Carbon Sequestration as a Function of Intercropping Management Practice and Different Nitrogenous Fertilizer Types

This study has been carried out through an experiment conducted at El-Giza Agricultural Research Station to examine the short-term effects (3 years) of two cropping patterns-based on intercropping system and N fertilization on quantifying of crop& soil carbon sequestration and soil carbon dioxide emissions targeting to test the ability of this management to mitigate global warming which produced from increased concentration of atmospheric CO2which would essentially reflect upon climate change mitigation . Also, the impact of soil temperature and moisture changes as factors affected such emissions have put into consideration. The first intercropping pattern has been sunflower/cowpea (Helianthusannuus, va.Sakha, 53/Vigna unguiculata. local). Second intercropping pattern has been wheat/peas (Triticum aestivum L va, Sakha 94/Pisum sativum Lva, Master b.). The first intercropping pattern has been arranged in 2:2,2:3 rows of sunflower: cowpea, sole sunflower and sole cowpea (4 configurations) while the 3: 2,5:2 rows of wheat: peas , sole peas and sole wheat (4 configurations) have been done for the second pattern. The N-fertilizers have been urea and ureaform (slow release nitrogen fertilizer); in rate of 60kg N fedfor sunflower/cowpea intercrop,110 kg N fed for wheat/peas intercrop, 30 kg N fedforsole sunflower and 30 kg N fedfor sole cowpea from urea added for every season.100kg N fed for sunflower/cowpea intercrop,50kgN fed for sole sunflower and 50kgN fed for sole cowpea from ureaform added for every two seasons. Wheat/peas intercrop; sole wheat and sole peas (in second season) have not been taken N-fertilizer but grown on the residual ureaform-N. Soil CO2 emissions have been weekly measured from October 3, 2010 to May 9, 2013, us ingstatic chamber technique. Such emissions have been absorbed through NaOH followed by HCl titration. Also, soil temperature and moisture have been weekly recorded. Soil sampling after harvest has been taken to determine some physical and chemical properties. After three years of practicing this management, the results indicate that, under the conditions of this experiment, soil temperature varied between 12and 45Co at 5 cm depth, soil moisture varied between 2 and 55% at the same depth. Statistically, they have shown no or poor correlations with soil emitted-CO2.The quantities of soil-CO2 emitted from irrigated plot treatments and determined in summer seasons have been higher than those of non-irrigated ones and those determined in winter seasons. Intercrops patterns and UF fertilizer have been contributed to obtain a lower emitted CO2 quantities from soil compared to sole crops patterns and urea fertilizer. The obtained yield from intercrops patterns treatments and UF fertilizer have been higher than those of sole crops patterns ones and urea fertilizer. Intercrops patterns and UF fertilizer have been found to be efficient in increasing sequestered carbon either in crop biomass or in soil; the crop sequestered-C relative increase for intercrops to sole crops values have seasonally varied between 42.06 and 77.75% for sunflower /cowpea intercrops and between -12.01 and 0.46% for wheat/peas ones. The crop sequestered-C relative increase for UF to urea values have varied between 6.78 and 10.51%under sunflower/cowpea intercrops and between14.60 and30.05 % under wheat/ peas ones. Regarding soil sequestered carbon over 3 years ,sequestered-C relative increase for intercrops to sole crops has amounted 5.83% and for UF to urea amounted 47.08%. The marked gradual improvement in soil organic matter content, EC, pH, BD, available-N, stable aggregates% and porosity have positively reflected on changes in the soil sequestered carbon quantities.