Abstract
Deficiencies of secondary and micronutrients (SMNs) are major causes of low maize yields in poorly responsive soils. This phenomenon minimizes the agronomic efficiency of N, P and K fertilizers and consequently result in a dwindling economic benefit associated with their use. Therefore, 18 on-farm trials were conducted in western Kenya during two cropping seasons to assess maize response to three NPK amendments; (i) N, P, K, Ca, Zn and Cu (inorganic and organic); (ii) N, P, K, Ca, Zn and Cu (inorganic) and (iii) N, P K, Zn and Cu (inorganic) and evaluate the profitability of their use compared to additions of only N, P and K fertilizers. In this set of experiments, maize response to any amendment refers to a yield increase of ≥2 t ha−1 above control and could be categorized in three clusters. Cluster 1, comprising of nine sites, maize responded to all amendments. Cluster 2, holding six sites, maize responded only to one amendment, N, P, K, Ca, Zn and Cu (inorganic). In this cluster, (2), emerging S, Mg and Cu deficiencies may still limit maize production. Cluster 3; consisting of three sites, maize responded poorly to all amendments due to relatively high soil fertility (≥17 mg P kg−1). Profitability of using NPK amendments is limited to Cluster 1 and 2 and the largest Value Cost Ratio (VCR) of 3.1 is attainable only when soil available P is below 4.72 mg kg−1. These variable responses indicate the need for developing site-specific fertilizer recommendations for improved maize production and profitability of fertilizer use in poorly responsive soils.
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Claims 6
Claim · model-written summary
Maize responded to all amendments at nine sites in cluster 1.
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cluster 1, comprising of nine sites, maize responded to all amendments”
Claim · model-written summary
Maize responded only to the inorganic N, P, K, Ca, Zn and Cu amendment at six cluster 2 sites.
- Treatment
- N, P, K, Ca, Zn and Cu (inorganic)e0
- Outcome
- maize respondede0
- Direction
- respondede0
- Value
- six sitese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cluster 2, holding six sites, maize responded only to one amendment, N, P, K, Ca, Zn and Cu (inorganic)”
Claim · model-written summary
Maize responded poorly to all amendments at three cluster 3 sites with relatively high soil fertility.
- Treatment
- all amendmentse0
- Outcome
- maize respondede0
- Direction
- poorlye0
- Value
- three sitese0
- Qualifier
- relatively high soil fertility (≥17 mg P kg−1)e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cluster 3; consisting of three sites, maize responded poorly to all amendments due to relatively high soil fertility (≥17 mg P kg−1)”
Claim · model-written summary
Profitability of NPK amendments was limited to clusters 1 and 2.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Profitability of using NPK amendments is limited to Cluster 1 and 2”
t0“Maize (Zea mays L.)”
Claim · model-written summary
The largest value cost ratio was 3.1 when soil available P was below 4.72 mg kg−1.
- Outcome
- Value Cost Ratio (VCR)e0
- Direction
- largeste0
- Value
- 3.1e0
- Qualifier
- soil available P is below 4.72 mg kg−1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the largest Value Cost Ratio (VCR) of 3.1 is attainable only when soil available P is below 4.72 mg kg−1”
t0“Maize (Zea mays L.)”
Claim · model-written summary
The authors call for site-specific fertilizer recommendations for maize production and profitability.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the need for developing site-specific fertilizer recommendations for improved maize production and profitability of fertilizer use in poorly responsive soils”
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