Abstract
<p>Mismanagement of soil fertility is one of the major challenges for farmers in the Sahelian zone of Niger. This study, conducted in 2012 and 2013 in western part of Niger, aimed at examining the effects of combined Zai and Mulching techniques on soil fertility and millet productivity. The experimental design was a randomized Fischer block with four treatments (Zai, mulching, Zai + mulching and Control) and four replicates. In the Zai treatment, 200 g cattle manure was added per Zai hole (2.8 t/ha) and millet straw (2.0 t/ha) was spread in the mulching treatment. The control treatment did not receive cattle manure or millet straw. The measurements concerned grain and straw yield of millet (<em>Pennisetum glaucum </em>(L.) R. Br.) as well as physico-chemical soil characteristics. The results show that the Zai + mulching treatment improved soil fertility parameters and grain yield significantly. The content of available phosphorus and clay in the soil was doubled after two years. The soil organic carbon content had increased from 0.45 to 2.1 g kg<sup>-1</sup>. The cation exchange capacity and pH had increased by one compared to the control. The content of total nitrogen (0.1 to 0.2 g kg<sup>-1</sup>) and total potassium (8.6 to 57.8 mg kg<sup>-1</sup>) did not vary significantly between treatments. An increase of 250 kg ha<sup>-1</sup> grain of millet compared to the control was obtained. Concerning the straw yield, the highest values were obtained by Zai treatment in both years (855±216 kg ha<sup>-1 </sup>in 2012 and 843±313 kg ha<sup>-1</sup> in 2013) and Zai + mulching in 2013 (888±251 kg ha<sup>-1</sup>). The combination Zai + mulching improved the soil fertility and millet productivity and can be used to restore degraded soils.</p>
Highlights
In semi-arid West Africa, the total extent of severely degraded soils due to agricultural activities has been estimated to 1.1 million km2 (Vågen et al, 2005)
The Zaï + mulching treatment had a significantly higher content of clay and clay + fine silt compared to the other treatments, whereas the highest content of sand particles was found in the mulching treatment (Table 1)
Concerning soil pH, the values obtained by the Zaï + mulching (5.1±0.1) and Zaï treatments (5±0.1) were not significantly different from the control, but had increased by one unit compared to the initial control value
Summary
In semi-arid West Africa, the total extent of severely degraded soils due to agricultural activities has been estimated to 1.1 million km (Vågen et al, 2005). In the Sahel, partmost soils are sandy, acidic and have low contents of clay and organic matter (Bationo & Mokwunye, 1991), which are some of the conditions that lead to crusting (Pieri, 1989). These inherent constraints of soil fertility have been exacerbated by the mismanagement of agricultural land. Nutrient balances are negative for many cropping systems, indicating that nutrient inflows are less than outflows. The annual depletion of nutrients such as nitrogen and phosphorus, which are the most limiting nutrients, is higher than the annual requirement (Bationo et al, 2008)
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