عنوان مقاله [English]
Evaluation of net primary productivity and carbon allocation to different organs of corn under nutrient management and tillage systems
Agriculture operations produce 10 to 20 percent of greenhouse gases. As a result of conventional operations of agriculture, greenhouse gases have been increased (Osborne et al., 2010). Therefor it is necessary to notice to carbon sequestration to reduce greenhouse gases emissions. In photosynthesis process, plants absorb CO2 and large amounts of organic carbon accumulate in their organs. Biochar is produced of pyrolysis of organic compounds. Biochar is an appropriate compound for improved of soil properties and carbon sequestration (Whitman and Lehmann, 2009; Smith et al., 2010). Conservation tillage has become an important technology in sustainable agriculture due to its benefits. So the aim of this study was to evaluate the effect of nutrient management and tillage systems on net primary production and carbon allocation to different organs of corn in Shahrood.
Material and methods
This study was conducted at the Shahrood University of Technology research farm. Experiment was done as split plot in randomized complete block design with three replications. Tillage systems with two levels (conventional tillage and minimum tillage) were as the main factor and nutrient management in seven levels including (control, chemical fertilizer, manure, biochar, chemical fertilizer + manure, chemical fertilizer + biochar, manure + biochar) were considered as sub plot. At the time of maturity of corn, was sampled from its aboveground and belowground biomasses. Carbon content of shoot, seed and root was considered almost 45 percent of yield of each of these biomasses and carbon in root exudates almost 65 percent of carbon in the root. Statistical analysis of the data was performed using SAS program. Comparison of means was conducted with LSD test at the 5% level.
Results and discussion
Effect of nutrient management was significant on belowground and aboveground biomasses, total weight and net primary productivity. Maximum and minimum of shoot, seed, total weight and aboveground net primary productivity were obtained in chemical fertilizer and control respectively. Nitrogen plays a key role in several physiological crop processes. As a result of increasing N doses, the photosynthetic activity, leaf area index (LAI) and leaf area density (LAD) increase. Maximum and minimum of root weight and belowground net primary productivity were obtained in chemical fertilizer + manure and control respectively. Manure and biochar increased root weight 56/03 and 54/31 percent compared to control respectively that had no significant different to chemical fertilizer. Manure increased root growth, possibly through improved physical properties and increased nutrient and water availability. Manure decreases soil compatibility with increasing of stability of soil structure and soil resilient. Impact of adding manure on improving of root length density has been reported by Mosaddeghi et al. (2009). The increased maize yield in biochar amended soil could be attributed to increased nutrient availability (Chan et al. 2008; Zhang et al. 2010) and to improved soil physical properties indicated by decreased soil bulk density.
The results showed that nutrient management had significant effect on belowground and aboveground biomasses, total weight, below and aboveground net primary productivity and carbon allocated to different organs of corn. Maximum and minimum of belowground and aboveground net primary productivity was obtained in chemical fertilizer, manure+ chemical fertilizer and control respectively. Manure and biochar increased belowground net primary productivity 54/91 and 53/21 percent compared to control respectively that had no significant different to chemical fertilizer. Tillage systems had no significant effect on measured traits. The results showed that with application reduced tillage and manure and biochar can increase belowground net primary production and carbon allocation to belowground organs and by adding root residues to the soil can retain roots carbon and prevent its release into the atmosphere. Therefore with reduction of CO2 amount in atmosphere, climate change and global warming be reduced.