reaction mixture was transferred to a separatory funnel, washed with water (100 ml); then with sodium bicarbonate (5%, 100 ml). Then the reaction mixture was divided and the toluene stripped resulting in a light yellow oil (6.5 grams).

This oil was chromatographed into 8 fractions through florisil (150 ml). Fractions 2-5 were combined as a clear oil. Infrared analysis was consistent with the desired product.

Elemental analysis of the product was as follows:

Other alcohols that are useful in the preparation of the compounds of this invention are n-undecanol, n-tridecanol, n-tetradecanol, n-pentadecanol, n-hexadecanol, n-heptadecanol, and n-octadecanol. The products made from these alcohols by reaction with the compound of structure II are:

n-undecyl 2-[4-(5-trifluoromethyl-2-pyridinyloxy)phenoxy]propanoate

n-tridecyl 2-[4-(5-trifluoromethyl-2-pyridinyloxy)phenoxy]propanoate

n-tetradecyl 2-[4-(5-trifluoromethyl-2-pyridinyloxy)phenoxy]propanoate

n-pentadecyl 2-4-(5-trifluoromethyl-2-pyridinyloxy)phenoxy]propanoate

n-hexadecyl 2-[4-(5-trifluoromethyl-2-pyridinyloxy)phenoxy]propanoate

n-heptadecyl 2-4-(5-trifluoromethyl-2-pyridinyloxy)phenoxy]propanoate

n-octadecyl 2-[4-(5-trifluoromethyl-2-pyridinyloxy)phenoxy]propanoate

The effectiveness of the compounds of this invention for increasing the recoverable sugar from sugarcane was demonstrated in a field test by applying a solution in acetone diluted for application to sugarcane at the various indicated application rates. The test compound was applied at the test rate on the spindle area of each of 20 stalks of sugarcane in a field in Hawaii, using a syringe with a fine needle as the applioator. A set of 10 of these treated stalks from each group was harvested at 4 and 8 weeks after such treatment. In each harvest a set of 10 untreated stalks were also harvested as a control.

The top 14 joints of the treated cane as well as those of the controls were removed, combined and analyzed for juice purity and pol percent cane, following the "press method" developed and described by T. Tanimoto, Hawaiian Planters Record, 57, 133 (1964). Pol percent cane is a polarimetric determination and equals the percentage of sucrose if the latter is the only substance in the solution which will rotate the plane of polarized light. The pol percent cane is a standard method of determining the sucrose content of sugarcane.

In the use of these compounds to increase the recoverable sugar in sugarcane, sugarcane is treated at a late stage of development of the sugarcane wherein most of the sugar formation takes place. Thus, under normal growing conditions and common cultivation practices the active compounds of this invention can be applied to the sugarcane during the period of from about 2 to 10 weeks before harvesting.

The amount of active compound required to effectively increase the recoverable sugar from sugarcane can vary somewhat depending on such factors as the time of application, the weather, crop density, method of application and the like. Generally, an amount of at least 0.1 pounds per acre and preferably an amount of from 0.1 pounds per acre to about 10 pounds per acre can be used. While an amount greater than those mentioned can be used, they will not result in an advantage that would warrant their expense and are, therefore, not practical.

For practical use in treating sugarcane, the active compounds of this invention are generally incorporated into compositions or formulations which comprise an inert carrier and an effective amount of the compound. The compositions enable the active compound to be conveniently applied to the sugarcane at the desired rate. The formulations can be liquid formulations such as emulsifiable concentrates or solutions or solid formulations such as dusts, granules or wettable powders.

The preferred compositions are liquid formulations, particularly solutions or emulsifiable concentrates. Emulsifiable concentrates comprise the active compound, according to this invention, and as the inert carrier, a solvent and an emulsifier. Such emulsifiable concentrates can be extended with water and/or oil to any desired concentration of active compound for application as sprays to the sugarcane. The emulsifier most commonly used in these concentrates are nonionic or mixtures of nonionic with anionic surface-active agents. With the use of some emulsifier systems an inverted emulsion (water-in-oil) can be prepared.

Typical formulations according to the present invention useful for increasing the recoverable sugar in sugarcane are illustrated in the following examples wherein the quantities are given in parts by weight.

The following ingredients are blended thoroughly until a homogeneous liquid concentrate is obtained. This concentrate is mixed with water to give an aqueous dispersion containing the desired concentration of the active ingredients for use as a spray.

The following components are mixed intimately in conventional mixing or blending equipment and are then ground to a powder having a particle size of less than about 50 microns. The finished powder is dispersed in water to give the desired concentration of active compound for application to the sugarcane.

The following ingredients are mixed thoroughly and are then ground to an average particle size of less than about 50 microns to give a dust suitable for application with conventional dusting equipment.