Abstract
BackgroundCassava is a heavy feeder crop that can cause serious depletion to soil nutrient stocks. This research aimed to explore soil fertility status and nutrient supply capacity at different growth stages of cassava fields under combined application of organic manure and NPK fertilizers in two agroecologies of Zambia. Topsoil (0–20 cm) samples were collected from cassava fields treated with factorial combination of four levels of chicken manure (0, 1.4, 2.8, and 4.2 ton ha−1) and four levels of NPK (control, 50N-11P-41.5K, 100N-22P-83K, and 150N-33P-124.5P). The soils were sampled under the cassava canopy to determine soil pH, available phosphorus (AP), total nitrogen (TN), organic carbon (OC), cation exchange capacity (CEC), exchangeable bases and micronutrients (Fe, Cu, Mn, and Zn). The samples were collected before planting andafter establishment at 4, 8, and 12 months after planting (MAP).ResultsManure application significantly (p < 0.05) increased soil pH, while the application of mineral fertilizer reduced soil pH at all the plant growth stages. Similarly, manure application and their interaction with mineral fertilizer increased OC and TN levels, especially at harvest. By contrast, OC and TN decreased with the application of mineral fertilizer. AP levels increased following the application of both fertilizers. In addition, manure application significantly increased soil Zn content from 0.69 mg kg−1 in the control to 3.54 mg kg−1 for the highest level of manure at harvest. The interaction between manure and NPK significantly affected Fe and Mn content in the soil.ConclusionThe results revealed that sole chicken manure application or its combination with mineral fertilizer improves soil nutrient status of cassava fields in Zambian condition.
Highlights
More than half of the rural Africans directly depend on crops that are grown locally in their surroundings
Smallholder farmers in Sub-Saharan Africa (SSA) apply inadequate amounts of nutrients to their farms, which results in overuses of the soil nutrient stocks by plants leading to gradual soil nutrient depletion and eventual soil degradation (Ayoola and Makinde 2014)
In terms of nutrient supply capacity, the soils are very low in soil organic carbon (OC) (1.0–1.2%) and total nitrogen (TN) (0.05–0.06%), and extremely low in cation exchange capacity (CEC) (3–4 cmol+kg−1) and basic cations (Ca2+, Mg2+, K+and Na+)
Summary
More than half of the rural Africans directly depend on crops that are grown locally in their surroundings. As in many counties of SSA, cassava (Manihot esculenta Crantz) is one of the mainfood staples in Zambia (Biratu et al 2018; Ntawuruhunga et al 2013) It is an important income generating and food security crop in Africa (Carsky and Toukourou 2005). Cassava is Biratu et al Environ Syst Res (2019) 8:3 a heavy feeder crop that can cause serious soil degradation because of excess nutrient removal (Howeler 2011). It extracts huge amount of soil nutrients, mainly potassium, followed by nitrogen and phosphorus (Imas and John 2013; Pongsivapai et al 2016). The samples were collected before planting andafter establishment at 4, 8, and 12 months after planting (MAP)
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