Optimizing Microclimate for Maize–Mushroom Intercropping Under Semi-Arid Conditions: A Climate-Smart Farming Approach ^†

Abstract

Agriculture in semi-arid regions faces increasing challenges from temperature extremes and moisture stress, necessitating climate-smart and resource-efficient production systems. This study examined maize–mushroom intercropping as a climate-smart strategy for semi-arid regions. Field experiments conducted at Tamil Nadu Agricultural University evaluated four maize planting geometries, with and without mulch, in 2022. Results showed that close-maize spacing (45 × 25 cm) with mulch moderated temperature, increased humidity, and improved mushroom yield and biological efficiency. The treatment achieved a land equivalent ratio above one, indicating superior land use efficiency. Optimal microclimatic conditions (26–33 °C; 80–98% RH) enhanced paddy straw mushroom growth, demonstrating that simple field-level modifications can stabilize microclimate and promote resilient farming in semi-arid ecosystems.

1. Introduction

Agriculture continues to anchor rural livelihoods and food security in India, contributing around 16% of national GDP and employing nearly 46.1% of the workforce [1]. Yet, semi-arid regions across peninsular India remain highly vulnerable to climate variability, characterized by erratic monsoon onset, rising temperature extremes, and persistent soil moisture stress. The Intergovernmental Panel on Climate Change [2] projects a 1.2–1.5 °C increase in mean surface temperatures and a 25–40% decline in soil moisture across South Asian drylands by 2050, posing serious threats to smallholder productivity.

In this context, climate-smart agricultural strategies that enhance resilience, resource efficiency, and carbon neutrality are indispensable for sustainable food production. Ecological intensification, which seeks to increase output per unit resource through ecosystem-based approaches, has emerged as a central tenet of climate-smart agriculture [3]. Within this paradigm, intercropping represents a biologically synergistic practice that enhances land productivity and stabilizes the microclimate. By combining crops with contrasting canopy structures and rooting depths, intercropping improves light interception, moisture retention, and soil biological activity [4].

Maize (Zea mays L.), often called the “queen of cereals,” is particularly suited to such systems due to its C₄ photosynthetic efficiency, rapid growth, and resilience to intermittent water stress. Its spatial flexibility and open canopy structure allow integration with compatible intercrops without yield penalties. Meta-analyses over the past five years indicate that maize-based intercropping systems achieve Land Equivalent Ratios (LER) exceeding 1.2–1.4, underscoring their potential to sustain yield gains under variable climates [5,6].

Among possible intercrops, paddy straw mushroom (PSM; Volvariella volvacea) offers a high-value, short-duration complement to cereal systems. As a “warm mushroom” thriving at 28–35 °C and 80–95% relative humidity, V. volvacea aligns naturally with tropical climates and can be harvested within 20–25 days. It utilizes locally available residues such as paddy straw, maize stalks, and sugarcane trash, thus embodying principles of circular bioeconomy and resource recycling. Beyond income diversification, its integration between maize rows functions as a living mulch, reducing surface evaporation, moderating soil temperature, and suppressing weeds.

Earlier studies demonstrated that shaded or semi-controlled environments can sustain optimal PSM yields without costly infrastructure. Thiribhuvanamala et al. [7] successfully cultivated the mushroom under outdoor maize–banana intercrops, maintaining 35–37 °C and 80–85% relative humidity with biological efficiency up to 20%. Similarly, ref. [8] found that cultivation beneath tropical tree canopies achieved optimal productivity between 28 and 30 °C and 85–90% humidity, conditions replicable under crop canopies with dense foliage. These findings indicate that controlled microclimates in intercropping systems can substitute for energy-intensive polyhouses, allowing sustainable production through natural shading and mulching.

Nevertheless, PSM remains highly sensitive to microclimatic fluctuations. While polyhouse cultivation offers environmental control, it remains economically unviable for smallholders. Thus, optimizing field-level microclimates through crop geometry and organic mulching presents a practical, low-cost alternative for semi-arid conditions. Microclimate regulation by air temperature, relative humidity, soil moisture, and canopy shade directly influences the biological efficiency and yield of intercrops. Recent advances in agrometeorological monitoring have shown that subtle field-level adjustments can buffer temperature extremes by 3–5 °C and sustain relative humidity above 80% under high evaporative demand [9,10,11].

Tamil Nadu western agroclimatic zone, particularly Coimbatore, represents a semi-arid environment with annual rainfall of 700–750 mm and potential evapotranspiration exceeding 1800 mm. These conditions provide an ideal setting to evaluate how maize canopy modification, through varied row spacings and mulching, can establish a favorable microclimate for paddy straw mushroom cultivation. Although earlier experiments at Tamil Nadu Agricultural University demonstrated the feasibility of maize–mushroom intercropping, quantitative assessments of microclimate–yield relationships remain limited. In particular, there is inadequate documentation of threshold parameters, seasonal responses, and comparative performance of different planting geometries under semi-arid regimes.

Therefore, the present study was conducted at the Agro Climate Research Centre, TNAU, during the summer and kharif seasons of 2022, to evaluate the effects of maize–mushroom intercropping under different row spacings and mulching practices on microclimate, yield, and resource-use efficiency. By integrating agrometeorological principles with ecological intensification, this research aims to demonstrate that microclimate management through field-level design can enhance productivity, stability, and resilience in vulnerable dryland ecosystems.

The findings from this study have wider implications for advancing climate-smart and ecologically intensive farming systems in semi-arid regions. By demonstrating that strategic manipulation of maize canopy geometry and the use of organic mulch can create favorable microclimates for PSM under open-field conditions, this research provides a scalable, low-cost model for integrating high-value fungi into cereal-based systems. Such integration promotes efficient resource recycling, diversifies farm income, and enhances resilience to climatic variability without reliance on energy-intensive infrastructure in dryland agroecosystems.

2. Materials and Methods

2.1. Experimental Site

The study was conducted in field no. 36 of the Eastern Block, Central Farm Unit, Tamil Nadu Agricultural University, Coimbatore. The experimental field is geographically situated at the latitude of 11°01′ N, longitude of 76°93′ E, and altitude of 426.7 m MSL.

2.2. Experiment Design and Treatment Details

A randomized block design (RBD) with three replications and eight treatments was used, along with a polyhouse control.

2.3. Layout and Implementation of Maize–Mushroom Intercropping

The field experiment followed a randomized block design (RBD) with three replications and nine treatments (

Table 1. Details of experimental treatments.

Treatment Details
T1	60 cm × 25 cm wide-row spacing
T2	45 cm × 25 cm close-row spacing
T3	45/75 cm × 25 cm wide-paired row spacing
T4	30/60 cm × 25 cm close-paired row spacing
T5	T1 + Mulching
T6	T2 + Mulching
T7	T3 + Mulching
T8	T4 + Mulching
T9	Polyhouse

) to evaluate the effects of maize spacing and mulching on the microclimate and productivity of maize–mushroom intercropping. Mushroom beds were introduced between two rows of maize, and each bed was covered with a semi-transparent blue polyethylene sheet to conserve moisture, maintain warmth, and prevent contamination from external particles. The polyethylene cover was retained throughout the cropping cycle to sustain a stable microenvironment (Figure 1).

Each bed received 500 g of Volvariella volvacea spawn, uniformly distributed across the substrate. Following inoculation, beds were incubated for 10–12 days until pinhead formation, after which the covers were partially opened to facilitate aeration and fruiting for an additional 25–30 days. The developmental stages of V. volvacea (pinhead, button, egg, elongation, and maturity) are shown in Figure 2.

The intercropping layout was designed to replicate microclimatic conditions favorable for paddy straw mushroom growth, characterized by temperatures of 28–33 °C and relative humidity of 80–90%, as reported in previous agroforestry-based studies [8]. The maize canopy and organic mulch were used to regulate soil temperature and humidity, thereby recreating optimal conditions for mushroom development under semi-arid field environments.

2.4. Microclimate Monitoring

The microclimate of the maize–mushroom intercrop system was evaluated under semi-arid field conditions through the evaluation of the microclimate in relation to the various maize geometries and mulching treatments as they relate to the optimal growing environment for Volvariella volvacea. Air temperature, relative humidity, soil temperature, bed moisture, and light intensity were measured continuously with digital sensor instrumentation placed both inside the maize canopy and 5 cm above the mushroom beds (representing the microclimate of Volvariella volvacea). To maintain data integrity, all of the data loggers were synchronized and protected against direct solar heat. All of the recorded data were checked periodically using the meteorological observation data available at the Agro Climate Research Centre, TNAU, to ensure that the data collected were accurate in both indoor and outdoor environments under semi-arid conditions.

The objective of this research is to investigate and determine what combinations of maize crop canopy and mulching methods will provide the optimal microclimate for the growth and development of PSM while providing an optimal microclimate temperature (26–33 °C) and optimal moisture (80–98%) within the maize crop-soil interface. Using the framework established by [8], who found that V. volvacea production in tropical agroforestry systems is heavily dependent on bed temperature (28–33 °C) and humidity (85–90%), this research will explore whether maize planting density and organic mulch can create the same environmental conditions under semi-arid conditions. Thus, the relationship among maize canopy shading, soil cover, and ambient weather conditions will be examined as the primary mechanism through which microclimate conditions are optimized and as the foundation of this climate-smart strategy for intercropping.

$$\mathrm{Biological} \mathrm{Efficiency} (\mathrm{BE})={\displaystyle \frac{\mathrm{Total} \mathrm{weight} \left(\mathrm{kg}\right) \mathrm{of} \mathrm{harvested} \mathrm{fresh} \mathrm{mushrooms}}{\mathrm{Total} \mathrm{dry} \mathrm{weight} \left(\mathrm{kg}\right) \mathrm{of} \mathrm{substrate} \mathrm{used}}}\times \mathrm{100}$$

This metric indicated the conversion efficiency of the substrate into mushroom biomass, serving as a key index of system productivity and resource use.

Land Equivalent Ratio (LER)

$$\mathrm{LER}={\displaystyle \frac{\mathrm{Yield} \mathrm{of} \mathrm{maize} \mathrm{in} \mathrm{intercrop}}{\mathrm{Yield} \mathrm{of} \mathrm{maize} \mathrm{in} \mathrm{a} \mathrm{sole} \mathrm{crop}}}+{\displaystyle \frac{\mathrm{Yield} \mathrm{of} \mathrm{mushroom} \mathrm{in} \mathrm{intercrop}}{\mathrm{Yield} \mathrm{of} \mathrm{mushroom} \mathrm{in} \mathrm{a} \mathrm{sole} \mathrm{crop}}}$$

(1)

where yield of maize in intercrop and yield of mushroom in intercrop denote yields in intercropping, and yield of maize in sole crop and yield of mushroom in sole crop are corresponding monocrop yields. An LER > 1 indicates a yield advantage due to complementary resource utilization, while LER = 1 implies no advantage [12].

2.5. Statistical Analysis

All experimental data were statistically analyzed using the Analysis of Variance (ANOVA) technique appropriate for a Randomized Block Design (RBD) with three replications, as outlined by [13]. The significance of treatment effects was tested at the 5% probability level (p < 0.05). For each parameter (air temperature, relative humidity, mushroom yield, and BE%), the Standard Error of Difference (SEd) and Critical Difference (CD) at the 5% level of significance were computed to assess treatment variability and to determine statistically significant differences among treatment means.

3. Results

3.1. Effect of Microclimate Modification on Mushroom Growth and Yield

The maize planting density and mulching were significant in creating microclimatic conditions within the maize–mushroom intercrop (

Table 2. Microclimatic variables in different treatments during summer and kharif.

Treatment		Temperature (°C)		Relative Humidity (%)
		Summer	Kharif	Summer	Kharif
T1	Wide row 60 × 25 cm	29.8	25.8	75.3	80.9
T2	Close row 45 × 25 cm	29.9	25.7	77.2	81.6
T3	Wide-paired row 45/75 × 25 cm	29.9	26.1	73.6	79.6
T4	Close-paired row 30/60 × 25 cm	29.6	25.7	76.1	81.6
T5	T1 + Mulching	29.5	25.5	75.9	80.7
T6	T2 + Mulching	29.2	25.8	78.5	81.3
T7	T3 + Mulching	29.4	25.4	74.5	79.4
T8	T4 + Mulching	29.2	25.3	77.4	81
T9	Polyhouse	33.8	29.6	87.1	84.8
	Mean	30.0	26.1	77.3	81.2
	SEd	0.3	0.2	0.6	0.5
	CD (0.05)	0.6	0.4	1.3	1.1

). During the summer season, temperatures across treatments ranged from 29.2 to 33.8 °C, while relative humidity (RH) varied between 73.6% and 87.1%. In the kharif season, temperatures ranged from 25.3 to 29.6 °C, and RH was between 79.4% and 84.8%. Among the field treatments, the close-maize spacing with mulch (T₆) maintained the most favorable environment, with mean temperatures of 29.2 °C (summer) and 25.8 °C (kharif), and corresponding RH values of 78.5% and 81.3%, respectively. The polyhouse control (T₉) recorded the highest humidity (87.1–84.8%) and temperature stability. However, field-based treatment (T₆) produced almost ideal growing conditions for mushrooms in the field.

3.2. Mushroom Yield and Biological Efficiency

The yields in both seasons range from 256 g/bed for T₃ to 589 g/bed for T₆. The biological efficiencies (BE) range from 8.5% to 22.7%. The close spacing with mulch (T₆) resulted in the greatest yield for both seasons (580 g bed-1 in the summer; 589 g bed-1 in the kharif) and also resulted in the greatest BE (19.3%, 19.6%). The polyhouse control (T₉) was the treatment that produced the greatest yield for each respective season (summer: 603 g bed⁻¹; kharif: 681 g bed⁻¹), and it also produced the greatest BE (20.1–22.7%) (

Table 3. Mushroom yield and biological efficiency (BE %) during summer and kharif.

Treatment	Yield (g Bed−1)		BE (%)
	Summer	Kharif	Summer	Kharif
T1	468	510	15.6	17.0
T2	519	563	17.3	18.8
T3	256	348	8.5	11.6
T4	503	525	16.8	17.5
T5	537	544	17.9	18.1
T6	580	589	19.3	19.6
T7	323	381	10.8	12.7
T8	546	553	18.3	19.4
T9	603	681	20.1	22.7
Mean	482	522	16.1	17.4
SEd	27	27	0.9	0.9
CD (0.05)	57	58	1.9	1.9

). However, its feasibility as an economically viable option for small-scale production is limited. In general, all mulched treatments (T₅–T₈) were greater than their respective non-mulched treatments, indicating the importance of retaining soil moisture and providing some level of canopy shading to improve mushroom growth.

3.3. Land Equivalent Ratio (LER) and System Efficiency

All intercropping treatments recorded LER values greater than 1, confirming a yield advantage over sole cropping (Figure 3). LER ranged from 1.45 to 1.97 across treatments and seasons. The highest LER was obtained under T₆ during both summer and kharif seasons (1.97). The lowest LER (1.45) was observed in T₃, indicating less effective spatial complementarity under wide-paired rows without mulch. System productivity increased by 15–20% under optimized microclimate conditions (T₆) compared to non-optimized treatments.

4. Discussion

4.1. Microclimate Regulation Through Maize Canopy and Mulching

The present study demonstrated that modifying maize canopy geometry and applying organic mulch can significantly improve microclimatic conditions for mushroom cultivation under semi-arid field conditions. Close-maize spacing (45 × 25 cm) with mulch (T₆) reduced mean air temperature by 0.6 °C and increased relative humidity by 3% compared with wide spacing without mulch (T₁). These findings align with [7], who reported that intercropping paddy straw mushroom with maize and banana effectively utilized the natural microclimate, maintaining temperatures of 29–30 °C and bed relative humidity of 84–86.5%, and achieved biological efficiency up to 19–20% under outdoor conditions. The enhanced relative humidity under T₆ closely matched the optimal range of 80% RH reported by [8] for Volvariella volvacea cultivation beneath tropical forest canopies. Their work emphasized that a stable microclimate, especially with moderated daytime temperature and sustained humidity, is the most critical determinant of fruiting success in V. volvacea. Thus, maize canopy shading and mulching acted as biophysical regulators, replicating controlled-environment conditions in an open-field system, confirming that microclimate optimization is achievable through simple agronomic modifications.

4.2. Influence of Microclimate on Mushroom Yield and Biological Efficiency

The improved thermal and moisture regimes in the T₆ treatment resulted in higher mushroom yield (580–589 g bed⁻¹) and biological efficiency (19.3–19.6%) compared with unmulched or wider spacing systems. These yield levels are comparable to those obtained under low-cost shade structures reported by [7] and within the physiological thresholds outlined by [8] (28–30 °C, 85–90% RH). The strong positive correlation between relative humidity and biological efficiency (r = 0.88*) further confirms the direct influence of microclimate stabilization on fungal metabolism and substrate utilization efficiency. Mulching contributed additional benefits by conserving bed moisture and suppressing soil temperature fluctuations, consistent with earlier findings in semi-arid agrosystems where organic mulches improved soil thermal conductivity [14].

4.3. Land Equivalent Ratio and System Productivity

The Land Equivalent Ratio (LER) values (>1 in all treatments) demonstrate a clear yield advantage of intercropping over monocropping. The highest LER (1.93–1.96) obtained under T₆ highlights the synergistic use of light, moisture, and space by maize and mushrooms. Similar yield advantages and improved resource access have been observed in cereal–legume systems, where maize–cowpea intercropping enhanced LER and nutrient use compared with sole cropping [15]. In addition, maize–soybean strip intercropping has been shown to increase water use efficiency and productivity through improved soil water capture and complementary resource use [16]. The present results confirm that biological intensification through spatial arrangement and organic residue use can substantially increase system productivity by 15–25% under semi-arid conditions.

4.4. Implications for Climate-Smart Farming

This study demonstrates a scalable model of climate-smart intensification, showing that simple field-level adjustments can replicate the microclimatic benefits of controlled environments. The maize–mushroom intercropping system offers a low-cost pathway to enhance resource efficiency, resilience, and income diversification for smallholders in semi-arid regions. Its principles can be extended to similar drylands across Africa, Southeast Asia, and Latin America, where heat and water stress constrain diversification. By integrating short-duration fungi into cereal-based systems, farmers can recycle residues, reduce emissions, and strengthen climate adaptation in alignment with Sustainable Development Goals (SDG 2 and 13).

5. Conclusions

Optimizing maize canopy geometry and applying organic mulch effectively enhanced the microclimate for paddy straw mushroom cultivation under semi-arid conditions. Close-maize spacing (45 × 25 cm) with mulch treatment created a stable environment with moderate temperatures and high humidity, improved mushroom yield, and biological efficiency. The system achieved higher land use efficiency without reducing maize productivity, demonstrating strong compatibility between the two components. Overall, the maize–mushroom intercropping provides a practical, climate-smart, and resource-efficient approach to strengthen smallholder resilience in semi-arid farming systems.