Overcoming competition from intercropped forages on upland rice with optimized nitrogen input to food production in tropical region

Authors: CRUSCIOL, CARLOS - Sao Paulo State University (UNESP); PORTUGAL, JOSE - Sao Paulo State University (UNESP); MOMESSO, LETUSA - Sao Paulo State University (UNESP); BOSSOLANI, JOAO - Sao Paulo State University (UNESP); PARIZ, CRISTIANO - Sao Paulo State University (UNESP); CASTILHOS, ANDRE - Sao Paulo State University (UNESP); COSTA, NIDIA - Sao Paulo State University (UNESP); COSTA, CLAUDIO - Sao Paulo State University (UNESP); COSTA, CINIRO - Sao Paulo State University (UNESP); Franzluebbers, Alan; CANTARELLA, HEITOR - Sao Paulo State University (UNESP)

Submitted to: Frontiers in Sustainable Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2020
Publication Date: 9/3/2020
Citation: Crusciol, C.A., Portugal, J.R., Momesso, L., Bossolani, J.W., Pariz, C.M., Castilhos, A.M., Costa, N.R., Costa, C.H., Costa, C., Franzluebbers, A.J., Cantarella, H. 2020. Overcoming competition from intercropped forages on upland rice with optimized nitrogen input to food production in tropical region. Frontiers in Sustainable Food Systems. 4, Article 129.

Interpretive Summary: Cropping system diversification is needed to pursue greater productivity, but also to overcome threats to ecological stability. Intercropping of forages with cereal grains has potential to diversity agricultural operations and close nutrient cycling to reduce losses of nutrients to the environment. A scientist with USDA Agricultural Research Service in Raleigh NC collaborated with a team of investigators from Sao Paulo State University in Brazil to determine rice production with intercropping of tropical forage grasses as a source of forage for cattle consumption that would be ready for grazing during the winter dry season after rice grain harvest. Different nitrogen fertilization rates were applied to test if greater nitrogen availability was needed to overcome the competitive effects of the intercropped forage on rice grain yield, but that might also be needed for optimizing forage production. Greater nitrogen fertilizer inputs did lead to greater rice grain yield and to greater subsequent forage production. Intercropping systems were effective at increasing productivity and efficiently utilizing applied nitrogen more effectively. This research demonstrated the value of enhancing cropping systems diversity on agricultural productivity and points to potentially greater sustainability, by producing both cereal grain and livestock forage on the same land during the course of the year. This research will help farmers, extension specialists, and scientists to further refine cropping systems for greater sustainability.

Technical 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 need 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). Intercropped grasses were sown between upland rice rows 30 days after rice emergence. On average, intercropping of rice with palisadegrass or guineagrass reduced rice shoot dry matter and grain yield by 11% and milled rice productivity by 10% compared with monocropped rice. Agronomic characteristics of 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 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 application resulted in the greatest land equivalent ratio (1.96 and 1.55, respectively). Relative N yield was greatest at 120 kg N/ha (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.