Abstract
The tillage depth plays a critical role in solving soil compaction - a global problem of soil degradation. However, to date, there are few research reported about tillage depth, and the standard of optimum tillage depth is lacking. Therefore, we conducted a meta-analysis to quantify the effect of tillage depths on crop yield across a global scale, and then to analysis their influence factors such as local climate, soil properties, and managements. Moreover, a global distribution of the optimal tillage depths was estimated by using a random-forest model. Overall, our result demonstrated that crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations from 202 studies and 109 publications. Visibly, 35 cm hence became the optimum tillage depth of WMS across the world, while it varies with different regions. Furthermore, higher crop yields observed in areas with a humid climate, high clay contents, and large bulk density under the optimal depth 40, 35 and 45 cm, respectively. In contrast, a lower yield was observed in areas with arid climates, silty and sandy soils, and lower bulk density within optimal depth of 25 cm, 30 cm, and 25 to 35 cm. Human management efforts, including fertilizer addition, irrigation, straw returning, and changing of cropping system or crop species mostly increased the crop yield under deep tillage. Particularly, our meta-analysis indicated that straw returning needs a greater depth. Finally, we predicted the distributions of optimum depths, which showed that 30 and 35 cm were the optimum tillage depths in the temperate and tropical regions, and the total crop yields of global WMS increased by 2689 million tons per year under the optimal tillage depth, compared with the conventional tillage.
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Claims 16
Claim · model-written summary
Tillage depths from 25 to 35 cm increased crop yield of wheat, maize and soybean relative to conventional tillage.
- Taxon
- wheat, maize and soybean
Glycine max
Triticum aestivum
Zea mayse1 - Treatment
- tillage depths from 25 to 35 cme1
- Outcome
- crop yielde1
- Direction
- increasede1
- Comparator
- conventional tillagee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
Claim · model-written summary
Deeper tillage above 35 cm reduced crop yield of wheat, maize and soybean relative to conventional tillage.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Treatment
- higher depth of deep tillagee1
- Outcome
- crop yielde1
- Direction
- reducede1
- Comparator
- conventional tillagee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
Claim · model-written summary
The optimum tillage depth of WMS across the world was 35 cm, varying among regions.
Verbatim
e1“Visibly, 35 cm hence became the optimum tillage depth of WMS across the world, while it varies with different regions”
Claim · model-written summary
Crop yield was higher in areas with a humid climate under the optimal tillage depth of 40 cm.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Outcome
- crop yielde2
- Direction
- highere2
- Qualifier
- under the optimal depth 40, 35 and 45 cm, respectivelye2
- Setting
- areas with a humid climatee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
e2“higher crop yields observed in areas with a humid climate, high clay contents, and large bulk density under the optimal depth 40, 35 and 45 cm, respectively”
Claim · model-written summary
Crop yield was higher in soils with high clay contents under the optimal tillage depth of 35 cm.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Outcome
- crop yielde2
- Direction
- highere2
- Qualifier
- under the optimal depth 40, 35 and 45 cm, respectivelye2
- Setting
- high clay contentse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
e2“higher crop yields observed in areas with a humid climate, high clay contents, and large bulk density under the optimal depth 40, 35 and 45 cm, respectively”
Claim · model-written summary
Crop yield was higher with large bulk density under the optimal tillage depth of 45 cm.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Outcome
- crop yielde2
- Direction
- highere2
- Qualifier
- under the optimal depth 40, 35 and 45 cm, respectivelye2
- Setting
- large bulk densitye2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
e2“higher crop yields observed in areas with a humid climate, high clay contents, and large bulk density under the optimal depth 40, 35 and 45 cm, respectively”
Claim · model-written summary
Crop yield was lower in areas with arid climates within the optimal tillage depth of 25 cm.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Outcome
- yielde2
- Direction
- lowere2
- Qualifier
- within optimal depth of 25 cm, 30 cm, and 25 to 35 cme2
- Setting
- areas with arid climatese2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
e2“a lower yield was observed in areas with arid climates, silty and sandy soils, and lower bulk density within optimal depth of 25 cm, 30 cm, and 25 to 35 cm”
Claim · model-written summary
Crop yield was lower in silty and sandy soils within the optimal tillage depth of 30 cm.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Outcome
- yielde2
- Direction
- lowere2
- Qualifier
- within optimal depth of 25 cm, 30 cm, and 25 to 35 cme2
- Setting
- silty and sandy soilse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
e2“a lower yield was observed in areas with arid climates, silty and sandy soils, and lower bulk density within optimal depth of 25 cm, 30 cm, and 25 to 35 cm”
Claim · model-written summary
Crop yield was lower with lower bulk density within the optimal tillage depth of 25 to 35 cm.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Outcome
- yielde2
- Direction
- lowere2
- Qualifier
- within optimal depth of 25 cm, 30 cm, and 25 to 35 cme2
- Setting
- lower bulk densitye2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
e2“a lower yield was observed in areas with arid climates, silty and sandy soils, and lower bulk density within optimal depth of 25 cm, 30 cm, and 25 to 35 cm”
Claim · model-written summary
Fertilizer addition mostly increased crop yield under deep tillage.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Treatment
- fertilizer additione2
- Outcome
- crop yielde2
- Direction
- increasede2
- Qualifier
- under deep tillagee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
e2“Human management efforts, including fertilizer addition, irrigation, straw returning, and changing of cropping system or crop species mostly increased the crop yield under deep tillage”
Claim · model-written summary
Irrigation mostly increased crop yield under deep tillage.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Treatment
- irrigatione2
- Outcome
- crop yielde2
- Direction
- increasede2
- Qualifier
- under deep tillagee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
e2“Human management efforts, including fertilizer addition, irrigation, straw returning, and changing of cropping system or crop species mostly increased the crop yield under deep tillage”
Claim · model-written summary
Straw returning mostly increased crop yield under deep tillage.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Treatment
- straw returninge2
- Outcome
- crop yielde2
- Direction
- increasede2
- Qualifier
- under deep tillagee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
e2“Human management efforts, including fertilizer addition, irrigation, straw returning, and changing of cropping system or crop species mostly increased the crop yield under deep tillage”
Claim · model-written summary
Changing of cropping system or crop species mostly increased crop yield under deep tillage.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Treatment
- changing of cropping system or crop speciese2
- Outcome
- crop yielde2
- Direction
- increasede2
- Qualifier
- under deep tillagee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
e2“Human management efforts, including fertilizer addition, irrigation, straw returning, and changing of cropping system or crop species mostly increased the crop yield under deep tillage”
Claim · model-written summary
Straw returning needs a greater tillage depth.
- Taxon
- wheat, maize and soybeanGlycine maxTriticum aestivumZea mayse1
- Treatment
- straw returninge2
- Outcome
- depthe2
- Direction
- greatere2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“crop yield first increased within tillage depths from 25 to 35 cm, and then reduced under higher depth of deep tillage compared to conventional tillage, according to 1109 wheat, maize and soybean (WMS) yield observations”
e2“Particularly, our meta-analysis indicated that straw returning needs a greater depth”
Claim · model-written summary
Predicted optimum tillage depths were 30 and 35 cm in temperate and tropical regions.
Verbatim
e1“Finally, we predicted the distributions of optimum depths, which showed that 30 and 35 cm were the optimum tillage depths in the temperate and tropical regions, and the total crop yields of global WMS increased by 2689 million tons per year under the optimal tillage depth, compared with the conventional tillage”
Claim · model-written summary
Optimal tillage depth increased predicted total crop yield of global WMS by 2689 million tons per year compared with conventional tillage.
Verbatim
e1“Finally, we predicted the distributions of optimum depths, which showed that 30 and 35 cm were the optimum tillage depths in the temperate and tropical regions, and the total crop yields of global WMS increased by 2689 million tons per year under the optimal tillage depth, compared with the conventional tillage”
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