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Nitrogen and solar radiation dynamics in soybean/maize systems
Abstract
The ability of legumes to fix atmospheric nitrogen makes them important components of sustainable cropping systems. Field studies were conducted to investigate (1) the residual nitrogen and yield benefits from different soybean densities to following maize and (2) the effect of row arrangement and nitrogen application rate on % photosynthetic active radiation (PAR) interception, productivity, nitrogen transfer and residual benefits from soybean/maize intercrops and sole crops. Eight soybean densities (14,000 to 544,000 plants ha$\sp{-1}),$ bare fallow and a maize plot were followed by maize in a rotation study. Five soybean/maize intercrop row arrangements and three sole crops were followed by maize in an intercropping study. The net positive N balance reached a maximum of 17 kg N ha$\sp{-1}$ and soybean depleted soil N at population densities below 20,000 plants ha$\sp{-1}.$ Maize grain yields were highest following bare fallow and soybean densities below 20,000 plants ha$\sp{-1},$ intermediate following higher soybean densities, and least in continuous maize. Nitrogen credits to maize (16 to 46 kg N ha$\sp{-1})$ calculated from Fertilizer N Replacement Value (FRV) overestimated the potential N contribution from soybeans. Yield increase of maize in rotation with soybeans may be attributed to N added to the soil from N$\sb2$ fixation, N sparing, and non-N rotation effects possibly related to increased water availability. Percent PAR intercepted by intercrops was greater (83 to 97%) in closer row arrangements of soybean and maize than 2rows soybean:2rows maize (77 to 94%), and increased (2 to 5%) by N application. Dry matter productivity of the intercrops was higher than sole crops, and was enhanced to a maximum increase of 38% over sole crops by close association of soybean and maize, N application and limited moisture availability. The maximum of 20% grain yield increase of intercrops over sole crops was not significant (p $<$ 0.05). There was evidence of N transfer in the alternate 1row soybean:1row maize arrangement which increased from 8 to 21 kg N ha$\sp{-1}$ with N application. Nitrogen uptake and maize grain yields were generally highest following sole soybean, intermediate following soybean/maize intercrops and least following sole maize.
Subject Area
Agronomy
Recommended Citation
Ennin, Stella Ama, "Nitrogen and solar radiation dynamics in soybean/maize systems" (1997). ETD collection for University of Nebraska-Lincoln. AAI9805502.
https://digitalcommons.unl.edu/dissertations/AAI9805502