Carbon Footprint In Maize Cropland Under Different Plastic Film Mulching Patterns And Irrigation Regimes

Agricultural activities as a major source of greenhouse gases are making global warming issues more and moreseriously and causing a series of environmental problems, the establishment for the high-yield and lowe-carbon cropmanagement techniques are lack of theoretical basises. Based on the Thinking of Carbon Footprint, and the maizeas a typical crop in arid areas was selected as the tested material, through the field experiment, the whole carbonemission processes in maize land system within its growth periods were analyzed from a perspective of Life CycleAssessment in this study, and the effect of some agronomic practices: plastic film mulching rates (The rate of landsurface exposed was30%), planting patterns (Flat and ridge) and irrigation levels (Low, medium and high irrigationlevels) on the carbon footprint in maize land system were investigated. So as to provide the theoretical and practicalbasises for the establishment of high yield and low carbon maize production technical system in oasis agriculturalareas. The main resuls as follows:1. The CO2emission rates for all of the treatments in this study weren`t less than0.16μmolCO2·m-2·s-1in thewhole maize growth seasons. The CO2emission amounts were significantly affected by the mulching rates, plantingpatterns and irrigation levels, and the interaction of them on the CO2emission amounts was significant, too.Compered to the ridge treatments, the soil CO2emission rates in flat ones were increased by11.25%. The CO2emission rates could be enhanced by the complete mulch flat measures before the maize bell stage. After theirrigation gradients was made in field in maize bell stage, the irrigation amount became a major factor to the soilCO2emissions. Compared to the flat treatments, the CO2emission amounts in the ridge ones was decreased by9.16%. The total CO2emissions for C2was8274.42kg·hm-2, which was the highest in all, and the HR3was lowest,reaching5653.10kg·hm-2. Thus the treatment of HR3could be seemed as the optimal measure to decrease CO2emission amounts in maize growth seasons.After the irrigation gradients was made in field in maize bell stage, the irrigation amount became a dominatefactor to the soil N2O emission rate. The N2O emission amounts in maize growth seasons were significantly affectedby the mulching rates, planting patterns and irrigation levels. Before the maize bell stage, the half mulch plattreatments made the maize land system a library for absorbing N2O. Otherwise, the complete mulch ones had theopposite results; The measure of low and high irrigation level could decreased the N2O emission amounts in maizegrowth seasons. The N2O absorption amount in H2reached78.64kg·hm-2during the maize growth seasons, whichwas the effective library for N2O. There was a significant positive correlation (r=0.822, p=0.045) between theN2O and CO2emission amount in flat mushing areas. These showed that measures taken in H2could be seemed as the optimal measure to decrease the N2O emission amounts in maize growth seasons. The flat-mulching measureprovided a specific localized emission environment, which was different from the others.2. The planting patterns had a significant effect on the maize economic yield (Pplanting=0.007). Compared to theridge treatments, the economic yield of the flat ones were increased by2.06%~19.04%. At the same irrigation level,the flat treatments were19.04%,2.06%,5.00%and4.93%,11.02%,8.06%higher than the ridge ones in half andcompletely mulching measures. The carbon content of the maize organs aboveground in maize maturity were:spike> stem> sheath> leaf. The carbon content ratio of stem in maize maturity was significantly by the irrigationlevels. The mulching rate was the dominant factor to the carbon content ratio of leaf in maize maturity (P=0.002),and the carbon content ratio in sheath was significantly affected by the planting patterns (P=0.003). However, thedifferent irrigation levels had different significant effects on the carbon content ratio of spike. Compared to the ridgetreatments, the carbon content ratio of roots in flat ones were increased by5.03%.The CO2eq (Carbon equivalents represented by CO2eq) amounts for the maize organs aboveground weresignificantly affected by mulch rates and planting patterns, except to the irrigation levels. The CO2eq amount madeby the maize plants was81.92%in the total CO2eq of the maize land system, which was an effective library forcarbon. The CO2eq amounts of0-120cm soil roots were significantly affected by the mulching rates, plantingpatterns and irrigation levels (Pmulch rates=0.000, Pplanting=0.000, Pirrigation=0.000). Compared to the lowe and middleirrigation levels, the CO2eq amounts caused by the pump using the electricity energy in high ones were increasedby38.99%and16.24%. The CO2eq amounts in maize land system were significantly affected by the mulchingrates,planting patterns and irrigation levels (Pmulch×planting×irrigation=0.002). The CO2eq amounts of C2was the highestin all and reached108864.74kg·hm-2, while the treatment of H2was54825.72kg·hm-2, lowest. In various organs ofmaize in maturity stage, the average carbon content rates in spike (43.57%) and stem (43.99%) were close, both ofwhich were significantly higher than that of sheath (42.05%), leaves (40.55%) and root (40.05%). From all of above,we could know that the spike and stem were a main library of carbon storage in maize maturity stage. Comparedto the ridge treatments, the flat ones could effectively increase the carbon content rate of roots in0-120cm soil depth;Under the condition of flat and middle irrigation level, and combining the completely mulching measure, the highestCO2eq amount in maize growth seasons could be gotten, and combining the the half one, the lowest CO2eq amountin maize growth seasons could be gotten, which was the best combination for us.3. The carbon footprint in maize land system were significantly affected by the mulching rates and plantingpatterns in maize growth seasons. Otherwise, there were no significant difference in each of treatments under thecondition of ridge patterns. The irrigation levels were not the main factor for the carbon footprint in maize land system (Pmulch=0.000，Pplanting=0.009), and the interaction effects of the three main factors on the the carbonfootprint in maize land system was significant (Pmulch×planting×irrigation=0.025). The carbon footprint of C2in maizeland system was highest in all treatments, its value was6.63kg CO2eq·kg-1. Conversely, the carbon footprint in H2was3.85kg CO2eq·kg-1, which was the lowest. Through the ANOVA, we knew that the Pearson correlationcoefficient between the economic yield of maize and its corresponding carbon footprint was-0.111(p=0.260), thePearson correlation coefficient between the CO2eq amount of maize organisms aboveground and its correspondingcarbon footprint was0.284(p=0.046), which showed that: It was possible for us to achieve improving the maizeeconomic yield in the condition of decreasing the carbon footprint in maize land system. Making sure that the maizeresidues could be used in a scientific way and avoiding its burning in a large quantity could be seemed as an effectivemeasure to decrease the carbon footprint in maize land system. Combined with the statistical analysis results, underthe condition of flat and middle irrigation level, and combining the completely mulching measure, the highest carbonfootprint in maize land system could be gotten, and combining the the half one, the lowest carbon footprint in maizeland system could be gotten, which was the optimal combination for decreasing the carbon footprint in maize landsystem.