Effects of different tillage practices and nitrogen application rate on carbon dioxide emissions and carbon balance in rain-fed maize crops

doi:10.11686/cyxb2020136

Abstract

Abstract:

Full-film double furrow sowing technology is one of the main production technologies of dryland maize on the Loess Plateau in recent years. Study of the influence of different tillage methods on soil CO₂ emission from dryland maize farmland is highly relevant to understanding of carbon cycling， reducing emissions， and selection of appropriate management measures in farmland systems. This research evaluated the CO₂ emission and carbon balance of dryland maize farmland under four tillage methods （subsoiling， no-tillage， rotary tillage and ploughing）. combined with two commonly used nitrogen application rates （200 and 300 kg·ha^-1） in field experiments. It was found that the variation in soil CO₂ emission rate reflected variation in atmospheric temperature. The maximum and minimum values occurred around 12：00-14：00 and 4：00-6：00， respectively. The soil CO₂ emission rate during the growth period showed a trend of initial increase and then decrease with increasing plant maturity. The pattern of variation in each treatment with time was basically the same. The peak soil CO₂ emission rate appeared in the stem elongation， head emergence and flowering periods， and then decreased to the lowest rate in the ripening period. The total carbon emission and carbon emission efficiency over the entire growth period were significantly higher in the ploughing treatment than other treatments （P<0.05）， and there were no significant differences （P>0.05） between the other tillage methods. The total soil CO₂ emission at a fertilizer application rate of 300 kg·ha^-1 was significantly higher than 200 kg·ha^-1（P<0.05）. The net ecosystem productivity and carbon sequestration potential of the maize field cropping system were significantly higher under subsoiling than other treatments （P<0.05）， but the two nitrogen rates did not differ significantly （P>0.05）. In conclusion， based on these results， the combination of subsoiling and the traditional nitrogen application rate （200 kg N·ha^-1） is the preferred management mode for maize in the Loess Plateau arid region， from the perspective of carbon sequestration and emission reduction.

Key words: soil CO₂ emission, carbon balance, tillage methods, nitrogen fertilizer, maize field

Peng QI, Xiao-jiao WANG, Yi-ming YAO, Xiao-long CHEN, Jun WU, Li-qun CAI. Effects of different tillage practices and nitrogen application rate on carbon dioxide emissions and carbon balance in rain-fed maize crops[J]. Acta Prataculturae Sinica, 2021, 30(1): 96-106.

Figures/Tables 8

Fig.1 Monthly precipitation distribution in 2018

Table 1 Soil chemical and physical properties

土层

Soil layer

(cm)

容重

Bulk density

(g·cm^-3)

有机碳

Organic carbon

(g·kg^-1)

全氮

Total nitrogen

(g·kg^-1)

全磷

Total phosphorus

(g·kg^-1)

速效磷

Available phosphorus(mg·kg^-1）

速效钾

Available potassium

(mg·kg^-1）

Fig.2 Soil CO2 flux in different treatments of tillage and nitrogen application

Table 2 Daily average soil CO2 flux in different treatments of tillage and nitrogen application

项目 Item	处理 Treatments	土壤CO₂排放速率 Soil CO₂ flux （μmol·m^-2·s^-1）
耕作方式 Tillage practice	T₁	4.62±0.17a
	T₂	4.61±0.21a
	T₃	4.42±0.32b
	T₄	4.52±0.42ab
施氮量 Nitrogen application rate	N₁	4.51±0.58a
施氮量 Nitrogen application rate	N₂	4.58±0.52a
耕作方式 Tillage practice (T)		*
施氮量 Nitrogen application rate (N)		ns
耕作方式×施氮量 T×N		ns

Fig.3 Growth stage changes of soil CO2 flux in different treatments of tillage and nitrogen application

Table 3 Average soil CO2 flux during growth period in different treatments of tillage and nitrogen application

项目 Item	处理 Treatments	土壤CO₂排放速率 Soil CO₂ flux （μmol·m^-2·s^-1）
耕作方式 Tillage practice	T₁	3.91±0.23a
	T₂	3.62±0.34b
	T₃	3.60±0.32b
	T₄	3.56±0.42b
施氮量 Nitrogen application rate	N₁	3.58±0.39b
施氮量 Nitrogen application rate	N₂	3.77±0.27a
耕作方式 Tillage practice (T)		*
施氮量 Nitrogen application rate （N）		*
耕作方式×施氮量 T×N		ns

Table 4 Effects of crop yield and carbon emission efficiency in different treatments of tillage and nitrogen application

项目 Item	处理 Treatments	籽粒产量 Crop yield (kg·hm^-2)	总生物量 Total biomass (kg·hm^-2)	土壤碳排放量 CE (kg C·hm^-2)	CEE (kg·kg^-1)
耕作方式 Tillage practice	T₁	13025.73±907.56c	29148.81±681.03bc	7213.78±356.40a	0.56±0.15a
	T₂	13335.49±982.24b	30212.85±989.40ab	6620.62±427.06b	0.50±0.16b
	T₃	13993.19±869.69a	30763.54±825.62a	6451.60±376.37b	0.46±0.05b
	T₄	13078.00±375.38c	29022.36±778.87c	6436.87±218.47b	0.49±0.06b
施氮量 Nitrogen application rate	N₁	13056.28±945.77a	29316.00±963.63a	6556.84±461.79b	0.50±0.20a
施氮量 Nitrogen application rate	N₂	13659.92±751.72a	30257.77±816.82a	6804.59±540.28a	0.51±0.13a
耕作方式 Tillage practice (T)		*	*	**	**
施氮量 Nitrogen application rate (N)		ns	ns	*	ns
耕作方式×施氮量T×N		ns	ns	ns	ns

Table 5 The carbon balance of farmland system during the growth period in different treatments of tillage and nitrogen application

项目 Item	处理 Treatments	碳固定量 NPP-C (kg C·hm^-2)	微生物呼吸 Rm-C (kg C·hm^-2)	净生态系统生产力 NEP-C (kg C·hm^-2)	NPP-C/CE比值 NPP-C/CE ratio
耕作方式Tillage practice	T₁	13989.55±321.89bc	6239.93±302.28a	7749.63±396.25c	1.94±0.06c
	T₂	14489.12±571.92ab	5726.84±369.40b	8762.29±428.38b	2.19±0.14b
	T₃	14781.00±386.29a	5580.63±325.56b	9200.37±254.26a	2.30±0.07a
	T₄	13936.16±370.86c	5567.89±188.98b	8368.29±387.45b	2.17±0.09b
施氮量 Nitrogen application rate	N₁	14066.84±513.54a	5671.67±398.46a	8395.17±412.21a	2.15±0.18a
施氮量 Nitrogen application rate	N₂	14531.08±561.07a	5885.89±466.34a	8645.11±487.35a	2.14±0.15a
耕作方式 Tillage practice (T)		*	**	**	**
施氮量 Nitrogen application rate (N)		ns	*	ns	ns
耕作方式×施氮量T $×$ N		ns	ns	ns	ns

Table 5 The carbon balance of farmland system during the growth period in different treatments of tillage and nitrogen application

项目 Item	处理 Treatments	碳固定量 NPP-C (kg C·hm^-2)	微生物呼吸 Rm-C (kg C·hm^-2)	净生态系统生产力 NEP-C (kg C·hm^-2)	NPP-C/CE比值 NPP-C/CE ratio
耕作方式Tillage practice	T₁	13989.55±321.89bc	6239.93±302.28a	7749.63±396.25c	1.94±0.06c
	T₂	14489.12±571.92ab	5726.84±369.40b	8762.29±428.38b	2.19±0.14b
	T₃	14781.00±386.29a	5580.63±325.56b	9200.37±254.26a	2.30±0.07a
	T₄	13936.16±370.86c	5567.89±188.98b	8368.29±387.45b	2.17±0.09b
施氮量 Nitrogen application rate	N₁	14066.84±513.54a	5671.67±398.46a	8395.17±412.21a	2.15±0.18a
施氮量 Nitrogen application rate	N₂	14531.08±561.07a	5885.89±466.34a	8645.11±487.35a	2.14±0.15a
耕作方式 Tillage practice (T)		*	**	**	**
施氮量 Nitrogen application rate (N)		ns	*	ns	ns
耕作方式×施氮量T $×$ N		ns	ns	ns	ns

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