DD252748A1 - INFLUENCE OF HERBICIDE PERSISTENCE - Google Patents

Abstract

The invention relates to influencing the persistence of soil herbicides by application of urea before, after and together with the herbicide application. The combination of urea with herbicides causes a different persistence increase and thus prolonged effect, which is particularly pronounced in herbicides with urea structure. Targeted persistence management leads to economically favorable effects in certain areas of the economy.

Description

Field of application of the invention

The invention relates to the use of urea for influencing, in particular increasing, the persistence of herbicides, especially those with urea and amide structure.

Characteristic of the known technical solutions

Herbicides are subject to a more or less rapid degradation after their application in the soil. This can be physical, chemical and / or microbial. Speed and type of degradation depend on many factors. First and foremost, the chemical constitution of the drug is crucial. But also the conditioning and formulation necessary for the conversion of the active substance into an application-capable form influence the degradation in the soil. The concentration dependence also plays a role, but in general only at considerable concentration fluctuations. For example, unsubstituted aniline in the low concentrations in which it occurs as a metabolite after normal application rates of some carbamate and urea herbicides degrades extremely rapidly in the soil (SPENGLER, D., and JUMAR, A .: Arch. Pflanzenschutz 5 [1969], 6.445 to 453); on the other hand, when larger amounts of aniline are produced, microbial degradation is inhibited, presumably because aniline acts as a microbial and enzyme toxin (RABSCH, W .: Dissertation Universität Halle, 1976).

Of far-reaching importance for the fate of a herbicide-type xenobiotic, however, is soil texture. So z. B. the chemical-hydrolytic degradation of the pH, the water content and the content of the soil of catalytically active alumina minerals and zeolites influenced. This also applies to oxidative and reductive processes, in which, however, biochemical reactions that are often preceded by microbial reactions and dependencies on aerobic and anaerobic conditions are observed. The sorption properties of the soil also have significance for the degradability insofar as adsorptive fixation of the active ingredient can mean that the active substance is not only no longer available for the biological receptor, but is also removed from chemical and biochemical degradation. The humus content has the most important influence on the degradability of the chemical substance in the soil. Not only the chemical nature of the humus, its humic acid content, a role, but above all the content of microbes play a role. With their numerous strains and their adaptive capacity, they are of decisive importance for the degradation of a chemical in the soil.

While the above persistence-influencing factors provide starting points for artificial control, climatic factors such as temperature, wind, precipitation and UV radiation, which are naturally also important for drug degradation, are unlikely to be exploited under persistent field conditions , The persistence of a herbicidal active ingredient is directly related to its application effect, in that high persistence usually results in high sustained action, which is generally desirable and economically effective. On the other hand, a high persistence can also be disadvantageous, because, for example, crops of secondary crops are damaged or, more generally, the environment is undesirably polluted. To control the persistence of drugs and thus their availability in the soil, the formulation technique is often used. Thus, the incorporation of active ingredients in granules, which gradually disintegrate in the soil, or capsulation, which allows for gradual diffusion of the active ingredient through the enveloping membrane, result in prolonged release of the active substances. This slow-release technique can sometimes be achieved by other, physical or chemical fixation of the active substance to a polymeric matrix (HARTMANN, M., and KLEMM, D .: Mittbl. Chem. Ges. 33 [1986], 1,3 -8th).

Also known is the persistence influence by adding second and third active ingredients in combination preparations. The active ingredients can affect each other in their rate of degradation. For example, the half-life of the degradation of the beet herbicide Proximpham in the presence of the second component lenacil is almost doubled, apparently because the microbial degradation is inhibited (HAMROLL, B., and JUMAR, A .: Chem. Techn., 25 [1973], 7, 423-424). , When defenuron is combined with simazine, the degradation of defenuron by simazine is slowed in some soils (JUMAR, A., SIEBER, K., and LADEWIG, C: specifically, agrochemical psm A 2 [1978], 1,2-3). The interaction of different pesticides with respect to their biodegradation, also in the soil, was mainly studied by KAUFMANN, D.D. (Pestic. Chem., 6 [1972], 175-205, and 9 [1977], 49-57) and WALLHÖFER, P. et al. (Z. Pflaendh., Pf! Schutz, VIII [1977], 199-207). Soil persistence studies of herbicide mixtures of bromoxynil, propanil and dicamba have been described by SMITH, A.E. in Weed Res., 24 (1984) 4,291-295. HYZAK, D.L. has been found to protect N-methylcarbamoyloxyanilides as an extender of the efficacy of thiolcarbamate herbicides (US 4381195 [20.4.81 / 26.4.83]), with persistence prolongation certainly playing a role. The same effect in the EPTC additives of O-aryl-N-methyl-carbamates (US 4386955 [20.4.81 / 7.6.83]). In summary, the persistence of carbamate pesticides and their influence on soil by pesticidal secondary components as a consequence of

RAJAGOPAL, B.S., BRAH MAPROKASH, G.P., REDDY, B.R. et al., Have been found to affect soil microorganisms. Rev., 93 (1985), 1-199, especially 117-118 and 153. However, it must not be overlooked that the introduction of additional active substances into the soil poses ecotoxicological problems.

In order to influence the effects of herbicides, fertilizers that are ecologically insignificant must therefore be tried on a trial basis. Urea also played a role here, in combination with Phenmedipham and Lenacil (BACH, H., STÖCKEL, C. et al., DD 160 555 of 20.5.81) and asulam (CATCHPOLE, AH et al., GB 32705- 76 v. 5.8.76). However, the use of these agents as foliar herbicides in conjunction with urea excludes a persistence extension, as it deliberately intends to improve leaf penetration and transportability immediately after application. According to MARSH, J.A.P. (Pestic. Sci., 16 [1985], 93-100), the rate of degradation of dalapone and isoproturon in NPK-fertilized soil was reduced. Most studies relate to the influence of degradation and residue formation of pesticides in the presence of natural organic fertilizer and inorganic fertilizers, i.a. the N fertilizers ammonium sulfate and ammonium nitrate. An important role is played here by the insecticides parathion and DDT (FERRIS, LG., And LICHTENSTEIN, EP: J. Agric. Food Chem., 28 [1980], 1011-1019; see also FLASHINSKI, SJ, and LICHTENSTEIN, EP: Can. J. Microbiol., 21 [1975], 17) as well as carbaryl, whose stability in irrigated cultures and in nitrogen deficiency is increased by ammonium sulfate and urea, but not by potassium sulfate (RAJAGOPAL, BS, and SETHUNATHAN, N .: Pestic , 15 [1984], 6, 591-599). Of the fungicides studied, captafol and benomyl are in the foreground (LICHTENSTEIN, E.P. et al .: J. Agr. Food Chem., 28 [198O], 1011-1019 and 30 [1982], 871-878). In the soil herbicides linuron and monolinuron (GALIULIU, RV, SOKOLOV, MS, SUCHOPAROVA, VP et al .: Agrochimiya [Moscow] 1979, 6, 109-116), propachlor, desmetryn, aziprotryn (SIRKO, TS, and BELOVA, VI: Chim. selskom. choz. [Moscow] 1982,1, 51-53) as well as terbutylazine and toluin (CHUBUTIJA, RJ et al .: Agrochimija [Moscow] 1980, 2, 31-134; see also 1980, 5, 124-127) became influences on active substance intake by the plant, residue, effect and phytotoxicity with natural manure, K and NPK fertilizer examined.

Object of the invention

The aim of the invention is to improve the influence of the active ingredient persistence, the economy of the herbicide use and to limit the resulting from a multiple use of herbicides soil and plant stress. In addition, the non-rational and unproductive multi-application herbicides in the nonselective sector, which are often characterized by significant disruption to the economy, e.g. As the transport, accompanied, are reduced.

Explanation of the essence of the invention

Surprisingly, it has been found that the combined use of urea and herbicides applied to the soil can not - as expected - lead to the faster microwave degradation, but on the contrary to a delayed degradation and thus to an increase in persistence. Whether the addition of urea exerts an influence on the rate of degradation and whether in particular it inhibits the degradation and thus leads to an extension of the activity of the herbicide depends primarily on the chemical structure type of the herbicide. In addition, there appears to be a dependency on the length of the lag phase of the herbicide, ie the degradation delay phase, which is considered to be typical of microwave degradation and usually as Adaptationszei't the soil bacteria for the utilization of the active ingredients as carbon and / or energy source is interpreted. Herbicides, which in any case have a short decomposition time, do not seem to be affected, or are only slightly influenced, by their microbial degradation, and those with a long degradation time experience a clear prolongation of their persistence. Thus, in corresponding experiments, a-halocarboxylic acid herbicides, such as TCA, have a relatively low degradation delay by urea, as do carbanilate herbicides, eg. B. Propham, Chlorpropham, Proximpham (Tab. 6)

 Herbicidal chloral derivatives were unaffected. On the other hand, representatives of the acetanilide herbicides, but especially the aryl urea and uracil herbicides, showed an unexpectedly marked increase in persistence in the presence of urea. It has become clear that herbicides with the structural feature of urea or thioureas in the molecule, ie arylureas, arylmethoxyureas, hetarylureas, arylthioureas and uracil derivatives in interaction with urea greatly increase their persistence and thus their duration of action (Table 4 and 5).

Whether and to what extent a group of herbicides responds to the addition of urea can only be determined empirically in the absence of theoretical principles. In the experiments carried out, the half-lives of the degradation of the mostly radiolabeled herbicidal active compounds in different soil types with and without urea were determined and compared in an exact manner (see Tables 1-3). The results substantiate and explain the results obtained in biological experiments to increase the duration of action of herbicides under the influence of urea. Given the variety of processes and interactions between xenobiotics, urea, soil constituents and microbes in the soil, the end effects are not easily predictable. A role is played by the fertilization of the soil by urea and the associated influence on microbial activity; the competition of excess urea with xenobiotics as a source of nutrients for soil microbes; the influence of the adaptive capacity of the soil microbes and thus of the lag phase; the solubility properties of the urea and its ability to adhere to mineral constituents of the soil, which can lead to a displacement of adsorbed active agent molecules from the adsorption centers or catalytic centers of the soil; to block the ammonification capacity of the urea and the property of the resulting ammonium ions to catalytically active hydrolysis centers; the different solubility of the active substances and thus different migration behavior in the soil, which leads to the separation of the urea molecules and thus to differentiated interactions between urea, active ingredient and soil particles; u.a.m

 The object of Persistenzbeeinfiussung of soil herbicides is thus inventively achieved in that the herbicidal active ingredient, formulated as a ready-to-use preparation and prepared as a spray mixture, in the prescribed for weed control hectare amount, combined with urea, is applied. In this case, the urea can be added to the aqueous spray mixture, but also be applied to the soil before or after the herbicide application. Because the

Urea fertilization is one of the common agricultural-chemical measures, can also combine herbicide application and nitrogen fertilization in this way. It is also possible to process urea and herbicidal active ingredients to combined solid, liquid or flowable preparations, excipients, fillers, solvents, surfactants u. a. Formulation aids are used and the herbicides usual formulation technology is used. The formulation processing to solid preparations, such as wettable powders, is contrary to that urea with some chemical compounds, including herbicidal active ingredients, molecular compounds received; These adducts sometimes have better formulation properties than the mere active ingredients because of increased melting points. The urea is used in considerable molar excess relative to the herbicidal active ingredient. The application rates per hectare are therefore up to 500 kg urea, preferably 40 to 400 kg urea.

Targeted control of persistence soil soil herbicides in soil is of considerable interest to users of crop protection measures in agricultural practice. Thus, by prolonging the persistence, the spectrum of action of such herbicides, which must be used already at the beginning of the growing season, be extended to the later germinating weed species. In permanent crops, esp. In forestry, by using the effect of prolonged herbicides, the manual and mechanical care effort is significantly reduced. In addition, the use also results in the nonselective range, where long-lasting foliar killing agents, e.g. on paths, squares, industrial facilities, track and pavement routes are in demand, to an increase in efficiency and improved economy. The elimination or reduction of multiple treatments further limits disabilities, impediments or disabilities in the economy, especially in the transport sector. Overall, the control of herbicide persistence is therefore of great importance for the completion of a weed control adapted to the different circumstances and requirements.

embodiments

The following examples and tables are intended to illustrate the invention without limiting it.

example 1

Determination of the soil persistence of Fenuron (N-phenyl-N ', N'-dimethylurea) In 6 300 ml Erlenmeyer flasks per test series, 50g of sieved clay soil with water were added to 30% of maximum water capacity (MWK = 46g H ₂ O) / 100g soil) and incubated at 18 ° C for 24 hours. Subsequently, ¹⁴ C-fenuron was applied at a rate of 1.4 mg / 50 g soil (Ä28.4 ppm), or 1.4 mg ¹⁴ C-fenuron + 228 mg urea / 50 g soil (= & 200 kg N / ha). The "bottom surface" in the flask was 5.7 x 10 ^"7 ha. The application of the radioactive drug was carried out in aqueous-ethanolic solution of urea in aqueous solution, with the amounts of water that therefore the soil humidity adjusted to 40% MVC was. The solution, which was distributed dropwise on the floor using a pipette, was evenly distributed in the bottom by shaking it in the flask for 3 minutes. Until sampling, the flasks sealed with cotton plugs were then stored in the dark at 18 ° C. in the incubator. For work-up, the contents of each flask were mixed with 10 ml of methanol and extracted on the shaker for 30 min. Thereafter, the soil and extract were separated by suction using a suction filter and a water jet pump. Removal of 3 ml of the extract and measurement in the spectrometer (tricarb) after the addition of 10 ml of toluene scintillator in each case determined the radioactivity. The assignment, whether it is unchanged drug or transformation products (TP), was carried out by thin layer chromatography in comparison to the authentic sample.

Time after application Determined percentages of discontinued ¹⁴ C-fenuron radioactivity in% fenuron adherent ¹⁴ C balance fenuron extractable 97.5 Fenuron + TP 87.8 2.4 99.9 3Stdn. 97.5 72.1 13.0 100.8 7 days 87.8 54.0 25.1 100.3 17 days 75.2 47.9 39.0 99.7 31 days 60.7 44.3 100.5. 45 days 56.2 100.4 Fenuron + urea 97.1 - 100.4 3Stdn. 100.4 84.2 3.4 100.5 7 days 97.1 72.5 16.7 100.9 17 days 84.2 70.9 25.6 101.4 31 days 75.8 26.0 100.1 45 days 74.1

By regression analysis, the measured points (mean values from two series of measurements) were fitted with a regression equation which followed a first-order reaction (y =% Fenuron, χ = time in days). The correlation coefficient r describing the goodness of fit was determined. From the regression equation the half life T _{1/2 was} calculated; di the number of days (x) after which the active ingredient is 50% degraded (y = 50).

fenuron X = 0.125 7 17 31 45 In y = 4.5716-0.016647 x YEXP. 97.5 87.8 72.1 54.0 47.9 r = 0.990 T _1/2 = 40days Yber. 96.5 86.1 72.9 57.7 45.7 fenuron + Urea In y = 4.6041 - 0.0085626 x YEXP. ioo; 4 97.1 84.2 72.5 70.9 r = 0.968 Ti / 2 = 81 days Yber. 99.8 94.1 86.4 76.6 68.0

As can be seen from the comparison of the half-lives T _1/2 , the persistence of fenurone by urea is extended to double.

Example 2

Determination of Soil Persistence of Bromuron (N-4-Bromophenyl-N ', N'-dimethylurea) Following the experimental setup and methodology described in Example 1, the persistence of bromuron alone and of bromuron in the presence of urea was determined. The application rates were 1.15 mg ¹⁴ C-bromuron / 50 g soil (in the form of a 50% spray powder) and 228 mg urea / 50 g soil. The examination duration was 120 days. From the regression equations adapted to the experimental findings, the half-life for bromuron at Ty ₂ = 88 days and for bromuron + urea at Jy ₂ = 293 days was determined, which corresponds to a more than 2.5-fold extension.

Example 3

Determination of soil persistence of Lenacil P-cyclohexyl-S 1-trimethyleneuracil) The half-life determination was carried out according to the methodology described in Example 1 using a DC scanner to identify and determine the activity. The application rates were 1.14 mg ¹⁴ C-lenacil / 50 g soil and 228 mg urea / 50 g soil. The investigation period was 260 days. Persistence was studied in two soil types with the following characteristics:

Soil Water capacity [%] Org.C humus T-value [mval] pH value (KCl) volume silt sand Light ground Heavy ground 26 35 0.6 1.6 1,1 2,8 4,4 20,6 6.4 6.1 7 19 18 74 From left to right

The graphically determined half-lives are given in Table 1. Thereafter, the half-life (Ti _{/ 2} ) of lenacil degradation in the soil by urea is extended by 1.3 to 2.3 times.

Table 1

Lenacil degradation with and with urea in light and heavy soil j

T _1/2 (in days) T ₁ Z ₂ on days)!

in light soil in heavy soil j

Lenacil 440 97

Lenacil + urea 566 227

Example 4 j

Determination of soil persistence of TCA (trichloroacetic acid) |

It was worked with the sodium salt ¹⁴ C-TCA-Na analogously to Example 1 and with the characterized in Example 3 soils. !

Application rates: 9.1 mgTCA / 50g soil and 228 mg urea / 50g soil. The determined half-lives (T _1/2 ) can be found in | Tab. 2. The increase in persistence amounts to 1.3 times.

Table 2

TCA degradation with and without urea in light and heavy soil I

'j

T _{1/2 1/2} (days) j (in days) T

in light soil in heavy soil i

TCA + urea 45 32

Example 5

Determination of soil persistence of DCU (dichloralurea)

The application rates were 11.4 mg ¹⁴ C-DCU / 50 g soil and 228 mg urea / 50 g soil. The extraction of the soil was carried out with acetone. The half-life of light soil degradation was T _1/2 = 9 days, in heavy soil T _1/2 = 6 days. With added urea, the half-lives remained nearly unchanged in accordance with theoretical considerations. In the case of DCU, the urea acts merely as a "chemical carrier" for the actual herbicidal agent, the chloral In the soil, dichloralurea decomposes rapidly via monochloralurea to urea and chloral or its derivative chloral hydrate.

Examples

Determination of the soil persistence of propachlor (2-chloro-N-isopropyl-acetanilide) In two different soil types 9,12 mg ¹⁴ C-propachlor / 50 g soil (as spray powder) and 228 mg urea / 50 g soil were used analogously to Examples 1 and 3. In addition to the radiochemical method, the soil extraction values were also determined by gas chromatography with inactive propachlor. The determined half-lives (T1 / 2) are listed in Table 3. The proliferation of persistence amounts to approximately 1.6 times independent of soil type.

Table 3

Propachlor degradation without and with urea in light and heavy soil

T ₁₇₂ (in days) in light soil

T _1/2 (in days)

in heavy ground

Propachlor Propachlor + Urea

18 28

11 18

Example 7

The effects of persistence change under practical conditions of use are proved as follows:

The application of the herbicide with and without addition of urea and at a later time the sowing of lettuce, in order to detect the influence of urea on the persistence of the herbicide. The influence on crop development by the variants was recorded in the form of assessments. Where:

1 = no influence on the test plant

9 = plants totally destroyed.

In a field trial, the application of lenacil in a 80% WP formulation was carried out in three different application rates, each with and without urea. The application rates per unit area corresponded to the conditions in agricultural practice. The application was carried out uniformly on the same day on 5 plots each for each application rate as well as for the lenacil variants with urea addition.

At intervals of 8,12,14,16 and 18 weeks after the application, the sowing of lettuce was carried out to determine to what extent differences in the duration of action between the sole application and the application of the herbicide with urea are given. The example (Table 4) shows that the addition of urea prolongs the persistence of the lenacil.

Table 4

Influence on the persistence of lenacil by adding urea under practical conditions to 5 different dates

Ser. No. probe member Weeks after the application 12 14 16 18 8th 1.5 1.0 1.6 1.3 1 untreated 1.5 6.8 3.2 3.3 3.2 2 Lenacil 1.76 kg / ha 7.2 3 Lenacil 1.76 kg / ha + 8.0 5.2 6.7 6.2 Urea 200 kg / ha 8.3 6.3 2.3 2.3 2.0 4 Lenacil 1.28 kg / ha 6.3 5 Lenacil 1.28 kg / ha + 7.0 4.4 3.9 2.5 Urea 200 kg / ha 7.2 4.3 2.2 2.9 1.3 6 Lenacil 0.8 kg / ha 5.4 7 Lenacil 0.8 kg / ha + 5.5 2.2 3.0 2.0 Urea 200 kg / ha 6.4

Example 8

In a model experiment under greenhouse conditions, the application of four different herbicides with urea structure as WP formulations was carried out in practical application rates each without and with addition of urea. Salads were sown in the treated soil 12 weeks after application to determine the differences in persistence between use alone and the use of urea herbicides (Table 5). The example proves that there is an influence on the persistence by urea addition.

Table 5.

Influence on the persistence of urea-modified herbicides by adding urea under model conditions 12 weeks after application.

Ser. No. herbicidal test element without urea 40 kg / ha urea 400 kg / ha urea 1 without herbicide 1 1 1 CS! Fenuron, 0.5 kg / ha 1 2 6 3 Fenuron, 1.0 kg / ha 1 CSI 6 4 Monuron, 0.5 kg / ha 1 1 4 5 Monuron, 1.0 kg / ha 2 5 6 6 Methabenzothiazuron, 2.0 kg / ha. 1 CSI 6 7 Metobromuron, 2.0 kg / ha 5 6 6 8th Fenthiuron, 1.0 kg / ha 1 CSI 4

Fenuron = N-phenyl-N ', N'-dimethylurea

Fenthiuron = N-phenyl-N ', N'-dimethylthiourea

Monuron = N- (4-chlorophenyl) -N ', N'-dimethylurea

Metobromuron = N- (4-bromophenyl) -N'-methoxy-N'-methylurea

Methabenzothiazuron = N- (2-benzthiazolyl) -N, N'-dimethylurea

Example 9

In a model experiment under greenhouse conditions, the application of 3 carbanilate herbicides as WP formulations was carried out uniformly on the same day at practical application rates without and with the addition of urea. 12 weeks after application, lettuce was sown in the treated soil to determine the differences in persistence between use alone and the use of urea herbicides (Table 6). The example demonstrates that the addition of urea hardly influences the persistence of the herbicides.

Table 6

Influencing the persistence of carbanilate herbicides by adding urea under model conditions 12 weeks after the application

Ser. No. herbicidal test element without urea 40 kg / ha urea 400 kg / ha urea

1 without herbicide 1,1 1

2 chlorpropham, 2.5 kg / ha 1 1 2

3 Propham, 2.5 kg / ha 1 1 2

4 proximpham, 2.5 kg / ha 1 1 1

Claims (3)

1. Influence of herbicide persistence in the soil, characterized in that in combination with the herbicidal application, an additional application of urea takes place. 2. Influence on the herbicide persistence according to item 1, characterized in that to increase the persistence of herbicides with urea and amide structure, their application is combined with urea. 3. Influence of the herbicide persistence according to item 1, characterized in that the urea in application rates up to 500 kg per hectare, preferably from 40 to 400 kg per hectare, is applied.