Nitrogen recovery efficiency for corn intercropped with palisade grass

ABSTRACT Intercropping corn and palisade grass is a technique to increase straw production, soil C contents, nutrient cycling and crop yield. However, concerns arise from nitrogen (N) uptake by the intercropping crop causing reduction in the yield of the corn. Our objective was to evaluate N recovery efficiency (NRE), and the N dynamics in the soil-plant system in corn intercropped with palisade grass. A field trial was carried out in Bahia, Brazil, evaluating two cropping systems: corn (monoculture) and corn intercropped with palisade grass sowed between rows on the same day as the corn crop, with four replicates in a completely randomized block design. Nitrogen (150 kg∙ha–1of 15N-urea) was applied at sowing to determine NRE, which means the amounts of N-fertilizer uptake in corn and palisade grass, the amounts of N-fertilizer in soil and the 15N-fertilizer balance. Neither the NRE (63.3% in monoculture and 57.2% in intercropping) nor corn grain yield (9,800 kg∙ha–1 in monoculture and 9,671 kg∙ha–1 in intercropping) was affected by intercropping, which accumulated only 2.1 kg∙ha–1 of N-fertilizer or 1.4% N rate. In addition, palisade grass yielded 2,265 kg∙ha–1 of dry matter. The balance indicated that 82.4% of N-fertilizer was recovered in the monoculture and 86.9% in the intercropping. Intercropping palisade grass does not affect grain yield or N corn nutrition and has the potential to increase straw production contributing to maintenance of no-till.

摘要 玉米与巴拉草（palisade grass）间作是一项可提升秸秆产量、土壤有机碳含量、养分循环及作物产量的种植技术。然而，间作作物对氮素（N）的吸收可能导致玉米产量下降，由此引发相关担忧。本研究旨在评估玉米与巴拉草间作体系中的氮素回收效率（N recovery efficiency, NRE）以及土-植系统内的氮素动态变化。试验于巴西巴伊亚州开展，设置两种种植体系：玉米单作，以及与玉米同期在行间播种的玉米-巴拉草间作，采用完全随机区组设计，设置四次重复。播种时施加150 kg·公顷⁻¹的15N标记尿素（15N-urea）以测定氮素回收效率，具体指标包括玉米与巴拉草的氮肥吸收量、土壤中的氮肥残留量以及15N肥料平衡情况。结果显示，间作并未对氮素回收效率（单作组为63.3%，间作组为57.2%）与玉米籽粒产量（单作组为9800 kg·公顷⁻¹，间作组为9671 kg·公顷⁻¹）产生显著影响；间作体系中的巴拉草仅累积了2.1 kg·公顷⁻¹的氮肥，占总施氮量的1.4%。此外，巴拉草的干物质产量达2265 kg·公顷⁻¹。肥料平衡分析表明，单作体系中82.4%的氮肥被回收利用，间作体系的回收比例则为86.9%。综上，玉米与巴拉草间作不会影响玉米籽粒产量与氮素营养，且具备提升秸秆产量的潜力，有助于维持免耕（no-till）栽培体系。