Response of Dry Matter Accumulation and Yield Stability in Intercropped Maize to Biochar Application Under Nitrogen Reduction

In the arid irrigated areas of northwest China, monoculture cropping systems, high dependence on nitrogen fertilizer, and inadequate farmland protection have led to degraded soil quality and reduced farmland productivity, severely constraining crop yield improvement and sustainable production. This study integrated intercropping with leguminous crop, nitrogen reduction, and biochar application to investigate their synergistic effects on maize dry matter accumulation and distribution characteristics, maize yield, and yield stability, aiming to provide a theoretical basis and technical support for establishing a green and efficient sustainable maize production model in this region.

The experiment was conducted from 2022 to 2024 at the Oasis Agriculture Comprehensive Experimental Station of Gansu Agricultural University. A split-split-plot field experiment was employed, with the main plots assigned to cropping patterns (maize ǁ fresh-edible pea, IM; sole maize, SM), the subplots to nitrogen application levels (conventional rate N₁, 360 kg·hm^-2; reduced nitrogen by 30% N₂, 250 kg·hm^-2), and the sub-subplots to biochar treatments (application, C, 15 t·hm^-2; no application, B). Indicators including maize dry matter accumulation and distribution, grain yield, and yield stability were systematically measured.

Compared with monocropping, the intercropping pattern significantly increased maize grain yield, dry matter accumulation, and yield stability. Reducing nitrogen by 30% significantly decreased maize dry matter accumulation, maximum growth rate, ear dry matter allocation ratio, and grain yield, but biochar application effectively mitigated these negative effects. Biochar increased the maximum aboveground dry matter growth rate by 6.7%-33.7% for maize ǁ fresh-edible pea and by 9.4%-24.1% for sole maize, respectively. Under intercropping conditions, the treatment with 30% nitrogen reduction combined with biochar application (IMN₂C) showed no significant differences in grain yield, dry matter accumulation dynamics, and yield stability compared to the full nitrogen rate treatment (IMN₁C) and was significantly superior to other treatment combinations, and compared to the conventional nitrogen application without biochar in monocropped maize (SMN₁B), this treatment increased grain yield by 17.0%-19.2%. The underlying mechanism primarily involved biochar promoting maize root growth by increasing soil organic carbon and total nitrogen content, optimizing the root-to-shoot ratio, thereby ensuring efficient dry matter accumulation throughout the entire growth period. Particularly during the critical grain-filling stage, it maintained a high growth rate and promoted the preferential allocation of dry matter to the ears.

In the arid irrigated areas of northwest China, the integration of maize fresh-edible pea intercropping and biochar application, along with a 30% reduction in nitrogen fertilizer input, can effectively maintain maize yield and yield stability by improving soil fertility, promoting root development, and optimizing dry matter partitioning. This approach represents a feasible agronomic strategy for achieving synergistic reduction of chemical nitrogen fertilizer use and stable maize production in the region.