Extractable phosphorous accumulation due to fertilization in the irrigated and rainfed maize fields
Lukyamuzi, Ddembe Joseph
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Phosphorous remains one of the most essential nutrients required for optimum maize production. Its importance as a nutrient is mainly for proper establishment of plant roots. Farmers are using P fertilizers in various maize farming systems but the effect of P based fertilizer application on extractable P build up remains unknown. To monitor and provide evidence for extractable phosphorous accumulation due to P fertilization effects, a research study was conducted in two contrasting maize farming systems. Maize fields from an irrigation-based farming system of Mubuku irrigation scheme in Kasese district and maize fields from a rain-fed based farming system in Bwijanga sub county Ntooma parish within the village of Kyamarolere Masindi district were sampled. The maize fields sampled in the two farming systems were categorized into 3 categories;1) fields under fertilization for less than a year, 2) fields under fertilization for 2-5 years and 3) fields under fertilization for more than 5 years. The representative soil samples were collected and later tested in the laboratory for available phosphorous, soil texture, soil pH and soil organic matter. Soil test results indicated a significant extractable phosphorous buildup (P<0.001) in the irrigation-based farming system with the highest at 97.51 ppm. However, the highest P buildup occurred in maize fields under fertilization for less than a year to as high as 97.51 ppm followed by maize fields under fertilization for more than 5 years with the highest at 65.82ppm. The lowest P buildup occurred in maize fields under fertilization for 2-5 years. There was no significant extractable phosphorous buildup (P>0.05) in the rain-fed maize farming system as the highest buildup observed was 10.51ppm. However, the highest P buildup was observed in maize fields under fertilization for more than 5 years with an average of 4.4ppm. This was followed by maize fields under fertilization for less than a year with an average of 4.23ppm. The lowest P buildup was observed in maize fields under fertilization for 2-5 years with an average of 3.45 ppm. Maize fields in the irrigation-based farming system are highly sufficient in available phosphorous whereas maize fields in the rain-fed based farming system are deficient in available phosphorous. Maize farmers in Kasese need to take into consideration the accumulated phosphorous content in their soil phosphorous management strategies for the purpose of achieving fertilizer use efficiency, economic efficiency, optimum maize production and environmental conservation. Maize farmers in Masindi need to increase their soil phosphorous stocks to match the critical levels vital to achieve optimum maize production.