Impacts of tillage systems, nitrogen fertilizer rates and a legume green manure on light interception and yield of winter wheat

Abstract

Combining conservation tillage with legumes grown as a green manure is an increasingly popular practice for crop production in the U.S. Southern Great Plains. This study investigated interactions between system of tillage (no-till vs. conventional tillage) and source and amounts of nitrogen (N) fertilization (0, 45 and 90 kg N ha–1 yr–1 in inorganic N fertilizer, and cowpea as a green manure) on radiation use efficiency, and dry matter (DM) yield of winter wheat. The study was conducted at two sites during the 2016–2017 growing season of winter wheat. Fraction of intercepted photosynthetically active radiation (fPAR) was derived by measurements of canopy spectral reflectance taken at 1–2 weeks intervals as ratio vegetation index (RVI). Total cumulative intercepted fPAR (IPAR) during the cropping period was calculated as a product of half global radiation and fPAR. Radiation use efficiency (RUE) was calculated as the ratio of biomass yield and IPAR. At both sites, N treatments had stronger influences on crop growth than tillage systems. The RVI, IPAR and DM yield were generally higher under 90-N treatments followed by 45-N treatment. Responses of cowpea and control treatments were similar and the lowest. Radiation use efficiency was not influenced by tillage systems or N treatments.

Keywords

• light interception
• tillage
• nitrogen
• canopy reflectance
• radiation-use efficiency