Intercropping strategies for improving phosphorus availability and biomass yield

Overview

This research explores intercropping strategies that pair oat with legume species (lupin or alfalfa) in Andisol soils to improve phosphorus (P) availability and biomass yield. The core hypothesis is that oat/legume intercropping systems stimulate greater soil microbiological activity compared to oat monoculture, driven by active rhizodeposition in the presence of the legume. As a result, oat plants gain improved access to less available forms of soil P, leading to increased biomass and forage yield. A key benefit is the potential to decrease dependence on external P fertilizer inputs, offering both economic and environmental advantages for forage production systems.

Technical specifications

Cropping systems evaluated:

• Oat monoculture (control system)
• Oat/lupin intercropping (row intercropping 1:1)
• Oat/alfalfa intercropping (row intercropping 1:1)
• Lupin monoculture and alfalfa monoculture (reference treatments)

Key technical details:

• Legume species selected for complementary root traits: lupin develops root clusters for P mobilization; alfalfa associates with arbuscular mycorrhizal fungi (AMF)
• Rhizobium sp. inoculation applied to legume seeds at 1.0 x 10⁹ colony forming units mL⁻¹ before sowing to ensure effective nodulation
• Seed doses: 220 kg ha⁻¹ for oat; 120 kg ha⁻¹ for lupin and alfalfa
• Row spacing: 20 cm in monocultures; 40 cm in intercropping systems with alternate rows
• Fertilization treatments include triple superphosphate (220 kg ha⁻¹), potassium muriate (220 kg ha⁻¹), and urea (103 kg ha⁻¹), with and without P fertilizer application
• Measurements include soil chemical properties, basal soil respiration, enzyme activities, root morphological properties, and biomass yield for forage production

Technology readiness level

This is an active field research program at the early validation stage. The study is being conducted at the INIA Experimental Station Santa Rosa in south-central Chile's Mediterranean climate region, under irrigated conditions. The experimental design uses a factorial arrangement with two factors (cropping system and P fertilizer addition) and three replicates per treatment. The research is generating empirical data on soil biological activity, root morphology, and biomass productivity across the different cropping systems. Results will inform recommendations for sustainable forage production practices that reduce reliance on external phosphorus inputs.