Abstract
SUMMARY Conservation agriculture (CA) systems are based on minimal soil disturbance, crop residue retention and crop rotation. Although the capacity of rotations to break pest and disease cycles is generally recognized, other benefits of crop rotations in CA systems are seldom acknowledged and little understood. We monitored different conventional and CA cropping systems over the period from 2005 to 2009 in a multi-seasonal trial in Monze, southern Zambia. Both monocropped maize and different maize rotations including cotton and the green manure cover crop sunnhemp ( Crotalaria juncea ) were compared under CA conditions, with the aim of elucidating the effects of crop rotations on soil quality, soil moisture relations and maize productivity. Infiltration, a sensitive indicator of soil quality, was significantly lower on conventionally ploughed plots in all cropping seasons compared to CA plots. Higher water infiltration rate led to greater soil moisture content in CA maize treatments seeded after cotton. Earthworm populations, total carbon and aggregate stability were also significantly higher on CA plots. Improvements in soil quality resulted in higher rainfall use efficiency and higher maize grain yield on CA plots especially those in a two- or three-year rotation. In the 2007/08 and 2008/2009 season, highest yields were obtained from direct-seeded maize after sunnhemp, which yielded 74% and 136% more than maize in the conventionally ploughed control treatment with a continuous maize crop. Even in a two-year rotation (maize-cotton), without a legume green manure cover crop, 47% and 38% higher maize yields were recorded compared to maize in the conventionally ploughed control in the two years, respectively. This suggests that there are positive effects from crop rotations even in the absence of disease and pest problems. The overall profitability of each system will, however, depend on markets and prices, which will guide the farmer's decision on which, if any, rotation to choose.
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Claims 11
Claim · model-written summary
Conventional ploughing reduced infiltration relative to conservation agriculture across seasons.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Infiltration, a sensitive indicator of soil quality, was significantly lower on conventionally ploughed plots in all cropping seasons compared to CA plots”
e1“maize productivity”
Claim · model-written summary
CA maize after cotton had higher soil moisture content with higher infiltration.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Higher water infiltration rate led to greater soil moisture content in CA maize treatments seeded after cotton”
Claim · model-written summary
CA plots had significantly higher earthworm populations.
- Treatment
- CA plotse0
- Outcome
- Earthworm populationse0
- Direction
- highere0
- Comparator
- conventionally ploughed plotse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Earthworm populations, total carbon and aggregate stability were also significantly higher on CA plots”
e1“conventionally ploughed plots in all cropping seasons compared to CA plots”
e2“maize productivity”
Claim · model-written summary
CA plots had significantly higher total carbon.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Earthworm populations, total carbon and aggregate stability were also significantly higher on CA plots”
e1“conventionally ploughed plots in all cropping seasons compared to CA plots”
e2“maize productivity”
Claim · model-written summary
CA plots had significantly higher aggregate stability.
- Treatment
- CA plotse0
- Outcome
- aggregate stabilitye0
- Direction
- highere0
- Comparator
- conventionally ploughed plotse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Earthworm populations, total carbon and aggregate stability were also significantly higher on CA plots”
e1“conventionally ploughed plots in all cropping seasons compared to CA plots”
e2“maize productivity”
Claim · model-written summary
CA improved maize rainfall use efficiency, especially in two- or three-year rotations.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Improvements in soil quality resulted in higher rainfall use efficiency and higher maize grain yield on CA plots especially those in a two- or three-year rotation”
Claim · model-written summary
CA improved maize grain yield, especially in two- or three-year rotations.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Improvements in soil quality resulted in higher rainfall use efficiency and higher maize grain yield on CA plots especially those in a two- or three-year rotation”
Claim · model-written summary
Direct-seeded maize after sunnhemp yielded 74% more than continuous conventional maize in 2007/08.
- Treatment
- direct-seeded maize after sunnhempe0
- Outcome
- yieldse0
- Direction
- moree0
- Value
- 74%e0
- Qualifier
- 2007/08e0
- Comparator
- maize in the conventionally ploughed control treatment with a continuous maize crope0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the 2007/08 and 2008/2009 season, highest yields were obtained from direct-seeded maize after sunnhemp, which yielded 74% and 136% more than maize in the conventionally ploughed control treatment with a continuous maize crop”
Claim · model-written summary
Direct-seeded maize after sunnhemp yielded 136% more than continuous conventional maize in 2008/2009.
- Treatment
- direct-seeded maize after sunnhempe0
- Outcome
- yieldse0
- Direction
- moree0
- Value
- 136%e0
- Qualifier
- 2008/2009e0
- Comparator
- maize in the conventionally ploughed control treatment with a continuous maize crope0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the 2007/08 and 2008/2009 season, highest yields were obtained from direct-seeded maize after sunnhemp, which yielded 74% and 136% more than maize in the conventionally ploughed control treatment with a continuous maize crop”
Claim · model-written summary
The maize-cotton rotation raised maize yield by 47% versus continuous conventional maize in the first reported year.
- Treatment
- two-year rotation (maize-cotton)e0
- Outcome
- maize yieldse0
- Direction
- highere0
- Value
- 47%e0
- Comparator
- maize in the conventionally ploughed controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Even in a two-year rotation (maize-cotton), without a legume green manure cover crop, 47% and 38% higher maize yields were recorded compared to maize in the conventionally ploughed control in the two years, respectively”
Claim · model-written summary
The maize-cotton rotation raised maize yield by 38% versus continuous conventional maize in the second reported year.
- Treatment
- two-year rotation (maize-cotton)e0
- Outcome
- maize yieldse0
- Direction
- highere0
- Value
- 38%e0
- Comparator
- maize in the conventionally ploughed controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Even in a two-year rotation (maize-cotton), without a legume green manure cover crop, 47% and 38% higher maize yields were recorded compared to maize in the conventionally ploughed control in the two years, respectively”
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