Relating Crop Productivity to Soil Microbial Properties in Acid Soil Treated with Cattle Manure
2014
Lupwayi, Newton Z. | Benke, Mônica B. | Hao, Xiying | O’Donovan, John T. | Clayton, George W.
Cattle (Bos taurus) manure can be used to correct soil acidity, supply plant nutrients, and increase soil organic matter. It usually affects soil microbial properties and crop production, but the relationship between the two effects is not always demonstrated. In a 4-yr study in which barley (Hordeum vulgare L.) was rotated with canola (Brassica rapa L.) on an acid soil, we investigated the effects of cattle manure on soil microbial characteristics and related them to other soil properties and crop productivity. The treatments were: (i) Control (no treatments), (ii) nitrogen and phosphorus fertilizer applied annually (NP), (iii) Lime (applied once) + nitrogen and phosphorus applied annually (Lime+NP), (iv) fresh manure applied once at 80 t ha–¹ (Manure80), and (v) manure applied once at 160 t ha–¹ (Manure160). The treatment order in microbial biomass carbon (MBC) was: NP ≤ Control ≤ Lime+NP < Manure80 < Manure160. Manure160 increased MBC by 34 to 150% in bulk soil, and by 49 to 117% in crop rhizosphere. Microbial activity ranged from 10.80 to 27.55 µg CO₂–C m–² d–¹ and was in the order: Control = Lime+NP ≤ Manure160 ≤ NP ≤ Manure80. Bacterial community structures differed between manure treatments and non-manure treatments. There were positive correlations of soil microbial characteristics with soil nutrient contents or crop nutrient uptake, and negative correlations with soil Mn and Na. The positive correlations sometimes translated into positive correlations with crop yields, and they underscore the crucial role of soil microorganisms in nutrient cycling.
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