HERBICIDAL COMPOSITIONS

Abstract

The invention is method of combatting weeds, which comprises applying to a soil region an herbicidal combination comprising: at least one alkali metal compound selected from alkali hydroxide, alkali carbonate and alkali bicarbonate; and at least one calcium compound selected from calcium hydroxide and calcium bicarbonate; such that the predominant component of the combination is(are) the alkali metal compound(s). Herbicidal formulations are also provided by the invention.

Claims

1. A method of combatting weeds, which comprises: applying to a soil region an herbicidal combination comprising: at least one alkali metal compound selected from alkali hydroxide, alkali carbonate and alkali bicarbonate; and at least one calcium compound selected from calcium hydroxide and calcium bicarbonate; such that a predominant component of the combination is the at least one alkali metal compound.

2. A method according to claim 1, wherein the herbicidal combination comprises sodium hydroxide, potassium hydroxide and calcium hydroxide.

3. A method according to claim 1, wherein the herbicidal combination comprises sodium hydroxide, potassium hydroxide and calcium bicarbonate.

4. A method according to claim 1, wherein a weight ratio of the at least one alkali compound to the at least one calcium compound is in the range from 10:1 to 1.5:1.

5. A method according to claim 4, wherein the herbicidal combination comprises sodium hydroxide, potassium hydroxide and calcium hydroxide at weight proportions in the range from 5:1 to 1.5:1 of [NaOH+KOH]:Ca(OH).sub.2, with the alkali hydroxides NaOH : KOH being proportioned in the range from 5:1 to 1:5.

6. A method according to claim 4, wherein the herbicidal combination comprises sodium hydroxide, potassium hydroxide and calcium bicarbonate at weight proportions in the range from 5:1 to 1.5:1 of [NaOH+KOH]:Ca(HCO.sub.3).sub.2, with the alkali hydroxides NaOH:KOH being proportioned in the range from 5:1 to 1:5.

7. A method according to claim 5, wherein the weight proportion [NaOH+KOH]:Ca(OH).sub.2 or the weight proportion [NaOH+KOH]:Ca(HCO.sub.3).sub.2 is from 5:1 to 3:1, with the alkali hydroxides NaOH:KOH being proportioned in the range from 3:1 to 1:1.

8. A method according to claim 5, wherein the weight proportion [NaOH+KOH]:Ca(OH).sub.2 or the weight proportion [NaOH+KOH]:Ca(HCO.sub.3).sub.2 is from 3:1 to 1.5:1, with the alkali hydroxides NaOH:KOH being proportioned in the range from 3:1 to 1:1.

9. A method according to claim 1, for controlling glyphosate-resistant species.

10. A method according to claim 1, devoid of simultaneous application of an organic herbicide.

11. A method according to claim 1, wherein the herbicidal combination is applied to keep an area around railways free from vegetation.

12. A method according to claim 1, wherein the herbicidal combination is applied to control weeds in an agricultural area to be seeded or planted.

13. A method according to claim 1, wherein the herbicidal combination is applied as a mixed composition of the individual components in a sprayable solution or suspension containing from 10 g to 250 g of the alkaline compounds per liter water.

14. A method according to claim 1, wherein the herbicidal combination is applied as a mixed composition of the individual components in a solid form.

15. Herbicidal formulation comprising sodium hydroxide, potassium hydroxide and at least one alkaline calcium compound, at weight mixing ratios varying in the range from 30:1 to 1.5:1 of [NaOH+KOH]:calcium compound, with the alkali hydroxides NaOH:KOH being proportioned in the range from 5:1 to 1:5.

16. Herbicidal formulation comprising sodium hydroxide, potassium hydroxide and at least one alkaline calcium compound according to claim 15, at weight mixing ratios varying in the range from 5:1 to 3:1 of [NaOH+KOH]:calcium compound, with the alkali hydroxides NaOH:KOH being proportioned in the range from 3:1 to 1:1.

17. The herbicidal formulation according to claim 15, wherein the alkaline calcium compound is calcium hydroxide or calcium bicarbonate.

18. The herbicidal formulation according to claim 15, in the form of aqueous concentrate comprising sodium hydroxide and potassium hydroxide in a total amount from 300 to 480 g, and in addition, not less than 10 g of the alkaline calcium compound per 1 liter of water.

19. The herbicidal formulation according to claim 15, in a solid form.

20. The herbicidal formulation according to claim 16, wherein the alkaline calcium compound is calcium hydroxide or calcium bicarbonate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1A and FIG. 1B are photos of planters in which grass was grown, taken at t=0 and t=30 days, respectively.

[0037] FIG. 2A and FIG. 2B are photos taken at t=60 days, of a control (nontreated) planter (2A) and a planter treated with an aqueous composition of the herbicidal combination (2B).

[0038] FIG. 3A and FIG. 3B are photos taken at t=60 days, of a control (nontreated) planter (3A) and a planter treated with solid composition (tablet formulation) of the herbicidal combination.

[0039] FIG. 4 is a photo showing rail sleepers. Left: reference rail sleeper. Right: a rail sleeper immersed in the aqueous alkaline composition of the herbicidal combination.

EXAMPLES

Example 1

Preparation of Aqueous Concentrate Formulation of NaOH/KOH/Ca(OH).SUB.2

[0040] The solid materials (NaOH/KOH/CaOH.sub.2) were added to 100 L barrel, followed by addition of water to reach the saturation limit, ˜48%, of the alkali hydroxides. That is, a total of 480 g of NaOH/KOH (300 g NaOH+180 g KOH) and 120 g Ca(OH).sub.2 in 1 liter of water, such that the mixing ratios are 5:3:2 by weight. A suspension was formed (the amount of Ca(OH).sub.2 exceeded the saturation limit), which was stirred for 10-15 minutes with an industrial vertical agitator (100 rpm, Blossom LTD).

[0041] The aqueous concentrate was diluted prior to use by addition of water in a spray tank down to the working concentrations set out in Examples 4 and 5 to afford a sprayable suspension employed in the field experiments reported hereinbelow.

Example 2

Preparation of Water Dispersible Tablet Formulation Of Naoh/Ca(Oh).SUB.2

[0042] A mixture consisting of the NaOH/Ca(OH).sub.2 powders (2:1 weight ratio) was blended and homogenized in a solid homogenizer. The blend was compressed in a tablet press (JM16, under pressure of to 320 kg) to produce tablets (˜13 mm diameter). The tablets were mechanically strong and well-dispersible in water. These NaOH/Ca(OH).sub.2 (2:1) tablets were used in the experiment reported in Example 3.

[0043] By a similar procedure, a blend consisting of a ternary combination, NaOH/KOH/CaOH.sub.2 (5:3:2), is formed into tablets.

Example 3

Weed Control: Experiment in Planters

[0044] 20 L planters were each filled with a mixture of approximately 15 L of soil and a fertilizer. Seeds of grass (paspalum grass) were planted in the planters. The grass was grown during one month with irrigation by an automatic system. Photos taken at the beginning of the experiment and at the end of the one-month growth period are shown in FIG. 1. The planters were then divided into three groups: reference (no treatment), A and B.

[0045] Group A: at the end of the month growth period, an aqueous composition comprising 10 g sodium hydroxide and 5 g calcium hydroxide in 1 L of water (in the form of a milky suspension, owing to insolubility of Ca(OH).sub.2) was applied onto each of the planters. The progress of the treatment was evaluated by visual inspection during an additional month. Photos taken at the end of two-month period (one-month treatment) are shown in FIG. 2B, compared to the reference (2A), indicating efficient weed control.

[0046] Group B: at the end of the month growth period, tablets consisting of mixed sodium hydroxide/calcium hydroxide (2:1) as prepared in Example 2 were added to the planters (the total amounts of the added hydroxides in each planter were 10 g and 5 g, respectively). The progress of the treatment was evaluated by visual inspection during an additional month. Photos taken at the end of two-month period (one-month treatment) are shown in FIG. 3B, compared to the reference (3A), indicating efficient weed control.

[0047] Additionally, wastewater of both treatments was collected. pH was measured, and GC-FID analysis was used for the detection of organic matter. It was found the wastewater pH was below 8. No organic leftovers were detected in the wastewater and water salinity was in the normal range.

Example 4

Weed Control: Small Scale Field Experiment

[0048] A weedy field was divided into 1 m×1 m plots, labeled 1-A to 1-N, 2-O to 2-P and 3-Q to 3-V. Aqueous compositions which contain either one, two or three components dissolved/suspended in water were applied to plots 1-A to 1-N, 2-O to 2-P and 3-Q to 3-V, respectively. The active components(s), the concentration of the dissolved/suspended active components in the aqueous composition (C, expressed as % by weight of the composition) and the mixing ratios in case of multiple components are tabulated in Table 1.

TABLE-US-00001 TABLE 1 Active C Mixing ratio 5 12 30 Ca/K component(s) (%) (% by weight) days days days pH Value Sal. Single-Component Aqueous Compositions (comparative) 1-A NaOH 50 100 C B B+ 8> ND ND 1-B Na.sub.2CO.sub.3 16 100 E D C 8> ND ND 1-C NaHCO.sub.3 9 100 D D+ C 8> ND ND 1-D KOH 50 100 C B B+ 8> ND ND 1-E K.sub.2CO.sub.3 50 100 D C B 8> ND ND 1-F KHCO.sub.3 32 100 D C C+ 8> ND ND 1-G Ca(OH).sub.2 1 100 D D D+ 7  ND ND 1-H CaCO.sub.3 1 100 E E E 7  ND ND 1-I Ca(HCO.sub.3).sub.2 16 100 D D+ C 8> ND ND 1-J Mg(OH).sub.2 1 100 E E E 7  ND ND 1-K MgCO.sub.3 1 100 E E E 7  ND ND 1-L Mg(HCO.sub.3).sub.2 1 100 E E E 7  ND ND 1-M Goal ® 10 100 D C B 7  NR ND 1-N Roundup ® 10 100 D C A* 7  NR ND Two-Component Aqueous Compositions (of the invention) 2-O KOH/Ca(OH).sub.2 10 80 20 C B B+ 8> ND ND 2-P NaOH/Ca(OH).sub.2 5 67 33 C C B 8> ND ND Three-Component Aqueous Compositions (of the Invention) 3-Q NaOH/KOH/ 1.5 50 30 20 B B+ A 8> ↑ ND Ca(HCO.sub.3).sub.2 3-R NaOH/KOH/ 1.5 50 30 20 C B+ A 8> ↑ NC Ca(OH).sub.2 3-S NaOH/KOH/ 1.5 30 30 40 C B+ B+ 8> ↑ NC Ca(OH).sub.2 3-T NaOH/KOH/ 1.5 40 30 30 C B+ B+ 8> ↑ NC Ca(OH).sub.2 3-U NaOH/KOH/ 5 50 30 20 B A ND 8> ↑ NC Ca(OH).sub.2 3-V NaOH/KOH/ 22 50 30 20 A ND ND 8> ↑ NC Ca(OH).sub.2

[0049] Compositions 1-A to 1-L, 2-O, 2-P and 3-Q to 3-V were prepared by dissolving water-soluble powders or pellets in water, or adding to water sparingly soluble powders, or combination of both, at the concentrations set out in Table 1, to form sprayable solutions/suspensions.

[0050] Compositions 1-M and 1-N are based on commercial herbicides available in the market (Roundup Ultra®max/Roundup® full ii (Cuidado Ltd) and Goal® herbicide (Dow Ltd.) diluted to the concentrations set out in Table 1).

[0051] The herbicidal compositions were sprayed at rate of application of 100 liter per hectare.

[0052] The herbicidal effect was determined 5, 12 and 30 days after the treatment. To this end, five categories were defined:

[0053] A category: complete control of the weeds was achieved.

[0054] B category: severe damage was caused to the weeds.

[0055] C category: some damage was caused to the weeds.

[0056] D category: minor damage was caused to the weeds.

[0057] E category: no damage was caused to the weeds.

[0058] The results set out in Table 1 indicate that of the individually applied active compounds, only Glyphosate (the active material of Roundup®) achieved complete weed control, 30 days after the treatment (I-N), with the survival, of course, of glyphosate-resistant weeds (hence A* category—see discussion below). As to the alkaline compounds, it is seen that calcium hydroxide and calcium bicarbonate demonstrate poor activity. Highly concentrated (nearly saturated) alkali metal compounds produce herbicidal effect but are no match for Roundup® (1A-1L).

[0059] Binary combinations consisting of alkali hydroxide/Ca(OH).sub.2 are able to inflict severe damage to the weed when applied at fairly low amounts (2-O and 2-P). That is, it is possible to reduce the applied amounts of the alkaline agents and still achieve acceptable effect when such binary combinations are used.

[0060] Enhanced activity is demonstrated by ternary combinations consisting of sodium hydroxide, potassium hydroxide and calcium hydroxide (or calcium bicarbonate). The 5:3:2 combinations achieved complete weed control faster than Roundup® at surprisingly low amounts of the individual components (3-Q, 3-R, 3-U and 3-V). The 3:3:4 and 4:3:3 combinations were also effective. Additionally, getting new grass to grow in plots treated with such combinations, e.g., plots 3-S and 3-T, met with difficulties and resulted in poor quality grass, indicating that the alkaline calcium compound accounts for a prolonged effect.

[0061] Furthermore, species which survived the Roundup® treatment in the 1-N plot were identified (Vitex cymosa, Conyza sumatrensis, Digitaria insularis, Euphorbia heterophylla and Bidens subaltern). These glyphosate-resistant weeds did not survive in the 3-Q, 3-R, 3-U and 3-V plots after the treatment with the ternary combinations of the invention. Interestingly, an attempt to augment the effect of 2.5% by weight Roundup® sprayable solution by addition of equal amount of the NaOH/KOH/Ca(OH).sub.2 herbicide (i.e., 2.5% by weight, mixing ratio of the hydroxides 5:3:2) did not produce significant improvement.

[0062] 30 days after the treatment, various properties of the soil were measured, as appropriate. pH was nearly neutral or weakly alkaline. The salinity (abbreviated Sal.) of the soil did not change (determined by extraction and titration with KCl). The ratio Ca/K in the soil increased, as indicated by the upward pointing arrow. (ND: not determined; NC: no change).

Example 5

Weed Control: Large Scale Field Experiment

[0063] The herbicidal combination emerging as a promising candidate for weed control based on the results of the field experiment reported in Example 4, namely, NaOH/KOH/Ca(OH).sub.2 (5:3:2) was tested and compared to Roundup®, this time in large plot experiment.

[0064] A weedy field was divided into four 100 m.sup.2 plots, designated “Site 1”, “Site 2” and “Site 3”. Each field was treated with a different type of herbicide:

[0065] Site 1: Roundup®; 2 L diluted with 100 L of water.

[0066] Site 2: Roundup®+NaOH/KOH/Ca(OH).sub.2; 2 L of commercial product+500 g NaOH/KOH/Ca(OH).sub.2 (5:3:2) diluted with 100 L of water.

[0067] Site 3: NaOH/KOH/Ca(OH).sub.2; (10 g in liter water, 5:3:2).

[0068] The herbicidal compositions were sprayed at rate of application of 10 liter per 100m.sup.2. Soil samples were collected before the treatment started (t=0 days) and after 14 days (t=14 days) to measure various soil parameters as tabulated below in Table 2.

[0069] The results of the large plot experiment (each plot having a size of 100 m.sup.2) were consistent with the results reported in the smaller scale experiment (where each plot had a size 1 m.sup.2) of Example 4. That is, the most efficient treatment was observed in Site 3, showing an accelerated effect compared to Roundup®.

TABLE-US-00002 TABLE 2 SITE 1 SITE 2 SITE 3 t = 0 days t = 14 days t = 0 days t = 14 days t = 0 days t = 14 days PH 5.74 5.92 6.4 6.78 6.24 6.59 K cmol/LS 0.37 0.32 1.04 1.22 0.66 0.65 Na cmol/LS 0.33 0.38 0.36 0.55 0.26 0.71 Ca cmol/LS 6.28 5.87 6.16 6.18 6.38 5.87 TOC mg/kg 2.33 2.27 2.23 2.57 2.50 2.47 Organic 4.01 3.91 3.83 4.39 4.29 4.25 material mg/kg Moisture % 23.85 22.35 23.9 23.8 24.5 22.8