CO₂ Emissions per Unit of Yield and Water Use for Lettuce Grown in Soil Fertilized withManure and Irrigated at Different Intervals

Organic fertilization plays a crucial role in enhancing crop yields and

water efficiency in agriculture. Nevertheless, it is equally vital to consider how

irrigation practices can impact the potential for CO2 emissions during short-term

crop production. A field study was conducted on curly lettuce, comparing two

doses of cattle manure (M1 and M2, with approximately 3% and 4.5% soil organic

matter content, respectively) with mineral fertilization (F). Irrigation intervals

were set at every two (IR1) and four days (IR2). The M2IR1 treatment had the

highest seasonal average CO2 emission of 0.909 g CO2 m-2, which was 90.2%

higher than in the FIR1 treatment. The emission quantities exhibited a strong

linear correlation with soil organic matter and moisture contents. The M2

treatment had the highest marketable yield at 7.84 kg m-2, which was 5.7% and

12.7% higher than in the M1 and F treatments, respectively. The M2IR2 treatment

had the highest emission per kg yield at 143.5 g CO2, which was 83.7% higher

than the FIR1 treatment. The M2 treatment provided lower evapotranspiration

values. CO2 emission per m3 of water use in the M2IR2 treatment was the highest

at 8.50 kg CO2, which was 217.2% greater than in the FIR1 treatment. The study

concluded that reducing water usage and increasing yields under manure-fertilized

conditions may not lower CO2 emissions per unit of yield and water use for lettuce

in the short-term period.