Gross primary production and ecosystem respiration of irrigated and rainfed maize-soybean cropping systems over 8 years

Andrew E. Suyker, Shashi B. Verma

Research output: Contribution to journalArticlepeer-review

106 Scopus citations


The objective of this study is to examine interannual variability of carbon dioxide exchange and relevant controlling factors in irrigated and rainfed maize-soybean agroecosystems. The mean annual gross primary production (GPP) of irrigated and rainfed maize was 1796±92gCm -2y -1 (±standard deviation) and 1536±74gCm -2y -1, respectively. Mean annual GPP of soybean (average of irrigated and rainfed crops) was about 56% that of maize. Light use efficiency of maize and soybean during clear sky conditions were 1.96±0.10 and 1.37±0.06gCMJ -1, respectively. A light use efficiency model, incorporating sensitivity to diffuse light, provided a reasonable simulation of daily GPP of maize and soybean (r 2=0.89-0.98 and 0.85-0.97, respectively). Simulated growing season GPP totals were within about 10% of the measured values. The green leaf area index (LAI) played a dominant role in explaining interannual variability of GPP in maize. For soybean, both LAI and PAR contributed to the interannual variability. Mean growing season ecosystem respiration (Re) totals were 1029±46gCm -2 for irrigated maize and 872±29gCm -2 for rainfed maize. The growing season Re total of soybean (average of irrigated and rainfed crops) was about 78% that of maize. A relationship, based on a reference soil respiration (Re 20), air temperature (T a), and LAI, simulated daily growing season Re reasonably well for maize and soybean (r 2=0.77-0.91 and 0.51-0.94, respectively). Modeled Re totals during the growing season were generally within 10% of the measured values. Variations in the LAI and Re 20 explained the majority of the interannual variability in growing season Re for maize. In addition to LAI and Re 20, T a also contributed to the soybean Re variability. Non growing season Re contributed 10-20% and 17-24% of annual Re in maize and soybean, respectively and was primarily controlled by air temperature and residue biomass (r 2∼81%). About 70% of maize GPP was lost in Re, resulting in the mean annual net ecosystem CO 2 production (NEP) of 552±73gCm -2y -1 for irrigated maize and 471±52gCm -2y -1 for rainfed maize. For soybean, however, most of the annual GPP was lost in Re resulting in a mean annual NEP of -57±43 and 10±52gCm -2y -1 for irrigated and rainfed soybean, respectively. In general, as compared to Re, GPP contributed more to explaining the departures (ΔNEP) of NEP from the 4-year mean for maize. Both GPP and Re contributed to the ΔNEP for soybean. Results on the net biome production (NBP) indicated that the irrigated maize-soybean rotation was initially a moderate source of carbon; however, the system appears to be approaching near C neutral recently. The rainfed maize-soybean rotation is approximately C neutral.

Original languageEnglish (US)
Pages (from-to)12-24
Number of pages13
JournalAgricultural and Forest Meteorology
StatePublished - Nov 15 2012
Externally publishedYes


  • Ecosystem respiration
  • Gross primary production
  • Light use efficiency
  • Maize
  • Net ecosystem production
  • Soybean

ASJC Scopus subject areas

  • Global and Planetary Change
  • Forestry
  • Agronomy and Crop Science
  • Atmospheric Science


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