Response of IWM Strategies on Growth, Nodulation, Productivity and Profitability in Fenugreek (Trigonella foenum-graecum L.) under Haryana Conditions

Legume is recognized as the most beneficial plant because of having high grain protein contents and ability to fix biological nitrogen. The genus Trigonella is one of the largest genera of the tribe Trifoliate in the family Fabaceae and sub-family Papilionaceae (Balodi and Rao, 1991). Fenugreek (Trigonella foenum-graecum L.) prevalently known as its vernacular name “Methi” is an important condiment crop grown in northern India during rabi season. Fenugreek, a grain legume crop, occupying 169 thousand ha area with an annual output of 252 thousand MT and average productivity of 1.7 MT ha^-1 (Anonymous, 2021). It is considered to be one of the important pulse crops having a rich source of protein (23 to 24%), macro and micronutrients (Ca, P, K, Fe and Zn), vitamins (niacin, vitamin A, ascorbic acid and inositol), fiber, carbohydrate. (Semwal et al., 2023).
       
Crop types and soil properties have greatest influence on the occurrence of weed species in a particular crop (Lugowska et al., 2016). Some pre-emergence (PRE) and post-emergence (POE) herbicides efficacy have been evaluated against weed flora in legumes. Imazethapyr applied as PPI, PRE and POE controls monocot and dicot weeds and had a strong residual life (Punia et al., 2011). Herbicides applied pre-emergence (PRE) or early post-emergence (POE) may not always provide season long weed control necessitating the use of integrated techniques for effective control. Therefore, a better and more suitable weed control method is needed for season long effective control of weeds in fenugreek with no adverse effect on succeeding sensitive crops. Keeping these points in view, it was considered to carry out field experiment on the efficacy of imazethapyr applied alone and its ready mixture with pendimethalin or imazamox in fenugreek crop. A recent decline in commodity prices and increasing herbicide costs to manage herbicide resistant HR weeds has spurred research efforts to build a strong rationale for developing ecologically based integrated weed management (IWM) strategies in the Indo-gangetic Plains. This article aims to document the role of IWM that will ultimately aid in achieving sustainable weed management goals and preserving the natural resources. Nutrients are very much essential for growth and development of fenugreek crop and their deficiency will decrease the crop yield. Therefore, it is imperative to know the uptake of nutrients by crop. Hence, the present study was undertaken with the aim to investigate the impacts of integrated weed management techniques on the growth, nodulation and nutrient uptake of fenugreek crop.

Field experiments were conducted during the winter season of 2018-19 and 2019-20 at Agronomy Research farm (29° 10'N, 75°46'E), CCS Haryana Agricultural University, Haryana. Fenugreek (Variety: HM-51) was sown on 22 November, 2018 and 19 November, 2019 during 2018-19 and 2019-20, respectively and the plot size was 6 by 6 m with a row spacing of 20 cm and seeding rate 25 kg per hectare. The soil at the experimental site was determined as sandy loam in texture, slightly alkaline in reaction (pH 7.8) and normal in electrical conductivity (0.28 dS m^-1). Field trials were set up with three replications in a randomised complete block design using six row m² plots with fifteen treatments. To ensure a homogenous plant population, excess plants were thinned out. The crop received 28.6 and 32.4 mm of rainfall in the crop growing season during both seasons, respectively. The soil of experimental field was sandy-loam at Hisar (58% sand, 32% silt and 10% clay). It was medium in organic carbon (0.51%), low in nitrogen (181 kg ha^-1), medium in phosphorus (17 kg ha^-1) and high in potassium (285 kg ha^-1) at experimental area. Fields were fertilised with 20 and 40 kg ha^-1 of nitrogen and phosphorous, respectively through DAP before sowing during both seasons. The experiment was conducted in a field heavily infested with broad-leaved weeds.
       
The herbicide treatments evaluated consisted of fifteen treatments in total. Weed free and weedy treatments were included for comparison of efficacy. Experimental treatments comprised weedy check, weed free, PRE imazethapyr at 80 g ha^-1, PRE imazethapyr + imazamox (RM) at 70 g ha^-1, PRE pendimethalin at 1000 g ha^-1, PRE pendimethalin + imazethapyr (RM) at 1000 g ha^-1, PRE pendimethalin + imazethapyr (RM) at 1250 g ha^-1, PRE pendimethalin + imazethapyr (RM) at 1500 g ha^-1, POE imazethapyr at 80 g ha^-1 at 3-4 leaf stage, POE imazethapyr + imazamox (RM) at 70 g ha^-1 at 3-4 leaf stage, PRE imazethapyr at 80 g ha^-1 + one hoeing at 3-4 leaf stage, PRE imazethapyr + imazamox (RM) at 70 g ha^-1 + one hoeing at 3-4 leaf stage, PRE pendimethalin at 1000 g ha^-1 + one hoeing at 3-4 leaf stage, PRE pendimethalin + imazethapyr (RM) at 1500 g ha^-1 + one hoeing at 3-4 leaf stage and two hoeing at 30 and 60 DAS. Plant protection measures and irrigations were followed as per recommendation. The pre-emergence herbicide was sprayed immediately after sowing on wet soil and post-emergence herbicides at 46 DAS as per treatment with knapsack sprayer.
       
Randomly five plants were selected from each plot and regular observations of crop and weed parameters were recorded from 30 DAS upto harvest. Nodule parameters viz. number and dry weight of nodules/plant were observed both at 40 and 60 DAS. Chlorophyll A and B content was recorded at 75 DAS (Kapoor et al., 2017). To estimate the N, P and K content, samples were collected at harvest for crop. Nutrient uptake by seed and haulm was calculated on the basis of dry matter yield with the nutrient content and expressed in kg ha^-1. Estimation of nitrogen was done by colorimetric method using Nessler’s reagent to develop colour. Phosphorus content was determined by Vanadomolybdo phosphate yellow colour method (Jackson, 1967) and potassium by Flame photometric method.
       
The data were subjected to analysis of variance and significant differences among treatments were tested. Differences among treatment means were determined using ANOVA and when the F-test was significant, means were compared with LSD test at 5% level of significance.

Broad-leaf weeds were present at comparatively higher densities and consisted mainly of Melilotus indica (7.7%), Anagallis arvensis (23.5%), Rumex dentatus (14.0%), Lathyrus aphaca (11.8%), Medicago denticulata (21.6%) and Coronopus didymus (7.7%) and among grassy weed Phalaris minor (13.7%) at 45 DAS.
       
Days taken to obtain 50% flowering (Table 1) were significantly higher under Pendimethalin at 1000 g ha^-1 PRE and imazethapyr at 80 g ha^-1 applied at 3-4 leaf stage as well as PRE and these were statistically at par with weedy check. The data revealed that Pendimethalin + imazethapyr (RM) at 1500 g ha^-1 + one hoeing at 3-4 leaf stage recorded minimum days to maturity excluding weed free treatment. Nodule parameters viz. number and dry weight of nodules/plant were observed both at 40 and 60 DAS (Table 1). All the weed-control measures had significantly positive impact on number and dry weight of nodules of fenugreek as compared to weedy check at all the growth stages. Number of nodules/plant were maximum under pendimethalin + imazethapyr (RM) at 1500 g ha^-1 + one hoeing at 3-4 leaf stage and it was statistically at par with PRE pendimethalin + imazethapyr (RM) applied at 1000, 1250 and 1500 g ha^-1. Pendimethalin + imazethapyr (RM) at 1500 g ha^-1 + one hoeing at 3-4 leaf stage application recorded significantly higher dry weight of nodules amongst all the chemical treatments which was at par with weed free treatment. In case of efficient weed control treatments, better weed management provided professed root development and bacterial colonies, which ultimately resulted in more nodulation in crop especially in herbicidal treatments with PRE Pendimethalin + imazethapyr (Dubey et al., 2018). Pendimethalin + imazethapyr (RM) at 1500 g ha^-1 + one hoeing at 3-4 leaf stage depicted higher nodular count owing to infestation of Rhizobium in the growing roots as compared to more crop weed competition in unweeded check (Nirala et al., 2016; Sharma et al., 2017). Amongst herbicide treated plots, both chlorophyll A and B were significantly higher in pendimethalin + imazethapyr (RM) at 1500 g ha^-1 + one hoeing at 3-4 leaf stage which was at par with imazethapyr + imazamox (RM) at 70 g ha^-1 + one hoeing at 3-4 leaf stage in case of chlorophyll A. The increase in chlorophyll content of the crop under weed control treatment with PRE Pendimethalin + imazethapyr at 1500 g ha^-1 can be clearly attributed to the reduction in interference of the weeds as evident from the higher weed control efficiency which ultimately favoured better growth environment for the crop (Sharma et al., 2017). Thus, under lesser crop weed competition, adequate availability of light, temperature and space along with moisture and nutrients, improved physiological and morphological characters of plant as well as photosynthesis with greater rate ultimately leads to more chlorophyll content in plants (Duncan, 1971).
 
                                 
 
Nutrient content in seed was recorded and significantly the lowest content of nitrogen, phosphorus and potassium by seed was noted under unweeded control (Fig 1) and maximum was observed under pendimethalin + imazethapyr (RM) at 1500 g ha^-1 + one hoeing at 3-4 leaf stage. Significant increase in total N, P and K content in haulm was recorded due to all weed management practices over weedy check (Fig 2). The highest nutrient content in haulm was recorded under weed free up to harvest. Similarly, all the weed control treatments significantly increased N, P and K uptake by seed and straw of fenugreek over weedy check (Table 2). Weed free treatment resulted in significantly highest total uptake of N (65.2 kg/ha), P (9.8 kg/ha) and K (12.7 kg/ha) by the crop compared to weedy check (21.2, 2.6 and 3.7 kg/ha), respectively. Among the integrated treatments, application of pendimethalin + imazethapyr (RM) at 1500 g ha^-1 + one hoeing at 3-4 leaf stage recorded maximum nitrogen, phosphorus and potassium uptake by seed and haulm and was found to be at par with weed free check. This might be due to better development of crop resulting from lesser crop weed competition, further, the higher content and higher dry matter accumulation by crop under these treatments boosted the nutrient uptake. Lower nitrogen, phosphorous and potassium uptake was recorded in unweeded control due to poor root growth and establishment as a consequence of severe crop-weed competition.  Significantly lower value of growth parameters viz. number and dry weight of nodules, seed yield were recorded in weedy check treatment. This might be due to severe competition by weeds for resources, which made the crop plant inefficient to take up more moisture, nutrients and ultimately growth was adversely affected due to less supply of carbohydrates.
 

 

 

       
The monetary returns were found to be significantly influenced by different weed control treatments (Table 3). The maximum net returns of Rs. 25264 /ha and additional returns over control Rs. 20875 were obtained with pendimethalin + imazethapyr (RM) at 1500 g ha^-1 as pre-emergence supplemented with one hoeing at 3-4 leaf stage. Among all the weed control treatments, maximum B-C ratio (2.02) was recorded with treatment pendimethalin + imazethapyr (RM) at 1500 g ha^-1 as pre-emergence. All the weed management strategies were almost equally important in controlling weeds and improving the crop yield. Weed free treatment was superior most with respect to growth parameters, seed yield (44,145 kg ha^-1) and quality. The next best treatment with respect to net returns (Rs. 25264/ha) and B:C ratio (2.02) was pendimethalin + imazethapyr (RM) at 1500 g ha^-1 as pre-emergence with one hand hoeing at 3-4 leaf stage and PRE pendimethalin + imazethapyr (RM) at 1500 g ha^-1, respectively. So, Pendimethalin + imazethapyr (RM) at 1500 g ha^-1 + one hoeing at 3-4 leaf stage was observed to be the best treatment in terms of yield, nodules, chlorophyll content as well as in monetary terms.
 

The findings of the present study provide herbicide options for the management of predominant weed flora in fenugreek. Research study indicate that alone PE or PoE herbicide treatments are not effective against effective weed management in this legume crop. The farmers can adopt this strategy to tackle the problem of poor efficacy of herbicides in particularly in north-western Indo- Gangetic Plains of India. However, growers and land managers will face increasing pressure to reduce overall pesticide use in food and feed production systems. There are myriad research and development needs for growers and land managers to successfully transition to a limited herbicide world. The metric for successful integrated weed management is lowest weed seed banks as possible concurrent with reduced herbicide use. In area there is paucity of labour, it is advisable to apply pendimethalin + imazethapyr (RM) at 1500 g ha^-1 as pre-emergence supplemented with one hoeing at 3-4 leaf stage under Haryana conditions.

None.