Long-duration pigeonpea is widely cultivated in Bihar on marginal and sub-marginal land without fertilizers under rainfed conditions. Its yield remains unstable and uneconomical due to monsoon vagaries, slow initial growth, low productivity and long duration. Weeds also compete heavily because of its slow growth and unutilized inter-row space (Barod et al., 2017). Similar constraints in pigeonpea productivity under rainfed ecosystems have been highlighted by several studies, emphasizing the need for improved crop management practices (Pandey et al., 2021).
       
Plant arrangement plays a crucial role in shaping the crop environment and influencing yield. Strategic row placement of main and intercrops in proper proportion ensures efficient use of space, nutrients, sunlight, and soil moisture, thereby enhancing system productivity (Kasbe et al., 2010). Intercropping systems involving pigeonpea have been reported to improve resource use efficiency and overall productivity under rainfed conditions when appropriate spatial arrangements are followed (Garud et al., 2019). The effectiveness of intercropping depends on factors such as crop duration, growth rate, planting density and root characteristics, which determine competition for nutrients, moisture and space and ultimately input use efficiency.
       
The level of competition in pigeonpea intercropping varies with planting patterns and the choice of intercrops due to their distinct growth and nutrient uptake habits. Hence, soil fertility must be managed carefully through proper nutrient application. Manual weeding, though common in India, is labor-intensive and costly, while herbicides offer a cheaper alternative but are limited by selectivity. A single herbicide cannot control all weeds, which differ in morphology, physiology and emergence and may also cause weed shift and resistance. Herbicide mixtures (Das, 2008) provide broader control, prevent weed shift and delay resistance. Similar findings on integrated weed management improving crop productivity and economics in pigeonpea-based systems have been reported (De et al., 2018).
       
To study the effect of planting pattern and weed management on productivity and economics of pigeonpea intercropping under rainfed conditions, the present investigation was planned to be conducted.

A field experiment was conducted during the kharif seasons of 2021-22 and 2022-23 at Tirhut College of Agriculture, Dholi (25°98′N, 85°76′E, 51.3 m above msl), Dr. Rajendra Prasad Central Agricultural University, Pusa, Samastipur, Bihar. The soil was sandy loam, low in organic carbon (0.33%), available N (163.8 kg ha^-1) and P (12.2 kg ha^-1) and medium in K (152.8 kg ha^-1) with pH 8.1. The experiment was laid out in a factorial randomized block design with three replications. Treatments included two intercropping systems with two planting methods [pigeonpea (60 cm) + soybean (1:1), pigeonpea (60 cm) + urdbean (1:1), pigeonpea paired (45 cm) + soybean (2:2), pigeonpea paired (45 cm) + urdbean (2:2)], three fertilizer levels of intercrops (50%, 75% and 100% RDF) and four weed management practices [weedy check, hand weeding at 20 and 40 DAS, imazethapyr 75 g ha^-1 + quizalofop ethyl 60 g ha^-1 at 25 DAS and chlorimuron ethyl 6 g ha^-1 (PPI) followed by imazethapyr 75 g ha^-1 at 25 DAS], along with sole crops of pigeonpea, soybean and urdbean.
       
The pigeonpea variety ‘Rajendra Arhar 1’, soybean ‘P 1241 TL’ and urdbean ‘Pant U-31’ were sown in the last week of July. Sole crops were planted at 60 cm (pigeonpea), 45 cm (soybean) and 30 cm (urdbean) row spacing, maintaining plant-to-plant distances of 20, 5 and 10 cm, respectively, by thinning three weeks after sowing. The recommended fertilizer doses were 20:40:20:20 kg NPKS ha^-1 for pigeonpea, 25:25:20 kg NPK ha^-1 for soybean and 20:40:20 kg NPK ha^-1 for urdbean. In intercropping systems, pigeonpea received full RDF, while intercrops received fertilizers as per treatments. Full doses of N, P, K and S were applied at sowing. Urdbean and soybean were harvested in October-November, while pigeonpea was harvested in April. Weed control chemicals were applied using a knapsack sprayer with flat-fan nozzle as per treatment schedules.
       
Weed population and dry weight were recorded at 60 DAS using a 0.25 m² quadrat placed randomly at two places in each plot and data were subjected to square root transformation (√X + 0.5) prior to analysis. The experiment received 1796.6 mm rainfall in 2021-22 and 733.8 mm in 2022-23. To compare systems, yields were converted into pigeonpea-equivalent yield (PEY) based on prevailing market prices. Fruiting efficiency was calculated as the ratio of pod-bearing flowers to total flowers, expressed as a percentage. Net returns were obtained by subtracting cost of cultivation from gross return and the benefit: cost ratio (B:C) was computed as gross returns divided by cost of cultivation. Data for all parameters were analyzed using the procedure described by Cochran and Cox (1977) for randomized block design and treatment means were compared by ANOVA technique.

Weed flora of the experimental field consisted of Eleusine indica, Ageratum conyzoides, Scoparia dulcis, Ceanothus greggii, Phyla nodiflora, Eragrostis tenella, Cichorium intybus, Convolvulus arvensis, Parthenium hysterophorus, Canada thistle, Cannabis sativa, Anagallis arvensis.
 
Physiological and yield characteristics
 
Plant height did not vary significantly among intercropping systems and sole pigeonpea. However, pigeonpea + urdbean in paired row planting recorded significantly taller plants than pigeonpea + soybean in 2:2 ratio and intercropping in normal planting pattern (Table 1). Application of 100% RDF produced the tallest plants, which decreased with lower fertilizer levels. Maximum plant height was observed in hand weeding twice, which was at par with imazethapyr + quizalofop ethyl and significantly higher than pre-plant incorporation of chlorimuron ethyl fb imazethapyr (Dhane et al., 2010).


       
Yield indices such as branches plant^-1, pods plant^-1 and grains pod^-1 did not vary significantly among intercropping systems and sole pigeonpea (Table 1). Paired row pigeonpea + urdbean recorded significantly higher values of these indices (except grains pod^-1) than pigeonpea + soybean in the same planting pattern and their intercropping in normal planting. Pod length and grains/pod remained unaffected. Improved yield indices in pigeonpea + urdbean can be attributed to reduced competition for nutrients and light and the intercrop’s smothering effect on weeds initially, followed by improved light penetration at later stages (Kumawat et al., 2013).
       
Higher plant height and yield indices at 100% RDF may be due to sufficient nutrient availability, reducing competition and enhancing growth. Better values under hand weeding twice were likely due to complete weed eradication and soil loosening, facilitating aeration and nodulation, ultimately improving growth and yield attributes (Gupta and Saxena, 2008; Dhane et al., 2009).
 
Grain yield
 
Grain yield of pigeonpea did not differ significantly between intercropping and sole cropping (Table 1). However, paired row pigeonpea + urdbean produced higher yield (2087 kg/ha) than pigeonpea + soybean and normal intercropping, similar to findings of Kumar and Kushwaha (2018). Inclusion of urdbean reduced soil fertility depletion, suppressed weeds at early stages, and improved soil properties, thereby enhancing yield indices and grain yield. These findings are in close agreement with reports indicating that legume-based intercropping systems improve productivity and resource-use efficiency under rainfed conditions (Ghule et al., 2026). Yield also increased with fertilizer level, peaking at 100% RDF (2099 kg/ha), as adequate nutrients minimized competition between main and intercrops (Pandey et al., 2015). Maximum yield was obtained under two hand weedings (2344 kg/ha), significantly higher than post-emergence imazethapyr + quizalofop ethyl (2118 kg/ha) and PPI chlorimuron ethyl fb imazethapyr, due to effective weed suppression, better aeration, and nutrient availability. Similar results were reported by Wadafale et al. (2011). Yield also increased with fertilizer level, peaking at 100% RDF (2099 kg/ha), as adequate nutrients minimized competition between main and intercrops (Pandey et al., 2015). Maximum yield was obtained under two hand weedings (2344 kg/ha), significantly higher than post-emergence imazethapyr + quizalofop ethyl (2118 kg/ha) and PPI chlorimuron ethyl fb imazethapyr, due to effective weed suppression, better aeration, and nutrient availability. Similar results were reported by Wadafale et al. (2011).
 
Fruiting efficiency
 
Fruiting efficiency was significantly higher in paired row pigeonpea + urdbean (18.98%) than pigeonpea + soybean and their normal intercropping (Table 1). Maximum efficiency was recorded at 100% RDF (18.44%), which declined with lower fertilizer levels. Weed management also improved fruiting efficiency over weedy check, with hand weeding (18.84%) at par with imazethapyr + quizalofop ethyl and superior to PPI chlorimuron ethyl fb imazethapyr. The higher values in these treatments were attributed to better ground cover by component crops, weed suppression, moisture conservation and improved nutrient uptake, leading to reduced flower drop and greater pod set.
 
Pigeonpea equivalent yield
 
All intercropping systems in both planting patterns recorded significantly higher pigeonpea equivalent yield than sole pigeonpea (Table 1). Paired row pigeonpea + urdbean (2791 kg/ha) and pigeonpea + soybean (2598 kg/ha) out-yielded their normal planting, due to better production of both main and component crops, confirming earlier findings (Kumar and Kushwaha, 2018; Pandey et al., 2021). Pigeonpea equivalent yield also increased with fertilizer level, peaking at 100% RDF (2772 kg/ha), in line with Sekhon (2018). Weed management significantly improved productivity over weedy check, with hand weeding twice giving the maximum pigeonpea-equivalent yield (3016 kg/ha), followed by post-emergence imazethapyr + quizalofop ethyl (2740 kg/ha) and PPI chlorimuron ethyl fb imazethapyr (2553 kg/ha). Higher productivity under weed-free conditions was due to reduced crop–weed competition, ensuring better utilization of nutrients and moisture. These findings are in accordance with earlier reports indicating that effective weed management practices in pigeonpea-based intercropping systems significantly enhance yield and resource use efficiency (Sannagoudar et al., 2024). Harvest index was highest in paired row pigeonpea + urdbean and hand weeding twice, and increased significantly only up to 75% RDF, suggesting efficient partitioning of assimilates towards economic yield under optimal nutrient and weed management conditions.
 
Production efficiency, water productivity and water use efficiency
 
Paired row pigeonpea + urdbean recorded significantly higher production efficiency (11.63 kg/ha/day), water productivity (8.70 kg/m³) and water use efficiency (3.55 kg/ha/mm) than pigeonpea + soybean and normal intercropping (Table 2). Application of 100% RDF also gave higher values (11.55 kg/ha/day, 8.63 kg/m³ and 3.53 kg/ha/mm) compared to 75% and 50% RDF. Among weed management practices, hand weeding twice achieved the highest production efficiency (12.57 kg/ha/day), water productivity (9.39 kg/m³) and WUE (3.84 kg/ha/mm), followed by post-emergence imazethapyr + quizalofop ethyl (11.42 kg/ha/day, 8.53 kg/m³). The improvement in these parameters was attributed to higher grain yield and better utilization of available moisture and nutrients under reduced weed competition. These findings are in close agreement with earlier studies indicating that integrated nutrient and weed management practices significantly enhance productivity and water use efficiency in pigeonpea-based intercropping systems under rainfed conditions (Kumar et al., 2022).


 
Land-equivalent ratio
 
In intercropping systems, LER was >1 in both planting patterns, confirming higher biological efficiency (Table 2). Paired row intercropping recorded significantly higher LER, with maximum values in pigeonpea + urdbean (1.96) and pigeonpea + soybean (1.91). An LER of 1.96 indicates 96% more land under sole pigeonpea would be required to match the intercropping yield. LER also increased with fertilizer level, reaching 2.00 at 100% RDF. Among weed management practices, hand weeding twice gave the highest LER (2.13), followed by post-emergence imazethapyr + quizalofop ethyl (1.94), while pre-plant chlorimuron ethyl fb imazethapyr recorded the lowest (1.81).
 
Weed parameters
 
Pigeonpea + urdbean in both paired and normal planting significantly reduced weed count, dry biomass and improved weed control efficiency (WCE) compared to pigeonpea + soybean, confirming earlier results (Tomar et al., 2004). Application of 50% RDF also lowered weed density and biomass with higher WCE than 100% RDF (Kakabouki et al., 2022). Maximum weed density and biomass occurred in the weedy check, while hand weeding gave the lowest values. Among herbicides, post-emergence imazethapyr + quizalofop ethyl recorded minimum weed density, followed by pre-plant chlorimuron ethyl fb imazethapyr. However, WCE was highest under hand weeding, followed by post-emergence and pre-plant herbicidal treatments. The effectiveness of hand weeding was due to complete removal of emerged weeds, while the combined herbicide provided broad-spectrum control through different modes of action (Khazi et al., 2018; Sandya and Singh, 2018).
 
Microbial population and dehydrogenase activity
 
Intercropping of pigeonpea + urdbean and soybean in paired rows maintained significantly higher microbial population and dehydrogenase activity (Table 3) than normal planting, due to greater litter fall and decomposition providing carbon for microbes, which enhanced soil properties and plant growth (Imane et al., 2022; Kumar et al., 2022). Among nutrient levels, 50% RDF recorded higher microbial activity than 100% RDF, likely because moderate nitrogen fertilization stimulated microbial-derived carbon storage and nitrogen immobilization. Hand weeding twice also supported greater microbial population and activity than chemical weeding, as herbicides reduced microbes through toxicity and competition, though in some cases microbial growth increased due to commensalism or herbicide utilization as a carbon source (Ghosh et al., 2012; Maheswari and Ramesh, 2019; Sebiomo et al., 2011).


 
Economics
 
Intercropping recorded significantly higher net returns and B:C ratio than sole pigeonpea (Table 2). Net returns were highest in pigeonpea + urdbean (155.89 × 10³ ₹/ha) and pigeonpea + soybean (142.80 × 10³ ₹/ha), with pigeonpea + urdbean in paired rows significantly outperforming both 1:1 intercroppings (Table 3). The paired row system of pigeonpea + urdbean also registered the highest B:C ratio. Application of 100% RDF significantly increased net returns (155.17 × 10³ ₹/ha) and B:C ratio (4.33) over 50% RDF. Among weed control practices, hand weeding twice gave the highest net returns (159.72 × 10³ ₹/ha), while post-emergence imazethapyr + quizalofop ethyl recorded the highest B:C ratio (4.60). The superior returns in paired row pigeonpea + urdbean resulted from higher yields of both crops. Similar findings were reported by Singh et al., (2013); Pandey and Tiwari (2017) and Bali et al., (2016), highlighting the role of higher fertilizer levels and effective weed management in maximizing profitability. It is possible that the higher yield in hand weeded plots was due to a higher cost investment in hand weeding, as the net return and B:C ratio in chemical weeding were higher.
       
The interaction between nutrient levels and weed management practices significantly influenced system productivity and net returns of the pigeonpea-based intercropping system. Increasing fertilizer levels from 50% RDF to 100% RDF consistently enhanced pigeonpea equivalent yield and economic returns across all weed management treatments, indicating the superiority of integrated nutrient and effective weed management practices (Table 4). These findings are in close agreement with earlier reports highlighting that combined application of optimum fertilizer levels and efficient weed control measures significantly improves productivity and profitability of pigeonpea-based intercropping systems under rainfed conditions (Bhardwaj et al., 2023).

Paired row planting of pigeonpea + urdbean (45 cm) in 2:2 row ratio recorded significantly higher system productivity, net return and B:C ratio than their normal planting pattern and sole pigeonpea. Among weed management treatments, hand weeding twice (20 and 40 DAS) resulted in significantly higher system productivity, water productivity, production efficiency, but higher economic returns were associated with combined application of imazethapyr + quizalofop ethyl 75+60 g/ha at 25 DAS. Application of 50% RDF in weed management produced significantly higher system productivity and net return than 100% RDF in weedy check, indicating that weed management could save 50% RDF and enhance profitability.

Dr. Rajendra Prasad Central Agricultural University, Pusa, Bihar, provided the funding and facilities needed by the authors to conduct this study and the authors are grateful for their support.
 
Disclosure statement
 
There was no disclosure of possible competing interests by the authors.

The authors declare that there are no conflicts of interest regarding the publication of this manuscript. All authors have contributed significantly to the work and have approved the final version for submission. The authors confirm that there are no financial, personal, or professional relationships that could have influenced the work reported in this manuscript.