Abstract
Intercropping forage grasses with upland rice is an alternative cropping system to improve agroecosystem diversification and could potentially enhance sustainability in tropical regions. However, nitrogen (N) immobilization and nutrient competition between rice and forage grasses could reduce rice grain yield and decrease overall productivity. Therefore, fertilizer N requirements of upland rice intercropped with forage grasses needs to be better defined. Field experiments were carried out during three growing seasons on a Typic Haplorthox soil in Sao Paulo state of Brazil. The experimental design was a randomized block design with a 3 × 4 factorial scheme with four replications. Treatments were cropping system [monocropped rice (Oryza sativa L.), rice intercropped with palisadegrass (Urochloa brizantha), and rice intercropped with guineagrass (Megathyrsus maximus) and sidedress N application rate (0, 40, 80, and 120 kg N ha-1). Intercropped grasses were sown between upland rice rows 30 days after rice emergence. On average, intercropping of rice with palisadegrass or guineagrass decreased rice shoot dry matter and grain yield by 11% and milled rice productivity by 10% compared with monocropped rice. Grain yield, grain protein, and milled productivity of rice increased as N application rate increased. Forage dry matter production (first and second cut) and crude protein (second cut) were greatest in the rice + palisadegrass intercropping system. Production of both forage grasses increased with up to 80 kg N ha-1 in the first cut and increased linearly with N in the second cut. Intercropping of rice with palisadegrass or guineagrass with 80 kg N ha-1 application resulted in the greatest land equivalent ratio (1.96 and 1.55, respectively). Relative N yield was greatest at 120 kg N ha-1 (220 and 173%, respectively). Although rice monocropping had greatest grain yield, intercropping systems with forage grasses were more favorable from both economic and environmental perspectives by enhancing plant diversification, nutrient cycling with forage grasses, land use production per unit area, and profitability throughout the year.
Highlights
Rice (Oryza sativa L.) is a staple food consumed by more than half of the world’s population (Emerick and Ronald, 2019) and one of the three most important cereal crops globally (Africa Rice Center - AfricaRice, 2019; Yadav et al, 2019)
The three cropping systems were: monocropped rice, rice intercropped with palisadegrass, and rice intercropped with guineagrass (Supplementary Figure 2)
Monocropped rice had similar N concentration as rice intercropped with palisadegrass and greater leaf P and K concentrations as with rice in the intercropping systems (Supplementary Table 2); N and P concentrations were lowest in rice intercropped with guineagrass
Summary
Rice (Oryza sativa L.) is a staple food consumed by more than half of the world’s population (Emerick and Ronald, 2019) and one of the three most important cereal crops globally (Africa Rice Center - AfricaRice, 2019; Yadav et al, 2019). The Cerrado of Brazil is the world’s largest producer of upland rice (Silva et al, 2020), a region where soils are acidic and of low fertility (Allen et al, 2007). Cropping systems based on conservation management with crop rotation, intercropping, integrated crop-livestock system (ICLS), and no-tillage system (NTS) are recommended to reduce soil degradation. These systems provide great efficiency in preserving natural resources and sustaining high agricultural production in tropical regions (Borghi et al, 2014; Crusciol et al, 2015; Moraes et al, 2019)
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