كاهش اثر منفي حامل آب‏ سخت بر كارايي توفوردي+ ام سي پي آ‏ به وسيله سولفات آمونيوم

Reducing the 2, 4 D+MCPA Antagonism from Hard Spray Waters by Ammonium Sulfate

تأثیر كاربرد ماده افزودنی به‏منظور مدیریت اثر حامل آب سخت بر علف‏كش توفوردی+ ام سی پی آ در بهار و تابستان 1392 در یك زمین چمن مخلوط 10 ساله اقلیم سرد آلوده به شبدر سفید (Trifolium repens L.) در مشهد در یك آزمایش فاكتوریل در قالب طرح بلوك‏های كامل تصادفی در سه تكرار بررسی شد. فاكتور اول شامل سختی‏های صفر (آب نرم)، 45، 90 و 180 ppm (Ca 2+ +Mg2+ ) و فاكتور دوم مقادیر صفر، دو، سه، و چهار درصد سولفات آمونیوم در آب حامل علف‏كش بود. تراكم و وزن خشك شبدر و چمن اندازه‏گیری شد. تمام سطوح سختی آب سبب كاهش كارایی علف‏كش روی شبدر شد. سولفات آمونیوم به تنهایی تأثیری بر سمیت آن نداشت بلكه در مواجهه با سختی نقش ضد آنتاگونیستی خود را ایفا نمود و اثر آنتاگونیستی كاتیون‏ها را خنثی كرد. در سختی 45 ppm افزایش میزان سولفات آمونیوم در آب حامل علف‏كش تا چهار درصد به بازیابی سمیت علف‏كش كمك كرد ولی در سختی‏های 90 و 180 ppm افزایش بیش از دو درصد سولفات آمونیوم به آب حامل علف‏كش سودی در پی نداشت. علف‏كش روی چمن گیاه‌سوزی ایجاد نكرد بلكه با افزایش سولفات آمونیوم در آب نرم، چمن از آن به عنوان یك منبع غذایی بهره برد و وزن خشك آن افزایش یافت. افزایش میزان سختی تأثیری بر وزن خشك چمن نداشت و برتری عملكرد تیمار آب نرم ناشی از كنترل بهتر شبدر و تأثیر غیر مستقیم روی چمن بود.

Introduction: Water is the main carrier of herbicides (HC) that its quality plays an important role in herbicide performance hard water has a high concentration of Ca++ and Mg++ and reviews have shown that calcium, manganese and zinc are the main factors reducing the effectiveness of weak acid herbicides. Weak acid herbicides such as glyphosate, paraquat, clethodim and 2, 4 D are compounds that release the H+ ions once dissolved in water, but just slightly. Therefore, herbicides that are weak acids partially dissociate. Herbicides not dissociated (the compound remains whole) are more readily absorbed by plant foliage than those that dissociate. Dissociated herbicide molecules have a negative charge. After being dissociated, herbicides might remain as negatively charged molecules, or they might bind with other positively charged cations. Binding to some cations improves herbicide uptake and absorption, binding to others such as Ca++ and Mg++ antagonizes herbicide activity by decreasing absorption or activity in the cell. To correct such carriers, the use of adjuvants, such as ammonium sulphate (AMS), is recommended, which can reduce the use of herbicides and cause economic savings. The aim of this study was to investigate the simple effects and interactions between different amounts of AMS and carrier hardness (CH) levels on 2, 4 D + MCPA herbicide efficacy in controlling white clover (Trifolium repens L.) in turf grass. Materials and Methods: The experiment was laid out in a RCBD with three replications for each treatment during spring-summer 2013 in 10 years old mixed cold season turf grass (Festuca rubra + Poa pratensis + Poa pratensis) dominated by white clover in Mashhad (Iran). The treatments were the factorial combination of four carrier hardness (CH) rates (Deionized, 45, 90 and 180 ppm of Ca++ +Mg++) and three Ammonium Sulfate (AMS) rates (0, 2, 3 and 4 Kg per100 L of carrier water) were studied. The turf was sprayed with 2, 4 D + MCPA (67.5% SL) at 1.5 L-ha applied once on July. The density and dry matter of clover and turf were recorded. Results and Discussion: Full performance of 2, 4 D + MCPA herbicide to control clover, regardless of the amount of ammonium sulfate used, was obtained in soft water. Adding just 4%, AMS to Carrier water with a hardness of 45 ppm could recover effectiveness of herbicide up to DI water, whereas in 90 ppm of hardness adding only 2 percent ammonium sulfate was enough to increase herbicide efficacy to twice as no ammonium sulfate treatment. The most significant antagonism effect was obtained in 180 ppm hardness level without AMS reducing 84% of 2, 4 D + MCPA performance compared to soft water. The highest antagonism effect of the herbicide carrier went to 180 ppm, 90 ppm and 45 ppm of hardness respectively. Overall, the study revealed that only in 45 ppm of CH the addition of 4% of AMS will help to restore the toxicity of 2, 4 D + MCPA while in 90 ppm and 180 ppm of CH add more than 2% of AMS to 2, 4 D + MCPA carrier water will not benefit the herbicide toxicity. Most reports have considered sufficient two percent of AMS to neutralize the inhibitory effect of CH on the weak acid herbicides. Three weeks after spraying, no phytotoxicity was found in the grass. At the same time interaction between CH and AMS on the lawn dry weight was significant (P <0.01). Accordingly, the ammonium sulfate levels rose in all levels of CH grass dry matter increased. This result suggests the use of AMS as a food source by grass. Conclusion: Increasing AMS level in carrier water had no effect on herbicide toxicity performance alone but plying its role in presence of hardness by reducing the antagonistic effect of hardness. Only in 45 ppm level of carrier hardness The CH antagonism on 2, 4 D + MCPA toxicity can be reduced AMS level up to 4% can reduced. Increasing AMS level more than 2% did not significantly antiantagonied 90 and 180 ppm of hardness. No injury was observed by 2, 4 D+MCPA on turf while AMS benefited for turf because of its nitrogen content. Increasing CH had no significant effect on turf dry mater and deionized performance advantage was due to indirect influence of better control of clover.