Post-Emergence Herbicides for Effective Weed Management, Enhanced Wheat Productivity, Proﬁtability and Quality in North-Western Himalayas: A ‘Participatory-Mode’ Technology Development and Dissemination

: ‘Participatory-mode’ adaptive research was conducted in wheat in north-western Himalayas (NWH) during 2008–2014 to develop an improved chemical weed management (ICWM) technology. First of all, two years ‘on-farm experimentation’ was performed in a randomized block design at 10 locations in NWH using seven treatments (Clodinafop @ 60 g a.i./ha (Clod); Clod followed by 2,4-D (Na-salt) @ 1.0 kg a.i./ha (Clod-fb-D); Isoproturon 75 WP @ 1.0 kg a.i./ha (Iso); Iso + D; Sulfosulfuron 75% WG @ 25 g a.i./ha + Metsulfuron 5% WG @ 2 g a.i./ha (Sulf + Met); weed-free-check; and un-weeded-check). In this study, the post-emergence application of Sulf + Met reported the lowest weed-index and NPK depletion by weeds with higher weed control efﬁciency (86.4%), weed control index (81.1%) and herbicide efﬁciency index (2.62) over other herbicides. Sulf + Met exhibited signiﬁcantly higher wheat productivity (3.57 t/ha), protein yield, net-returns and water-productivity, which was followed by Iso + D and Clod-fb-D, all of which remained statistically at par with each other. An impact assessment of intensive technology-transfer programme (2008–2014) revealed a higher technology adoption rate (71–98%) of ICWM leading to higher wheat productivity (~22%) and net income gains (2.8–26.4%) in NWH. Overall, Sulf + Met proved highly effective against mixed weed ﬂora in wheat to boost wheat productivity, proﬁtability, quality and water productivity in addition to a higher technology adoption rate and NIGs to transform rural livelihoods in NWH.


Introduction
India (Triticum aestivum L.) is the second largest producer of wheat in the world after China and accounts for~13.5% of global wheat production [1]. It is the second most important foodgrain crop in India after rice, providing~50% of total calories and protein requirements for a vast majority of the Indian population [2]. The total area under wheat in India is about 29.3 million ha (m ha) with production of 103.6 million tonnes (mt) and average productivity of 3.53 t ha −1 [1]. In India, wheat is grown over a wide range of latitudes (60 • N to 60 • S) and altitudes ranging from sea level to upto 3500 m in the tropics and subtropics [3]. Winter temperatures of 10 to 15 • C and summer temperatures varying from 21 to 26 • C are ideal for wheat production. Hence, it also grows well in north-western Himalayan provinces of India namely, Himachal Pradesh, Jammu and Kashmir, and Uttarakhand but with poor productivity (1.94 t ha −1 ) far below the national average [4,5]. Weed menace is a major production constraint in wheat in north-western Himalayas (NWH) in general and Himachal Pradesh in particular as a majority of hill farmers follow poor weed management practices, causinga~66% yield reduction in wheat depending upon the weed densities, type of weed flora and its infestation duration [6]. In Himachal Pradesh (Figure 1), about two thirds of arable land area contributes as a moderate to major wheat producing area (Figure 2a). We can transform~80% of the arable wheat suitability area in the state from a moderate to major wheat producing area simply by following a sound chemical weed management technology (Figure 2b). In NWH, Phalaris minor, Avena ludoviciana, Lolium temulentum and Poa annua are the major grassy weeds; while Vicia sativa, Anagallis arvensis, Ranunculus arvensis and Coronopus didymus are the main broad-leaved weeds that grow in association with wheat crop. These weeds germinate even before wheat germination and flourish luxuriously, taking advantage of its slow initial growth in NWH. Thus, weed competition throughout the crop season reduces wheat yield drastically if not managed scientifically [6]. Conventional cultural and manual weed management (CCMWM) practices are time-consuming and labour-intensive; hence, chemical weed management is most cost-effective and easy compared to manual weeding [7,8]. Chemical weed management has also become highly essential over the CCMWM practices in NWH due to an emerging labour shortage in these under-privileged ecosystems owing to rural migration to urban areas for better livelihoods [9,10]. Thus, a labour shortage vis à vis the costly manual labour required for CCMWM practices is hindering the wheat cultivation especially, in the complex weed-flora-dominated areas in NWH.  In general, the tank-mix combination of Isoproturon and 2,4-D has been recommended for chemical weed management in wheat in NWH [11]. However, the complex weed flora dominated by grassy weeds, namely Phalaris minor, Avena ludoviciana, Lolium temulentum and Poa annua, is not effectively controlled by the combination of Isoproturon + 2,4-D. Some suitable combinations of recently evolved broad-spectrum post-emergence herbicides, namely, Clodinafop Proprgyl in combination with 2,4-D or Sulfosulfuron + Metsulfuronmethyl, may effectively control the mixed weed flora of wheat in NWH. Clodinafop Propargyl has also been found to be effective against Isoproturon-resistant Phalaris minor and Avena fatua in wheat in NWH [6]. It is absorbed through the leaves and shoots with no harmful effects on the wheat and the succeeding crops. Likewise, Sulfosulfuron has been reported to have effective control of Isoproturon-resistant Phalaris minor, alongwith marginal control of broad-leaf weeds of wheat, while Metsulfuron-methyl has been recommended for the control of broad-leaf weeds in winter cereals [12], indicating that a combination of Sulfosulfuron + Metsulfuron-methyl may prove effective against the complex weed flora of wheat. Thus, an 'on-farm' experimentation was undertaken to assess the suitability of various post-emergence herbicides to effectively control the complex weed flora of wheat, and thereby develop an alternative chemical weed management strategy for enhancing wheat productivity, profitability, quality and resource-use efficiency in NWH. In addition, an intensive technology transfer programme was also aimed at higher technology adoption for improved wheat productivity and income gains in NWH.

Experimentation Site and Methodology Followed
A field investigation was performed in wheat during Rabi 2008-2009to Rabi2013-2014 by CSK Himachal Pradesh Agricultural University (CSKHPAU), Farm Science Centre, (FSC) Sundernagar, India, situated in north-western Himalayas (NWH). For the initial two years (Rabi 2008(Rabi -2009(Rabi to 2009(Rabi -2010, an 'on-farm experimentation (OFE)' was performed in the Mandi district of Himachal Pradesh province of India, which was selected randomly as the study area after randomly selecting Himachal Pradesh as the study province in NWH ( Figure 1). The intensive technology transfer programme comprised two years of OFE, frontline demonstrations (FLDs), method demonstrations, farmers' training, field conventions and other extension activities for technology dissemination on farmers' fields and its impact assessment as well. An assessment of pre-and post-training knowledge upgradation (Rabi 2008(Rabi -2009(Rabi to 2009(Rabi -2010, and technology adoption rate after one year of OFE (Rabi 2010-11), and then a technology impact assessment with respect to (w.r.t.) net income gains (NIGs) in the study area for the next three years (Rabi 2011-2012 to 2013-2014) were performed following an operational area framework methodology using standard procedures [10,13]. The reason for selecting the Mandi district as the study area was its unique geographical location (Figure 1) [14]. Soil organic carbon (SOC), textural class, soil pH and available NPK of the OFE sites (0-15 cm soil depth) were determined using standard procedures as shown in Table 1. On average, soils of the OFE locations were silty-clay loam (acid Alfisol) in texture and acidic in reaction (pH 6.6-6.9), with medium SOC (7.3-9.5 g kg −1 soil), medium available-N (283.5-322.8 kg ha −1 ), high available-P (16.8-21.3 kg ha −1 ) and high available-K (261.5-278.7 kg ha −1 ) before experimentation (Table 1).

Weed Studies
Weed count and weed dry biomass were recorded at 120 DAS by using a 0.25 m 2 sized quadrate randomly at three places in each net plot and expressed as a number per m 2 and g per m 2 , respectively, and then subjected to (square root transformation) for statistical analysis.
Weed control efficiency was determined using the standard procedure suggested by Das et al. [8] as follows: where WDc is the weed density (number per m 2 ) in the control plot (un-weeded check) and WDt is the weed density (number per m 2 ) in treated plot. Weed control efficiency (WCE) was determined using the standard procedure suggested by Das et al. [8] as follows: where WDMc is the weed dry matter (kg ha −1 ) in control plot (un-weeded check) and WDMt is the weed dry matter (kg ha −1 ) in treated plot. Weed index (WI) was determined using the standard procedure suggested by Das et al. [8] as follows: where Ywf is the crop yield in the weed-free plot (kg ha −1 ) and Yt is the crop yield (kg ha −1 ) in the treatment plot for which WI is to be determined. Herbicide efficiency index (HEI) was determined using the standard procedure suggested by Krishnamurthy et al. [21] as follows: Herbicide e f f iciency index (HEI) = where Yt is crop yield from the treated plot (kg ha −1 ); Yc is crop yield (kg ha −1 ) from the weedy-check plot; WDMt is the weed dry weight (kg ha −1 ) in the treated plot; and WDMc is the weed dry weight (kg ha −1 ) in the weedy-check plot.

Weed Chemical Analysis and Nutrient Depletion by the Weeds
To assess the effect of various weed management treatments on total weed dry matter (WDM) production at wheat harvest, the weed samples were again taken randomly by throwing a metallic quadrate of an area of 0.25 m 2 (0.25 m × 0.25 m) at two places in net-plots [8]. Then, the collected weed samples were first sun-dried and then oven-dried at 70 • C till constant weight and converted to total WDM (kg ha −1 ) at wheat harvest during both years. Nutrient concentrations (% N, P & K) in these weed samples vis à vis NPK nutrient depletion (kg ha −1 ) by these weeds (at wheat harvest) were determined using standard procedures [22].

Plant Growth, Yield Attributes, Crop Productivity and Profitability
Plant observations related to plant height and yield attributes, namely, spike length, number of grains per spike and 1000-grain weight were recorded from 10 randomly selected plants from each net plot at each location using standard procedures [22]. For recording the number of spikes m −2 in the wheat crop, three observational units of one meter row length each were selected randomly from the net-plot rows and counted accordingly, and then the mean value was converted into a number of spikes m −2 [22]. Likewise, the grain, straw and biological yield from the net-plots of wheat harvested at physiological maturity were determined using standard procedures. The cost of cultivation (COC) in INR ha −1 was calculated using prevailing market prices of inputs and outputs during the respective crop season. Gross returns were calculated using the prevalent market price of the wheat grains (INR 10,000 t −1 ) and straw (INR 1500 t −1 ) in the market. Net returns (INR ha −1 ) were calculated after subtracting the COC from the respective gross returns [23]. The benefit: cost ratio for each crop season was calculated by dividing the respective gross returns by the respective COC [23].

Plant Chemical Analysis and Protein Estimation
Wheat grain samples collected after harvest from all the field plots were oven-dried at 60 ± 2 • C for 72 h and then ground in a Willey Mill fitted with stainless steel parts and passed through a 1 mm sieve. The N concentrations in these grain samples were estimated by the Micro-Kjeldahl method [15]. The protein content (%) in the wheat grains was determined by multiplying respective grain N concentrations (%) by a factorof6.25. Water-use efficiency (WUE), Irrigation water productivity (IWP) and economic water productivity (EWP) were determined using standard procedures [25,26].

Technology Tranfer Methodologies
In order to achieve the objectives of the technology transfer on improved chemical weed management (ICWM) technology in wheat and its adoption in the study area, various technology transfer tools, namely, frontline demonstrations (FLDs), method demonstrations, farmers' specialised training, field days, field conventions, phone-line advisory to farmers, farmer-farmer extension approach, TV telecasts, media releases and SMS service, etc., were employed in the current study. Thus, in addition to conducting the OFE, the farmers (n = 102) of participating/surrounding villages were trained through FLDs, handson training on ICWM through method demonstrations, training, phone-line advisory, TV telecasts, media releases and regular SMS service, etc. for technology dissemination during 2008-2010. Literature on ICWM in simple local language (Hindi) was also provided in training for occasional technical back-up in NWH.

Knowledge Behaviour, Technology Adoption Rate and Impact Assessment
A thorough study was undertaken with well-structured interview schedules (pre-OFE training and post-OFE training) to assess the knowledge level and its upgradation among trainee farmers (n = 102) during 2008-2010.The extent of ICWM adoption was ascertained after one year of 'on-farm' experimentation, i.e., 2011-2012, after generating primary data using a participatory rural appraisal (PRA) technique, interview schedules and a group dynamics method to obtain reliable and valid information [13,14]. The net income gains (NIG) by the adoption of ICWM among practicing farmers in NWH were also assessed during Rabi 2011-2012 to 2013-2014 following the standard procedure suggested by Choudhary and Rahi [10].

Statistical Analysis
Statistical analysis of two years of 'on-farm' experimental data was conducted under a randomised block design (7 treatments; 10 locations/replications) using standard procedures as suggested by Gomez and Gomez [27] following the SPSS statistical package. Critical difference (CD) values at p = 0.05 were used to determine the significant differences among treatment means.

Weed Flora of Wheat in NWH and Herbicidal Options
In wet-temperate NWH, dominant weed spp. Were Phalaris minor, Avena ludoviciana, Lolium temulentum and Poa annua among narrow leaf weeds (NLWs), and Vicia sativa, Anagallis arvensis, Ranunculus arvensis and Coronopus didymus among broadleaf weeds (BLWs), which grew in association with wheat across the study years (Figures 3 and 4). Other weeds of minor importance were Lathyrus aphaca, Alopecurus myosuriodes, Stellaria media, Polygonum alatum and Plantago sp. Thus, there is predominance of mixed weed flora in wheat in NWH, where the sole use of herbicides having efficacy either against NLWs or BLWs is not advisable; rather, we need to develop a broad-spectrum NLW and BLW management strategy [5]. A post-emergence application of Isoproturon has already shown resistance against many biotypes of Phalaris minor and Avena fatua in wheat in NWH [6,28]. For ensuring broad-spectrum weed management, we can use new herbicidal combinations like Sulfosulfuron 75% WG + Metsulfuron 5% WG (Sulf + Met) or Clodinafop followed by 2,4-D (Na salt) [Clod-fb-D) over the conventional herbicidal combination of Isoproturon 75 WP + 2,4-D (Na salt) (Iso + D). Clodinafop Propargyl effectively controls the Isoproturon-resistant Phalaris minor, but again, few biotypes of Phalaris minor have recently shown cross-resistance to it in different parts of north India [6]; therefore, its use may be restricted to areas where cross-resistance has not appeared. Further, the emerging labour shortage in these under-privileged ecosystems due to rural migration to urban areas emphasizes the need to develop a sound chemical weed management technology for wheat to boost wheat productivity and farm incomes in NWH. Hence, the above discussion strongly advocates for assessing the bio-efficacy of an herbicidal combination of Sulfosulfuron 75% WG + Metsulfuron 5% WG both against BLWs and NLWs, in addition to addressing the emerging herbicide resistance in Phalaris minor in NWH [6,12].

Weed Count and Weed Dry Matter Studies
A post-emergence application of Clod-fb-D resulted in the significantly lowest weed count of Phalaris minor and Lolium temulentum, which was followed by Sulf + Met (Table 2; Figure 3). Avena ludoviciana and Poa annua observed the lowest weed count using Sulf + Met followed by Clod-fb-D. Thus, Clod-fb-D is highly effective against Phalaris minor, Lolium temulentum and poa annua, while Sulf + Met is more effective for Avena ludoviciana and Poa annua management. Sulf + Met also exhibited the lowest weed count in all BLWs, namely,Vicia sativa, Anagallis arvensis, Ranunculus arvensis and Coronopus didymus which was followed by Iso + D and Clod-fb-D, respectively (Table 2; Figure 4), indicating that Sulf + Met is a better option for the effective control ofall BLW flora. The sole use of either Isoproturon or Clodinafop is not effective against the mixed weed flora of wheat, especially BLWs [8,29,30].    Total weed dry matter (TWDM) production of NLWs and BLWs at 120 DAS was significantly influenced by different herbicide treatments over un-weeded check (UWC), and followed the trend of Sulf + Met < Iso + D < Clod-fb-D < Iso < Clod > UWC, respectively (Table 2; Figure 5).Essentially, Sulf + Met proved superior for effectively controlling the mixed weed flora with the least species-wise weed population, total NLW and BLW population and TWDM during both years (Table 2; Figures 3 and 4). This may be attributed to the inhibition of enzyme acetolactate synthase (ALS) by the application of Sulf + Met, which acts as a catalyst in the biosynthesis of branched-chain amino acids such as valine, leucine and isoleucine [31], and is thereby responsible for the higher effectiveness of Sulf + Met in selectively killing both NLWs and BLWs over Iso + D, Clod-fb-D as well as the sole application of Clodinafop-propargyl or Isoproturon [31][32][33].

Weed Control Indices and Herbicide Efficiency Index
The post-emergence application of Sulf + Met exhibited higher weed control efficiency (WCE) after a weed-free check (WFC), while the sole use of Clodinafop exhibited the least WCE during both years (Figures 6 and 7). WCE followed the trend of WFC > Sulf + Met > Clod-fb-D > Iso + D > Iso > Clod, respectively, indicating that Sulf + Met is highly effective against the mixed weed flora of both NLWs and BLWs, followed by Clod-fb-D and Iso-D. The weed control index (WCI) followed the trend of WFC > Sulf + Met > Iso + D > Clod-fb-D > Iso > Clod, respectively, which again indicated the superiority of Sulf + Met for effective NLW and BLW management after WFC, which was followed by Iso + D and Clod-fb-D.  The UWC exhibited the comparatively highest weed index (WI), owing to the lowest wheat grain yield during both years (Figure 8). WI followed the trend of Sulf + Met < Iso + D < Clod-fb-D < Iso < Clod < UWC, respectively, which indicates that Sulf + Met may harness higher wheat productivity owing to the least weed completion due to the effective management of both NLWs and BLWs over Iso-D and Clod-fb-D, respectively (Figure 8). The herbicide efficiency index (HEI) followed the trend of Sulf + Met > Iso + D > Clod-fb-D > Iso > Clod, owing to higher wheat grain yield and the least TWDM in wheat over other treatments [8], thus indicating that Sulf + Met is superior w.r.t. HEI over Iso + D and Clodfb-D (Figure 9). The weed eradication in WFC plots enumerated significantly higher WCI and WCI in this treatment [22], while the excellent weed knockdown ability of Sulf + Met both against complex weed flora including Isoproturon-and Clodinafop-resistant NLWs could be assigned as the reason for superior weed indices, namely, WCE, WCI and WI as well as higher HEI by the application of Sulf + Met over other herbicidal treatments [31].The combined application of Sulf + Met exhibits both foliar and soil activity against weeds that inhibits cell division in shoots and roots by inhibiting the ALS enzyme and thereby blocks amino acid biosynthesis; hence, the weed plants suffer selectively [31,34]. This mechanism impairs the phloem transport in the weed plants with stunted growth on account of the cessation of cell division and slow plant death, thus providing excellent control of both dicot and monocot weeds by reducing their densities and TWDM [34,35].

Weed Nutrient Concentrations and Weed Nutrient Depletion
Average nutrient concentrations (NPK) in mixed weed flora samples taken at wheat harvest followed the trend of Sulf + Met > Iso + D > Clod-fb-D > Iso > Clod > UWC, respectively, during both years ( Figure 10). NPK concentrations in weed samples remained statistically at par among different herbicide treatments, except UWC, which exhibited the lowest values. NPK depletion by these weeds at wheat harvest followed the reverse trend of UWC > Iso > Clod > Clod-fb-D > Iso + D > Sulf + Met, respectively, where UWC exhibited the significantly highest NPK depletion, while Sulf + Met remained at par with Iso-D and Clod-fb-D exhibited the least NPK depletion (Figure 11). Since Sulf + Met is highly effective against the mixed weed flora of both NLWs and BLWs over Clod-fb-D or Iso + D, it observed higher weed nutrient concentrations due to the least inter-and intra-spp. competition [36][37][38]. Conversely, the lowest weed count of both NLWs and BLWs under Sulf + Met exhibited the lowest TWDM per m 2 land area that computed the lowest weed nutrient depletion under Sulf + Met over other herbicidal treatments ( Figure 11).

Growth, Yield Attributes, Wheat Productivity and Quality
Plant height, the number of spikes m −2 and grains spike −1 in wheat were significantly higher under Sulf + Met, which remained at par with Iso + D and Clod-fb-D, while the sole use of Isoproturon or Clodinafop exhibited the least magnitude of these parameters during both years (Table 3). Spike length and 1000-grain weight also exhibited higher values under Sulf + Met. Grain, straw and the biological yield of wheat followed the trend of WFC > Sulf + Met > Iso + D > Clod-fb-D > Iso > Clod > UWC, respectively, during both years (Table 4). On average, Sulf + Met exhibited an approximate1.1, 5.1, 11.2 and 15.2% higher grain yield over Iso + D, Clod-fb-D, Isoproturon and Clodinafop, respectively. Harvest index and protein content in wheat grains exhibited a non-significant influence under different weed management treatments, while protein yield was significantly influenced by these treatments (Table 4). Protein content and protein yield followed the trend of WFC > Sulf + Met > Iso + D > Clod-fb-D > Iso > Clod > UWC, respectively, during both years. On average, Sulf + Met exhibited an approximate5.1, 10, 18.5 and 25.3% higher protein yield over Iso + D, Clod-fb-D, Isoproturon and Clodinafop, respectively. In general, WFC plots attained better growth due to the elimination of NLWs and BLWs in addition to better availability of space, moisture, nutrients and light, which in turn had superior yield attributes and consequently higher wheat yield, protein content and protein yield in WFC [36]. Similarly, Sulf + Met exhibited a relatively higher knockdown effect on NWLs and BLWs owing to the inhibition of ALS enzyme-impairing amino acid biosynthesis selectively killing the weeds and reducing crop-weed competition for space, light and nutrients, which collectively led to better growth and yield attributes (spikes m −2 , grains spike −1 ) in wheat, resulting in a higher wheat yield and protein yield over other herbicidal combinations [35,36]. Thus, the low weed infestation in Sulf + Met and WFC helped in accumulating more biomass in wheat plants owing to better nutrient and water acquisition and optimum photosynthesis as a result of low crop-weed competition for light and space, which resulted in better yield expression in wheat [31,35,39,40]. The solitary use of a single herbicide resulted in lesser grain and straw yield in wheat due to poor weed control and higher crop-weed competition [36][37][38]41].

Production-Efficiency, Monetary-Efficiency and Water Productivity
Production efficiency (PE) and monetary efficiency (ME) followed the trend of WFC > Sulf + Met > Iso + D > Clod-fb-D > Iso > Clod > UWC, respectively, indicating the superiority of Sulf + Met, followed by Iso + D and Clod-fb-D, all of which remained statistically at par during both years (Table 6). Total water use (TWU) was the same among different treatments; however, total water productivity (TWP), irrigation water productivity (IWP) and economic water productivity (EWP) followed the trend of WFC > Sulf + Met > Iso + D > Clod-fb-D > Iso > Clod > UWC, respectively, during both years (Table 6). Hence, WFC proved significantly superior among different weed management options, though it behaved statistically at par with Sulf + Met and Iso + D w.r.t. TWP, IWP and EWP in the current study. The effective control of complex weed flora under Sulf + Met and WFC exhibited better yield expression and resultant economic performance, which led to improved PE, ME and water productivity in these treatments over the rest of the herbicidal treatments [31,35].

Knowledge Upgradation and Technology Adoption Rate
Pre-training knowledge behaviour of farmers (n = 102) in different CBDs of participating and surrounding villages of the study area in NWH revealed that farmers' knowledge about chemical weed management (CWM) practices varied between 7-48%, which was upgraded to 78-100% after imparting training (Table 7). Among CWM practices, the pretraining knowledge level was lowest (7%) about herbicide resistance as well as about the agronomic measures for herbicide resistance avoidance, both of which upon training were improved to 78 and 99%, respectively. The pre-training knowledge level of conventional cultural and manual weed management (CCMWM) practices varied between 23-81% among trainee farmers (n = 102) which was upgraded to 91-100% after imparting training.  Among CCMWM practices, the trainee farmers had the lowest knowledge level (23%) of crop rotations and intercropping systems for wheat, which upon training was upgraded to 91%. The highest pre-training knowledge level was~81% and about agronomic weed management operations, which was improved to 97% after imparting training. The technology adoption rate after one year of OFE execution varied between 71-98% about CWM practices, with the lowest adoption rate (71%) for agronomic measures to reduce herbicide resistance and the highest adoption rate (98%) for the application of various chemical herbicides for CWM in wheat ( Table 7). The technology adoption rate for CCMWM practices varied between 72-95%, with the lowest values (72%) for summer ploughing and crop residue retention, while the highest adoption rate (95%) was observed for agronomic weed management operations in wheat in NWH ( Table 7). The higher post-training knowledge upgradation (n = 102) and higher technology adoption rate revealed that operational area framework-based intensive technology transfer programmes may lead to faster and higher knowledge upgradation and technology adoption amongst target farmers [10,[44][45][46].

Impact Assessment and Net Income Gains
Based upon the OFE, finally an improved chemical weed management technology (ICWM) was developed against the mixed weed flora of wheat in NWH i.e., post-emergence application of Sulfosulfuron 75% WG @ 25 g a.i./ha + Metsulfuron 5% WG @ 2 g a.i./ha after 25-30 DAS of wheat. This ICWM technology was then extensively transferred in wettemperate NWH to effectively control the NLWs and BLWs of wheat for harnessing higher wheat productivity with better quality, profitability and water productivity in addition to curtailing the herbicide resistance issues that emerged due to conventionally used herbicides in NWH. During 2008-2010, CSKHPAU-FSC, Sundernagar (India) conducted 20 OFEs in 10 villages/locations of three CBDs of the Mandi district in NWH for two years in addition to numerous frontline demonstrations (FLDs), method demonstrations, farmers' training, field days, TV telecasts, media releases, field conventions, phone-line advisory, regular SMS service, etc. for technology dissemination on farmers' fields. The CBD-wise available information (based on primary and secondary data) revealed that in the Mandi district of Himachal Pradesh alone, the adoption of CWM practices were scaled-up from 48% in 2008 to 98% in the year 2014, which improved wheat productivity by~22% (2008-2009 to 2013-2014). Numerous operational area framework-based 'on-farm' experimentation and intensive technology transfer programmes have brought high success rates in technology adoption and productivity enhancement worldwide [13,14,44,[47][48][49]. An assessment of net income gains (NIG) by the adoption of ICWM technology in wheat was performed in the study area for three years (2011-2012 to 2013-2014) through wellstructured interview schedules (Table 8). The NIG analysis revealed that net returns from conventional cultural and manual weed management (CCMWM) practices ranged between INR 18,667-21,580 ha −1 , with an average value of INR 20,764 ha −1 among TWM practicing farmers (n = 30) out of the 102 trained farmers (n = 102). Net returns from CCWM practices ranged between INR 21,530-27,962 ha −1 , with an average value of INR 27,411 ha −1 among practicing farmers (n = 102) receiving NIG gains of 24.2% over CCMWM in the study area. The ICWM technology Sulfosulfuron 75% WG @ 25 g a.i./ha + Metsulfuron 5% WG @ 2 g a.i./ha, was the best performer, with net returns ranging from INR 22,365 to 29,522 ha −1 , with an average value of INR 28,198 ha −1 receiving~26.4% and 2.8% higher NIGs over CCMWM and CCWM, respectively, in wheat in north-western Himalayas (Table 8). Higher NIG gains through the adoption of sound farm technologies have also been reported by many researchers for bringing socio-economic transformation in livelihoods of hill farmers of NW Himalayas [9,10,13,14].

Conclusions
Post-emergence application of Sulfosulfuron 75% WG @ 25 g a.i./ha + Metsulfuron 5% WG @ 2 g a.i./ha (Sulf + Met) emerged as an improved chemical weed management (ICWM) technology against the mixed weed flora of wheat in NWH. Sulf + Met exhibited significantly higher weed control efficiency (86.4%), weed control index (81.1%) and herbicide-efficiency index (2.62) in addition to lower weed nutrient depletion over other herbicidal treatments. Sulf + Met reported significantly higher wheat productivity (3.57 t ha −1 ), protein yield (0.44 t ha −1 ), net returns (INR 28,569 ha −1 ) and water productivity. The Iso + D and Clod-fb-D were another two viable herbicidal combinations to manage complex weed flora of wheat in NWH; however, their repeated use may lead to development of Isoproturon-and Clodinafop-resistant Phalaris minor biotypes as per the reports from NWH. The impact assessment of intensive technology transfer programme revealed higher knowledge upgradation (78-100%), a higher technology adoption rate (71-98%) and improved wheat productivity (~22%) in NWH. The adoption of ICWM technology also enhanced the NIG by~26.4 and 2.8% over CCWM and CCMWM in wheat in NWH, which advocates for employing 'participatory-mode' adaptive research and technology transfer programmes in remote agro-ecologies. Essentially, Sulf + Met proved a potential ICWM technology against the mixed weed flora of wheat for boosting the crop and water productivity, profitability and quality of wheat in NWH.