Physiological growth behaviour of pigeonpea (Cajanus cajan L.) under intercropping systems and integrated nutrient management

Introduction

Pigeonpea (Cajanus cajan (L.) Millsp.), a prominent grain legume of the semi-arid tropics, is extensively cultivated in India for its versatile role in food systems and soil health improvement. Belonging to the Fabaceae family, pigeonpea holds a special place in Indian agriculture due to its drought resilience, deep rooting system, and ability to thrive in marginal lands under rainfed conditions. India is the largest producer of red gram (Cajanus cajan) globally. During the 2023-24 cropping year, the country produced approximately 4.34 million tonnes of red gram, cultivated over an area of 5.05 million hectares, resulting in an average productivity of 859 kg per hectare (ANGRAU Redgram outlook Report, 2023-24). Red gram is extensively grown across various states, with Karnataka leading in area under cultivation (1.33 million hectares), followed by Maharashtra (1.11 million hectares), Uttar Pradesh (0.35 million hectares), Andhra Pradesh (0.23 million hectares), Gujarat (0.22 million hectares), and Jharkhand (0.185 million hectares) (agriwelfare.gov.in). The extended growth duration and wider plant spacing of the crop provide ideal conditions for intercropping, as the slow early growth creates sufficient inter-row space that can be effectively utilized by suitable companion crops to maximize land and resource use efficiency. In contrast, modern intensive agricultural systems have increasingly shifted toward simplified monocropping practices, coupled with excessive dependence on chemical fertilizers and pesticides to meet the growing demand for food production. However, this approach has led to significant farmland biodiversity loss and has negatively impacted the environment and ecosystem functions, posing serious threats to food security and long-term agricultural sustainability (Yu et al., 2025) [8] . Intercropping, a practice wherein two or more crops are cultivated simultaneously on the same piece of land, is a time-tested strategy in rainfed agriculture. The core idea behind intercropping is to maximize overall productivity per unit area and time, while also ensuring fair and efficient use of land, labor, and other farming resources (Boto and Bassa, 2025) [3] . In this study, four intercrops i.e., soybean, pearl millet, sesame, and sorghum were evaluated in combination with pigeonpea to assess the biological and economic viability of different intercropping systems. Each of these intercrops brings unique traits that contribute to the performance of the system. These various crop combinations i.e., legume + legume, legume + millet, legume + oilseed, and legume + cereal, each offer specific advantages that merit comparative evaluation under similar environmental and management conditions. The differences in rooting patterns, nutrient demands, and growth durations help in efficient resource partitioning, ultimately improving the stability and profitability of farming systems. Evaluating these systems helps in identifying the most suitable combinations for specific agro-climatic zones and resource availability. In addition to crop choice, nutrient management plays a pivotal role in determining the success of intercropping systems. Integrated Nutrient Management (INM), which involves the combined use of chemical fertilizers, organic manures such as farmyard manure (FYM), and bio-fertilizers, aims to maintain soil fertility while sustaining high crop yields. The rationale behind INM is to optimize the nutrient supply by harnessing the strengths of both organic and inorganic sources. For instance, pairing 50% of recommended fertilizer dose with vermicompost in pigeonpea + greengram systems increased yields by over 25% compared to chemical-only regimens (Sharma et al. 2010) [6] . In intercropping systems, where different crops may have varying nutrient requirements and uptake rates, INM helps in balancing nutrient availability throughout the cropping period. As part of improved agronomic practices under Integrated Nutrient Management (INM), foliar application of potassium nitrate (KNO₃) and naphthalene acetic acid (NAA) at the flower initiation stage in pigeonpea has gained prominence due to its positive physiological and yield-enhancing effects. Another critical aspect of this research is the adoption of the Broad Bed and Furrow (BBF) method of land configuration. In rainfed areas like Marathwada, where water availability is limited and rainfall is often erratic, conserving soil moisture becomes crucial for sustaining crop growth and productivity. Such structural interventions are especially important in Marathwada's semi-arid conditions, where the challenge lies in managing both surplus and deficit rainfall scenarios within a single cropping season (Garud et al., 2019) [4] . The integration of pigeonpea-based intercropping systems with INM and BBF land configuration offers a holistic approach to enhance crop productivity, improve soil health, and ensure resource-use efficiency under rainfed conditions.

Materials and Methods

A field experiment was conducted during the kharif seasons of 2023-24 and 2024-25 at the AICRP Experimental Farm on Dryland Agriculture, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani (Maharashtra), to evaluate the effect of pigeonpea-based intercropping systems and integrated nutrient management on physiological growth parameters of pigeonpea.

The experiment was laid out in a split-plot design with three replications, comprising four intercropping systems in main plots-pigeonpea + soybean, pigeonpea + pearl millet, pigeonpea + sesame, and pigeonpea + sorghum in a 1:4 row ratio and four integrated nutrient management practices in sub-plots, including F₁: 100% recommended dose of fertilizers (RDF); F₂: 75% RDF supplemented with 1.5 t FYM ha⁻¹ and 0.5 t vermicompost ha⁻¹ along with foliar application of NAA and KNO₃; F₃: 50% RDF combined with 3.0 t FYM ha⁻¹ and 1.5 t vermicompost ha⁻¹ along with foliar application of NAA and KNO₃; and F₄: control. Physiological parameters such as absolute growth rate for plant height and dry matter accumulation, and crop growth rate were recorded at different growth stages and analyzed statistically using ANOVA appropriate for the split-plot design.

Absolute growth rate for plant height

The Absolute Growth Rate (AGR) is the total gain in plant height by the plant within the specific time interval. Absolute growth rate for plant height is expressed as cm day -1 plant -1 and is calculated by the formula given by Richards (1969) [5] as follows.

Where, H 2 and H 1 are plant height (cm) at time T 2 and T 1 , respectively. The Absolute Growth Rate (AGR) is the total gain in dry matter by the plant within the specific time interval and expressed as g day -1 plant -1 for dry matter accumulation plant -1 Where, W 2 and W 1 are the dry weight (g) plant at time T 2 and T 2 , respectively.

The crop growth rate is commonly used for the determination of production efficiency of plant stand. CGR represents total dry matter productivity of the community per unit land area over a certain time span. CGR enables comparison to be made between stand communities of different types in different habitat (Watson, 1952) [7] . This is determined by using the following formula.

Where, W 2 = dry weight of plant at time T 2 (g plant -1 ) W 1 = dry weight of plant at time T 1 (g plant -1 ) p = spacing

Results and Discussion

Physiological growth dynamics

Growth functions are the measures of growth rates in different growth parameters of plant.

The data presented in the tables 1 and 2 indicate that the absolute growth rate of pigeonpea increased progressively from sowing up to 61-90 DAS, after which a declining trend was observed towards harvest.

Effect of pigeonpea based intercropping systems

Among the pigeonpea-based intercropping systems, pigeonpea + pearl millet (1:4) recorded comparatively higher AGR during the most active growth phase (61-90 DAS), followed by pigeonpea + sorghum (1:4), while lower values were observed under pigeonpea + soybean (1:4) and pigeonpea + sesame (1:4) at later growth stages.

Effect of integrated nutrient management practices

With respect to integrated nutrient management practices, application of 75% RDF supplemented with FYM, vermicompost and foliar sprays of NAA and KNO₃ resulted in the highest AGR across most growth stages, followed closely by the application of 100% RDF. Reduced fertilizer dose combined with higher organic inputs showed intermediate values, whereas the control treatment consistently recorded the lowest AGR throughout the crop growth period.

The absolute growth rate (AGR) of dry matter accumulation per plant at different growth stages under various intercropping systems and integrated nutrient management practices during kharif seasons of 2023-24 and 2024-25 is presented in Table 3 and 3.4, respectively. The mean AGR for dry matter increased from 0-30 DAS and attained maximum values during 61-90 DAS, followed by a declining trend from 91 DAS up to harvest during both the years.

Effect of pigeonpea-based intercropping systems

The pigeonpea based intercropping systems showed variation in AGR for dry matter at different growth stages during both years. Pigeonpea + Soybean (1:4) (I₁) recorded comparatively higher AGR values for dry matter during the peak growth period, followed by Pigeonpea + Sesame (1:4) (I₃) and Pigeonpea + Sorghum (1:4) (I₄). Lower AGR values for dry matter were observed under Pigeonpea + Pearl millet (1:4) (I₂) across most of the growth stages during both the years.

Effect of integrated nutrient management practices

The integrated nutrient management practices differed with respect to AGR for dry matter at various growth stages during both years. 75% RDF + 1.5 t FYM + 0.5 t vermicompost + NAA and KNO₃ spray (F₂) recorded the highest AGR values for dry matter, followed by 100% RDF (F₁) and 50% RDF + 3 t FYM + 1.5 t vermicompost + NAA and KNO₃ spray (F₃). The control treatment (F₄) recorded the lowest AGR values at all growth stages during both the years of study.

References

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