Under a Tropical Climate and in Sandy Soils, Bat Guano Mineralises Very Quickly, Behaving More like a Mineral Fertiliser than a Conventional Farmyard Manure

Abstract

In sub-Saharan Africa, soil fertility management must rely on local fertiliser resources since most smallholder farmers do not have access to industrial fertilisers. In Vilankulo, Mozambique, farmers have access to bat guano and biochar, albeit in small amounts, which makes it even more necessary to manage them correctly to maximise crop productivity. This study was carried out with irrigated maize (Zea mays L.) in a haplic Lixisol during the 2017/2018 and 2019 growing seasons. Nine treatments were established consisting of the application of 5 (G5) and 10 (G10) t ha−1 of guano at sowing, 5 (B5) and 10 (B10) t ha−1 of biochar at sowing, 5 [G5(-1)] and 10 [G10(-1)] t ha−1 of guano one month before sowing, 1 and 4 (B1G4) and 2 and 8 (B2G8) t ha−1 of biochar and guano, respectively, at sowing and an unfertilised control (C). Treatments G10 and B2G8 led to the highest maize yields (3.77 and 2.68 t ha−1 in 2018 and 5.05 and 5.17 t ha−1 in 2019, respectively), and were statistically higher than those of the control (1.35 and 1.63 kg ha−1, respectively). Apparent nitrogen recovery from bat guano was close to 100%, showing almost complete mineralisation during the maize growing season, due to its low carbon/nitrogen ratio and very favourable environmental conditions for mineralisation. Due to the fast release of nutrients, bringing forward the application of the organic amendment before sowing is not recommended, since it reduces nutrient use efficiency. Biochar did not significantly influence maize grain yield or contribute significantly to plant nutrition. To take advantage of its potential effect on some soil properties, its use in combination with other materials of greater fertilising value is recommended.

Intercropped Maize and Cowpea Increased the Land Equivalent Ratio and Enhanced Crop Access to More Nitrogen and Phosphorus Compared to Cultivation as Sole Crops

“…In the present study, the short duration of the experiments did not permit significant variations in the determined soil properties. Furthermore, sandy soils and tropical climates lead to rapid degradation of organic residues [62,63], also contributing to a reduced probability of observing significant differences in soil properties between the three treatments.…”

“…One of the main recognized benefits of including legumes in rotations is their contribution of N to the subsequent crops [64,65]. The contribution of cowpea to N supply for cabbage may have increased due to the cultivation in sandy soil and a tropical climate, where the rate of mineralization of organic residues is usually high [62,63]. Therefore, cowpea grown as a sole crop or in intercrop seems to be a good preceding crop for non-legume species, provided there is not too much time between the end of its cropping cycle and the beginning of the succeeding crop to reduce the risks of N loss to the environment.…”

Ground Management through Grazing in Rainfed Olive Orchards Provides High Olive Yields and Has Other Potential Benefits for Both the Soil and the Farmer

“…Given that N occurs in relatively high concentrations in soil organic matter, typically containing about 5% N [42], it is the nutrient that is usually released to plants in greater amounts during soil organic matter mineralization [52][53][54]. For other nutrients such as P and B, lower average values were also recorded in the Tillage treatment compared to the others, but without significant differences.…”

Effect of Bat Guano and Biochar on Okra Yield and Some Soil Properties

“…Organic amendments generally increase crop productivity, as they provide nutrients for plant uptake and improve general plant growth conditions by increasing the soil water holding capacity; aeration; and many other physical, chemical and biological soil properties [31,32]. Furthermore, in previous studies where bat guano were used, positive effects on soil properties and/or on variables related to plant growth and yield were reported [13][14][15]33]. In contrast, treatments receiving only biochar as a soil amendment did not increase the plant height or fruit yield compared with the control in these two short-term experiments.…”

“…Biochar can benefit long-term plant growth by improving soil properties [37,38]. However, in short-term assessments, the use of biochar alone without any other fertilizing materials often results in low yields that are usually no different from control treatments [33,[39][40][41].…”