Spatio-temporal dynamics of root traits regulate nutrient acquisition and yield of pigeonpea-wheat based system under organic and natural farming.

Root system development strongly influences nutrient acquisition, yield formation, and these processes are largely influenced by crop management strategies. Meagre information is available on functional traits of roots that regulate nutrient acquisition and productivity of pigeonpea under organic and natural farming systems in semi-arid regions. This study aimed to quantify the spatial and temporal dynamics of root morphological traits, nutrient acquisition and grain yield of pigeonpea under specific crop management strategies. A field experiment was initiated during 2021-22 under a pigeonpea-wheat system with seven treatments viz.; conventional farming (CF), natural farming (NF) and five compost rates (0, 6, 12, 18, and 24 t ha- 1). Root samples were collected at 45, 90, and 135 days after sowing (DAS) from two soil depths (0-15 and 15-30 cm) to assess the impact of different treatments on root functional traits, nutrient acquisition, and seed yield of pigeonpea in the year, 2024. The root growth and nutrient acquisition peaked at the flowering stage (90 DAS), subsequently declined during the pod filling stage (135 DAS). Compared with natural farming and conventional farming, compost (12 t ha- 1) increased root length density by 23.3 & 8.0%, root surface area by 23.0 & 17.6%, root volume by 22.7 & 20.9%, root fresh weight (RFW) by 22.7 & 15.0%, respectively, in the 0-15 cm soil layer at the flowering stage. The higher nutrient content (phosphorus and potassium) was noticed with the same treatment (0.35 and 0.98%, respectively), followed by compost (6 t ha- 1). The order of treatments in terms of nutrient contents were compost (12 t ha- 1)> compost (6 t ha- 1) > CF> compost (18 t ha- 1) > NF > compost (24 t ha- 1); in contrast, higher nitrogen content was observed in NF (3.96%) followed by compost (12 t ha- 1). Root morphological traits positively correlated (p < 0.001) with nutrient uptake, particularly for phosphorus and potassium, suggesting that improved root development enhanced nutrient acquisition from the soil and played a key role in yield formation. Seed yield ranged from 10.1 to 13.4 q ha⁻¹ and crop supplied with compost @ 12 t ha- 1 produced 16.5 and 19.2% higher yield than CF and NF, respectively. Regression analysis showed a linear relationship between grain yield and nutrients uptake across all crop growth stages. The seed yield was positively and strongly correlated to P uptake at 45 DAS (R² = 0.85, p < 0.001), followed by the flowering stage (R² = 0.83) and pod filling stage (R² = 0.75). Spatio-temporal variation in root traits strongly regulated nutrient acquisition and yield formation in pigeonpea. Optimized compost application (12 t ha- 1) enhanced root development and nutrient uptake, with root phosphorus accumulation emerged as the key driver of grain yield, underscoring its importance for sustainable pigeonpea production.