Articles
Extending the growth period of green manure can reduce the risk of soil organic matter loss due to priming effects
Article number
1375_31
Pages
233 – 242
Language
English
Abstract
Green manure is often grown and incorporated into the soil to increase soil organic matter (SOM) and is considered to be one of the sustainable agricultural practices.
However, contrary to expectations, this method often results in a decrease in SOM due to priming effects, which in turn leads to the further release of CO2 into the atmosphere.
In this study, we tested whether increasing the growth period of green manure in a realistic cropping system can increase SOM and also increase the yield of subsequently planted vegetables.
Field experiments were conducted using sorghum (Sorghum bicolor) as a summer green manure.
Three green manure treatments (NGM: no green manure, 2mGM: standard green manure practice of growing green manure for two months and leaving the field one month after application, 3mGM: growing green manure for three months) were tested in combination with two chemical fertilization treatments (CF: conventional fertilization, NF: no fertilization). After each green manure treatment, cabbage or lettuce was grown as fall and spring crops.
Biomass of sorghum, carbon-nitrogen (CN) ratio, vegetable yield, and soil chemical properties were investigated for 3 years.
The biomass of sorghum was 2-5 times higher and the CN ratio 2-3 times higher under 3mGM compared to those under 2mGM. SOM increased under the combination of 3mGM and CF but did not increase under the combination of 2mGM and CF, which is the standard practice for green manure application.
Vegetable yields increased after two years of sorghum incorporation.
Increasing the biomass and the CN ratio by extending the growing period of green manure seems to be a promising method to increase both vegetable yield and SOM.
However, contrary to expectations, this method often results in a decrease in SOM due to priming effects, which in turn leads to the further release of CO2 into the atmosphere.
In this study, we tested whether increasing the growth period of green manure in a realistic cropping system can increase SOM and also increase the yield of subsequently planted vegetables.
Field experiments were conducted using sorghum (Sorghum bicolor) as a summer green manure.
Three green manure treatments (NGM: no green manure, 2mGM: standard green manure practice of growing green manure for two months and leaving the field one month after application, 3mGM: growing green manure for three months) were tested in combination with two chemical fertilization treatments (CF: conventional fertilization, NF: no fertilization). After each green manure treatment, cabbage or lettuce was grown as fall and spring crops.
Biomass of sorghum, carbon-nitrogen (CN) ratio, vegetable yield, and soil chemical properties were investigated for 3 years.
The biomass of sorghum was 2-5 times higher and the CN ratio 2-3 times higher under 3mGM compared to those under 2mGM. SOM increased under the combination of 3mGM and CF but did not increase under the combination of 2mGM and CF, which is the standard practice for green manure application.
Vegetable yields increased after two years of sorghum incorporation.
Increasing the biomass and the CN ratio by extending the growing period of green manure seems to be a promising method to increase both vegetable yield and SOM.
Authors
K. Miyazawa, Y.C. Chen, S. Ishiguro
Keywords
cabbage, lettuce, carbon sequestration, cover crop
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