GB2073590A - Harvesting pretreatment - Google Patents

Abstract

An improved method of desiccating crops of oil-seed rape with diquat, wherein the diquat is applied in admixture with di-l-p-menthene, resulting in reduced losses of seed from the desiccated seed-heeds of the crop.

Description

SPECIFICATION Improved harvesting pre-treatment This invention relates to the harvesting of oil-seed rape [Various species of this plant are grown commercially (for example Brassica campestris and Brassica rapusJ.

Oii-seed rape is usually harvested by means of a combine harvester machine. The seed is separated from the seed-pods and stems by a threshing procedure. The threshing operation is facilitated if the crop is in a dry condition rather than green and moist.

Because of the variability of climatic conditions the crop does not always reach a suitably dry condition at a convenient time for harvest. It is therefore sometimes convenient to apply a desiccating agent to the crop before harvest, so as to bring it into a suitable state of dryness. A material commonly used for this purpose is the herbicide and desiccating agent commercially available under the Registered Trade Mark "Reglone". "Reglone" comprises an aqueous solution of a salt of diquat. Diquat is the common name for the 1,1' - ethylene - 2,2 - bipyridylium ion, having the structural formula (I)

In order to balance the two positive charges on the 1,1' - ethylene - 2,2' - bipyridylium ion, an appropri ate number of counter-ions must be present, for example two halide anions.Diquat is commercially available as its dibromide salt; other salts, such as diquatdichloride may, however, be prepared. Since the characteristic biological effect of a diquat salt is due to the diquat part of the molecule it is customary to quote concentrations of active ingredient and rates of application in terms of the amount of diquat used, thus avoiding the inconvenience of having to quote different rates of application for different salts of diquat. Unless otherwise stated, application rates and concentrations quoted in this specification therefore relate to the amount of diquat and not of diquat salt.

A difficulty which is encountered when harvesting oil-seed rape, whether the seed pods have dried out naturally orwhetherthey have been dried by appli cation of a desiccant, is that the dried seed-pods are liable to shatter ahead of the cutter bar when dis turbed by the harvester, so that a proportion of the seed is not collected by the harvesting machinery and is lost. Furthermore, once a crop has been tre ated with a desiccating agent, it becomes extremely vulnerable to shattering of the dried seed-pods by wind or heavy rain. If bad weather intervenes bet ween desiccation and harvest, much of the crop may therefore be lost. A method of reducing the possibil ity of such losses following the application of diquat has now been devised.

According to the present invention there is provided a process of reducing seed loss from crops of oil-seed rape desiccated by treatment with diquat which comprises applying the diquat in admixture with di-l-p-menthene. Di-l-p-menthene has the structural formula (II)

It is a commercially available material derived from 6-pinene, a constituent of pine turpentine.

The mechanism by which the di-l-p-menthene reduces seed loss is not understood. It is believed that the di-l-p-menthene may polymerise upon exposure to daylight to form a film over the surface of the plants to which it is applied. However it is considered unlikelythatthe film would have sufficient mechanical strength to prevent seed pods from shattering. It is though that the natural process of splitting ("shattering") of the dry seed pod is brought about by variation in the moisture content of the pod in response to daily variations in atmospheric moisture. The repeated cycle of absorption and loss of moisture sets up differential stresses in the pod leading to splitting. It is possible that the di-l-p-menthene reduces pod splitting by impeding the movement of moisture into and out of the pod.

Whatever its mode of action may be, however, addition of di-l-p-menthene to diquat has brought about a substantial reduction in seed loss in a field trial in which strong winds and heavy rain intervened between application of the desiccant and harvesting. In the same field trial, significant amounts of seed were lost in a plot treated with diquat alone.

The amount of di-l-p-menthene to be applied in the process of the invention may be varied, but may for example range from 0.5 to 10.0 ml of di-l-pmenthene per gram of diquat applied. The di-l-pmenthene is dispersed in the spray solution containing the diquat, preferably with the aid of a surfaceactive agent. The amount of diquat used for desiccating the oil-seed rape may vary, depending for example on the condition of the crop, but in general will usually be in the range from 2 to 4 pints of 14% diquat solution per acre (159to 318 9 of diquat per acre).

The surface-active agent should preferably be a non-ionic or cationic surface-active agent. Anionic surface-active agents are less preferred since in some cases they may interact undesirable with the diquat present in the composition.

The choice of surface active agent is of course within the knowledge of those skilled in the art. By way of example, however, non-ionic surface active agents useful in the compositions of the invention include the condensation products of ethylene oxide with fatty alcohols such as oleyl alcohol and cetyl alcohol, or with alkyl phenols such as octylphenol, nonylphenol and octylcresol. Other non-ionic agents are the partial esters derived from long chain fatty acids and hexitol anhydrides, for example sorbitan monolaurate; the condensation products of the said partial esters with ethylene oxide; and the lecithins.

Examples of cationic surface active agents include quaternary ammonium salts and condensates of ethylene oxide with primary amines.

The amount of surface-active agent used in the composition is not critical and may be varied considerably. However as a general guide an amount of from 0.5 to 2.0 grams ofsurfactant per gram of diquat, for example 1.0 gram per gram of diquat, is usually convenient.

In another aspect, the invention provides a novel composition comprising an aqueous solution of a diquat salt in admixture with di-l-p-menthene in an amount of from 0.25 ml to 10.0 ml per gram of diquat. The composition may further contain a surface-active agent The composition may for example be a concentrated composition containing for example from 100 to 200 grams per litre of diquat. Such concentrated compositions may conveniently be transported and stored and may be diluted with water at the site where application of the diquat is to take place, so as to provide a suitably dilute spray composition. Typically the diquatwill be applied at a concentration of 0.1-0.2 grams per litre the final spray composition.

The process ofthe invention is illustrated by the following Example.

EXAMPLE Three trial plots in a field of rape (Brassica campestris) situated on a hill in Nottinghamshire, England, were sprayed with the following compositions.

The amounts specified below are sufficient for 1 acre in each case, and would be diluted to a volume of 50 gallons with water for application. In this trial the experimental plots were 10 metres by 100 metres, and proportionally smaller amounts ofthe compositions were therefore prepared. The rest of the field was sprayed with 3 pints of "Reglone" and 8 fluid ounces of"Agral" per acre, diluted to 50 gallons with water.

The gallon measure referred to herein is the British Imperial gallon (4.54 litres).

Composition 1 "Reglone" 3 pints (568 ml) "Agral" 8fluid ounces (226.8 ml) "Miller-Aide" 4 fluid ounces (113.4ml) Composition 2 "Reglone" 3 pints (568 ml) "Agral" 8 fluid ounces (226.8 ml) "Miller-Aide" 12 fluid ounces (340.2 ml) Composition 3 "Reglone" 3 pints (568 ml) "Agral" 8 fluid ounces (226.8 ml) "Miller-Aide" 16 fluid ounces (453 my) "Reglone" is a Registered Trade Mark for an aque ous solution ofdiquatdibromide containing 140 grams of diquat per litre.

"Agral" is a Registered Trade Mark for a surface active agent comprising a condensate of from 7 to 8 molar proportions of ethylene oxide with 1 molar proportion ofp-nonylphenol.

"Miller-Aide" is a Registered Trade Mark for a composition containing 95% of di-l-p-menthene and 5% inert ingredients.

The compositions were applied on 15 August and the crop left unharvested until 14 September. During this period 80% of the crop remained stranding, and high winds and heavy rain occurred. Losses due to shattering of seed pods were estimated to be 1% at moston 13 September. When harvested, losses of seed due to shattering of seed pods atthe cutter bar were vary small. No difficulties were experienced in threshing outthe seed. No differences were observed between the three rates of application of di-l-p-menthene in the prevention of pod-shattering or in the speed or completeness with which the oilseed rapewas disiccated.

In the part of the field treated with "Reglone" only (i.e. without "Milleraide"), losses of seed due to shattering of seed-pods were significant.

Claims (6)

1. A process of desiccating crops of oil-seed rape which comprises applying thereto a composition containing diquat and di-l-p-menthene.

2. A process according to claim 1 wherein the amount of d4-p-menthene applied is from 0.25 to 10.0 millilitres per gram of diquat applied.

3. A process according to claim 1 or claim 2 wherein the amount of di-l-p-menthene applied is from 0.5 to 10.0 millilitres per gram of diquat applied.

4. A desiccating composition comprising an aqueous solution of a salt of diquat in admixture with di-l-p-menthene.

5. A desiccating composition according to claim 4 wherein the diquat is present in a concentration of from 100 to 200 grams per litre.

6. Adesiccating composition according to claim 4 or claim 5 which further comprises a surface-active agent