Greenhouse Gas Emission from Cauliflower Grown under Different Nitrogen Rates and Mulches

A field experiment was conducted during the two successive seasons of 2012/2013 and 2013/2014 at El-Bosaily farm, El-Behira governorate, Egypt, to study the effect of different nitrogen rates and mulch treatments on plant growth and yield of cauliflower (Brassica oleracia var. botrytis). The study includes three mulch treatments (transparent and black polyethylene sheets, and bare soil as a control) and four N rates 30, 45, 60 and 75 kg/feddan (1 feddan = 4200 m2 and hectare = 2.4 feddan) designed in a split plots with three replicates. The greenhouse gas (GHG) emissions of N2O and CO2 from N fertilization were calculated for different treatments. Regarding the polyethylene (PE) mulch, data revealed that transparent PE recorded the highest significant values of cauliflower growth characters during the two studied seasons. Increasing N rate up to 60 kg/feddan enhanced cauliflower growth using different polyethylene mulch treatments; yield was not increased significantly with increasing N rate up to 75 kg/feddan. The highest significant cauliflower yield was obtained by using 60 kg N/feddan combined with transparent mulch, while the lowest yield was obtained in case of 30 kg N/feddan combined with bare soil treatment. Chemical analysis of cauliflower leaves at harvest revealed that the percentage of N, P and K increased significantly with increasing N rate up to 75 kg/feddan. Polyethylene mulch treatments increased N, P and K percentages significantly in comparison with bare soil treatment. Moreover, the greenhouse gas emissions (N2O and CO2) from fertilization increased but the emission rates (kg CO2/kg yield) were decreased by increasing N rate due to the highest cauliflower production. The highest yield with low emission was obtained by 60 kg N/feddan.