Topramezone: A selective post-emergence herbicide in chickpea for higher weed control efficiency and crop productivity

Highlights

• We studied selectivity of POST herbicides and topramezone was selective in chickpea.

• Topramezone 20.6 g a.i. ha⁻¹ effectively controlled dominant broad-leaved weeds.

• It had higher WCE (76.5-89.8%) and WCI (75.1-93.2%) than other treatments.

• It increased 15.3-19.6% chickpea yield than pendimethalin - quizalofop-p-ethyl.

• Topramezone increased microbial biomass C than pendimethalin - quizalofop-p-ethyl.

Abstract

Chickpea (Cicer arietinum L.) is a dominant pulse crop in the world for its climate resilience and nutritional values. Weed infestation causes a significant yield loss in chickpea and jeopardize in realizing the potential yield across regions. Pendimethalin as pre-emergence (PRE) is the ruling herbicide, however, post-emergence (POST) herbicides are limited in this crop particularly for managing broad-leaved weeds and higher yield gain. We assessed the impact of POST herbicides available in different crops on weed phytotoxicity, crop selectivity and yield performance in chickpea on sandy-loam soil of Kanpur, India. The experiment was undertaken for two consecutive years (2016-17 and 2017-18) comprising nine herbicides, besides unweeded control (UWC) and weed-free check (WFC). Among the herbicides tested, halosulfuron-methyl 70 g a.i. ha⁻¹ and tembotrione 100 g a.i. ha⁻¹ showed the maximum phytotoxicity scale of 5-10 on chickpea. Clodinafop-propargyl + sodium-acifluorfen 122.5 g a.i. ha⁻¹ and imazethapyr + imazamox 70 g a.i. ha⁻¹ had a recoverable phytotoxicity (scale 3–5) on chickpea. Topramezone 20.6 g a.i. ha⁻¹ at 25 days after sowing (DAS) resulted in higher phytotoxicity on weeds (toxicity scale of 7–10) without any phytotoxicity on chickpea. It significantly controlled the dominant broad-leaved weeds: Chenopodium album L., Lepidium didymum L., Spergula arvensis L., Medicago polymorpha L. and Fumaria parviflora Lam. compared to the remaining herbicides. Topramezone reduced total weed density by 68-70% and 48–51% (P ≤ 0.05) at 45 and 95 DAS compared with UWC, respectively. Therefore, this herbicide had higher (P ≤ 0.05) weed control efficiency in both years (89.8% in 2016-17 and 76.5% in 2017-18) than remaining treatments. Topramezone increased 15.3-19.6% chickpea seed yield than the recommended herbicide pendimethalin 1000 g a.i. ha⁻¹ - quizalofop-p-ethyl 100 g a.i. ha⁻¹ without affecting the nodulation and fluorescein diacetate activity. The UWC resulted in 64% (mean of two years) yield loss compared to the WFC in chickpea. Importantly, topramezone gave comparable yield with WFC. Hence, topramezone can be safely used in chickpea for managing broad-leaved weeds and realizing higher productivity.

Introduction

Chickpea (Cicer arietinum L.) is one of the important pulse crops in the world covering 14.6 M ha area with 14.8 Mt of production (Merga and Haji, 2019). In India, chickpea is grown on an area of 10.6 M ha with a production of 11.2 Mt (Nath et al., 2018). Chickpea is valued for its nutritional quality in the vegetarian diet as it is an important source of proteins and minerals (Nair et al., 2014). Also, pulse crops are promoted in cropping system intensification and diversification to ensure the sustainable productivity and prevent soil degradation (Ghosh et al., 2016). Specifically, chickpea plays an important role in conservation agriculture systems because of resource saving and biological N₂ fixation (Nyanga, 2012). However, the yield of chickpea has remained stagnant over the last few decades in spite of its higher yield potential (Nair et al., 2014). Therefore, research on chickpea will have a significant impact on sustainable cropping intensification, soil fertility and nutritional security.

Severe weed infestation is one of the important limiting factors of higher yield in chickpea (Nath et al., 2018). In fact, chickpea is a poor competitor to weeds because of its slow initial growth and vegetative cover, resulting in yield loss up to 80% under season long weed infestation. On an average, yield reduction of 24-63% has been reported in chickpea (Muhammad et al., 2011). Presently, pre-emergence (PRE) application of pendimethalin 1000 g a.i. ha⁻¹ followed by hand weeding is advocated for weed management in chickpea (Kumar et al., 2015). However, hand weeding is a cumbersome process because of limited availability of labour at critical period and increasing cost. Also, application of pendimethalin as PRE does not control the later flush of weeds after one month of sowing (Singh et al., 2014). Therefore, post-emergence (POST) herbicides are essential but there is no such herbicide recommended especially for controlling broad-leaved species. Some studies have suggested the application of imazethapyr in chickpea (Kachhadiya et al., 2009; Khope et al., 2011), but lower weed control efficiency and phytotoxicity to crop hinder its wider adoption (Kumar et al., 2016). Quizalofop-p-ethyl 100 g a.i. ha⁻¹ (Kumar et al., 2015) and fenoxaprop-p-ethyl 100 g a.i. ha⁻¹ (Ansar et al., 2010) are recommended in chickpea to control grass weeds, but the dominant broad-leaved weeds such as Medicago polymorpha L., Vicia sativa L., Convolvulus arvensis L., Chenopodium album L., Melilotus indicus (L.) All. and Rumex dentatus L. cause severe yield loss in chickpea (Nath et al., 2018). Thus, there is an urgent need to investigate the selectivity of different POST herbicides for their broad-spectrum activities in chickpea to minimize the yield loss and higher weed control efficiency.

Few POST herbicides such as topramezone and tembotrione in maize (Zea mays L.) (Arslan et al., 2016), clodinafop-propargyl + sodium-acifluorfen in soybean (Glycine max (L.) Merr.) (Jha et al., 2014) and oxyfluorfen in sunflower (Helianthus annuus L.) (Jursik et al., 2011) are recommended, but their efficacy and selectivity in chickpea are not well established. Topramezone [3-(4,5-Dihydro-3-isoxazolyl)-2-methyl-4-(methylsulfonyl)phenyl](5-hydroxy-1-methyl-1H- yrazol-4-yl) methanone] inhibits the hydroxylphenyl pyruvate dioxygenase enzyme of carotenoid biosynthesis (pigment). It is selective to maize by rapidly metabolizing the herbicide into non-active substances and used primarily to manage broad- and narrow-leaved weeds (Arslan et al., 2016). Tembotrione, carfentrazone-ethyl and sodium-acifluorfen belong to the pigment synthesis inhibiting herbicides causing chlorosis and bleaching action on plants (Das, 2008). These herbicides play an important role in formation of singlet/reactive oxygen which damage the carotenoids and cause death of plant cells (Dekker and Duke, 1995). Imazethapyr + imazamox and halosulfuron-methyl inhibit the acetolactate synthase and acetohydroxy acid synthase enzymes and check the synthesis of branched chain amino acids that include leucine, isoleucine and valine (Ashton and Crafts, 1973). Quizalofop-p-ethyl and fenoxaprop-p-ethyl are aryloxyphenoxypropionate group herbicides with acetyl Co-enzyme A carboxylase inhibiting activities (Cocker et al., 1999; Lucini and Molinari, 2011). These informations are useful for the assessment of target site of action, selectivity, bio-efficacy of herbicides and guiding the rational use of herbicides in agriculture.

In fact, the selectivity of herbicides are dose, time, stage and crop dependant (Das, 2008), hence, herbicide selectivity can be manipulated (Susha et al., 2018). Therefore, the present investigation was undertaken to assess the crop selectivity, weed phytotoxicity and seed yield of chickpea under different POST herbicides. We hypothesized that amongst the available POST herbicides in different crops few may be selective to chickpea without crop phytotoxicity and give higher weed control efficiency and seed yield.