Abstract
Secondary and micronutrients are important in enhancing crop productivity; yet, they are hardly studied in sub-Sahara Africa. In this region, the main focus has been on macronutrients but there is emerging though scattered evidence of crop productivity limitations by the secondary and micronutrients. Elsewhere, widespread deficiencies of these nutrients are associated with stagnation of yields. Here, we undertake a meta-analysis using 40 articles reporting crop response to secondary and micronutrients to (1) determine the productivity increase of crops and nutrient use efficiency associated with these nutrients, and (2) provide synthesis of responses to secondary nutrients and micronutrients in sub-Sahara Africa. This study used 757 yield data rows (530 from publications and 227 from Africa Soil Information Service) from field trials carried out in SSA between 1969 and 2013 in 14 countries. Data from publications constituted response to S (49.4%), Zn (23.0%), S and micronutrient combinations (11.5%), and <10% each for Cu, Mo, Fe, and B. Data from Africa Soil Information Service were all for S and micronutrient combinations. Of the two sources, most yield data are for maize (73.6%), followed by sorghum (6.7%) and wheat (6.1%) while rice, cowpea, faba bean, tef, and soybean each accounted for less than 5%. The major points are the following: (1) application of S and micronutrients increased maize yield by 0.84 t ha−1 (i.e., 25%) over macronutrient only treatment and achieved agronomic efficiencies (kilograms of grain increase per kilogram of micronutrient added) between 38 and 432 and (2) response ratios were >1 for S and all micronutrients, i.e., the probability of response ratio exceeding 1 was 0.77 for S and 0.83 for Zn, 0.95 for Cu, and 0.92 for Fe, and indicates positive crop response for a majority of farmers. We conclude that S and micronutrients are holding back crop productivity especially on soils where response to macronutrients is low and that more research is needed to unravel conditions under which application of S and micronutrients may pose financial risks.
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Claims 9
Claim · model-written summary
S and micronutrients increased maize yield by 0.84 t ha−1 over macronutrients alone.
- Treatment
- application of S and micronutrientse0
- Outcome
- maize yielde0
- Direction
- increasede0
- Value
- 0.84 t ha−1e0
- Comparator
- macronutrient only treatmente0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The major points are the following: (1) application of S and micronutrients increased maize yield by 0.84 t ha−1 (i.e., 25%) over macronutrient only treatment and achieved agronomic efficiencies (kilograms of grain increase per kilogram of micronutrient added) between 38 and 432 and (2) response ratios were >1 for S and all micronutrients, i.e., the probability of response ratio exceeding 1 was 0.77 for S and 0.83 for Zn, 0.95 for Cu, and 0.92 for Fe, and indicates positive crop response for a majority of farmers.”
Claim · model-written summary
S and micronutrients increased maize yield by 25% over macronutrients alone.
- Treatment
- application of S and micronutrientse0
- Outcome
- maize yielde0
- Direction
- increasede0
- Value
- 25%e0
- Comparator
- macronutrient only treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The major points are the following: (1) application of S and micronutrients increased maize yield by 0.84 t ha−1 (i.e., 25%) over macronutrient only treatment and achieved agronomic efficiencies (kilograms of grain increase per kilogram of micronutrient added) between 38 and 432 and (2) response ratios were >1 for S and all micronutrients, i.e., the probability of response ratio exceeding 1 was 0.77 for S and 0.83 for Zn, 0.95 for Cu, and 0.92 for Fe, and indicates positive crop response for a majority of farmers.”
Claim · model-written summary
Agronomic efficiencies from S and micronutrients were between 38 and 432.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The major points are the following: (1) application of S and micronutrients increased maize yield by 0.84 t ha−1 (i.e., 25%) over macronutrient only treatment and achieved agronomic efficiencies (kilograms of grain increase per kilogram of micronutrient added) between 38 and 432 and (2) response ratios were >1 for S and all micronutrients, i.e., the probability of response ratio exceeding 1 was 0.77 for S and 0.83 for Zn, 0.95 for Cu, and 0.92 for Fe, and indicates positive crop response for a majority of farmers.”
Claim · model-written summary
The probability of a response ratio above one for S was 0.77.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The major points are the following: (1) application of S and micronutrients increased maize yield by 0.84 t ha−1 (i.e., 25%) over macronutrient only treatment and achieved agronomic efficiencies (kilograms of grain increase per kilogram of micronutrient added) between 38 and 432 and (2) response ratios were >1 for S and all micronutrients, i.e., the probability of response ratio exceeding 1 was 0.77 for S and 0.83 for Zn, 0.95 for Cu, and 0.92 for Fe, and indicates positive crop response for a majority of farmers.”
Claim · model-written summary
The probability of a response ratio above one for Zn was 0.83.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The major points are the following: (1) application of S and micronutrients increased maize yield by 0.84 t ha−1 (i.e., 25%) over macronutrient only treatment and achieved agronomic efficiencies (kilograms of grain increase per kilogram of micronutrient added) between 38 and 432 and (2) response ratios were >1 for S and all micronutrients, i.e., the probability of response ratio exceeding 1 was 0.77 for S and 0.83 for Zn, 0.95 for Cu, and 0.92 for Fe, and indicates positive crop response for a majority of farmers.”
Claim · model-written summary
The probability of a response ratio above one for Cu was 0.95.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The major points are the following: (1) application of S and micronutrients increased maize yield by 0.84 t ha−1 (i.e., 25%) over macronutrient only treatment and achieved agronomic efficiencies (kilograms of grain increase per kilogram of micronutrient added) between 38 and 432 and (2) response ratios were >1 for S and all micronutrients, i.e., the probability of response ratio exceeding 1 was 0.77 for S and 0.83 for Zn, 0.95 for Cu, and 0.92 for Fe, and indicates positive crop response for a majority of farmers.”
Claim · model-written summary
The probability of a response ratio above one for Fe was 0.92.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The major points are the following: (1) application of S and micronutrients increased maize yield by 0.84 t ha−1 (i.e., 25%) over macronutrient only treatment and achieved agronomic efficiencies (kilograms of grain increase per kilogram of micronutrient added) between 38 and 432 and (2) response ratios were >1 for S and all micronutrients, i.e., the probability of response ratio exceeding 1 was 0.77 for S and 0.83 for Zn, 0.95 for Cu, and 0.92 for Fe, and indicates positive crop response for a majority of farmers.”
Claim · model-written summary
The authors conclude S and micronutrients constrain crop productivity especially where macronutrient response is low.
Verbatim
e0“We conclude that S and micronutrients are holding back crop productivity especially on soils where response to macronutrients is low”
Claim · model-written summary
The authors call for research into conditions under which these nutrient applications pose financial risks.
Verbatim
e0“more research is needed to unravel conditions under which application of S and micronutrients may pose financial risks.”
t0“Application of secondary nutrients and micronutrients increases crop yields in sub-Saharan Africa”
The same questions in other papers
micronutrient · yield · Zea mays (maize)Results differ
72 papers in the same direction as this paper · 6 in the opposite direction · 1 reporting no difference from an alternative
- positive
- no effect
- no effect
76 papers more in this group
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