Soil amendment with agro‐industrial byproducts: molecular‐chemical compositions and effects on soil biochemical activities and phosphorus fractions

Environmental pollution by agro‐industrial byproducts in developing countries can be alleviated by recycling into soils. However, little is known about their chemical composition and impact on soil fertility. Therefore, the objectives of the present study were (1) to characterize the molecular‐chemical composition of dry (COD) and wet (COW) coffee, sisal (SIS), barley malt of brewery (BEB), and sugarcane processing (FIC) byproducts, and filter cakes of linseed (LIC) and niger seed (NIC) and (2) to evaluate their effects on respiration, pH, enzyme activities, and P fractions of a tropical soil. The agro‐industrial byproducts significantly differed in their concentrations of plant nutrients and organic‐matter compositions. The highest proportions of lipids, phenols + lignin monomers, and alkylaromatics were observed in COD, N‐containing compounds in COW, sterols in FIC, peptides in LIC, suberin in SIS, and fatty acid in COW and FIC. The application of the byproducts at the rate of 40 kg P ha^–1 (1.1 to 13.2 g C [kg soil]^–1) significantly (p < 0.05) increased the rate and cumulative soil respiration, soil pH, acid phosphatase and urease activities, and labile inorganic P over the control treatment. Ranking the qualities of the agro‐industrial byproducts for soil amendment based on their composition and effects on soil properties revealed the order NIC > LIC > BEB > COW > SIS > FIC > COD.     

Possible New Genes for Resistance to Powdery Mildew, Septoria Glume Blotch and Leaf Rust of Wheat

An Ethiopian wheat collection consisting of 293 tetraploid and hexaploid entries was investigated for resistance to powdery mildew, Septoria glume blotch, and leaf rust with the aim of finding probable new genes for resistance to these diseases. Seedlings were screened with isolates of these diseases in the greenhouse or growth chamber. The material was also scored for field resistance to powdery mildew after the fifth leaf stale. The diversity of the reaction types to powdery mildew and Septoria glume blotch was estimated by the Shannon-Weaver diversity index. Thirty-nine entries (13%) of the collection were resistant to moderately resistant co the mildew isolates, 14S-77 and 46—77, that had: a combined virulence spectrum effective against nine identified genes for resistance to powdery mildew. One hundred and et till TV-tour entries (63 %) of the collection showed field resistance to mildew. One hundred and eighty-one entries (62 %) of the collection were at least moderately resistant in an aggressive isolate of Sartorial nodorum. Resistance to a race of leaf rust was detected in one hundred and sixty-eight entries or 58.% of the collection. Generally, resistance to these diseases is concentrated in Central and Southern Ethiopia. The different reaction types of the resistant entries to these diseases and the high estimates of diversity for reaction types indicated the presence of many different probable new genes and genetic backgrounds for resistance to these diseases.     

Evaluation of agro-industrial by-products as nutrient source for plant growth

Nutrient leaching from dry (COD) and wet (COW) coffee, sisal (SIS), brewery barley malt (BEB) and sugar cane (FIC) by-products, and linseed (LIC) and niger seed cakes (NIC), and uptake by maize were studied in a pot experiment with tropical Alfisol. After three months, soils were leached to recover labile plant nutrients, and root and shoot biomass was harvested. The leachate from FIC-amended soil had the highest concentration of inorganic P (0.90 μmol L^?1), whereas the highest concentrations of potassium (K) (48,088 μmol L^?1) and calcium (2566 μmol L^?1) were determined in leachates from COD and BEB treatments, respectively. The amendments significantly increased K uptake by maize proportional to the amount of K applied, but the effects for other plant nutrients were small. The results indicated that pre-decomposition of agro-industrial by-products may increase the nutrient release in tropical soils.     

How does the Hedley sequential phosphorus fractionation reflect impacts of land use and management on soil phosphorus: A review

The Hedley sequential‐phosphorus (P)‐fractionation method has been used in many countries to study the effects of land‐use and management systems on soil P. Many data sets have been obtained but collectively never have been considered or to goal topic reviewed. Therefore, the objectives of this review were to compile and systematically evaluate these data. The data generated over many years were grouped into temperate, and subtropical and tropical soils of different land use and duration of soil‐management studies. In natural ecosystems, vegetation types and composition and percent of vegetation covers substantially affected all P fractions with pronounced impacts on the labile and moderately labile P. In short‐term studies (≤ 10 y), changes in the labile and moderately labile inorganic P (P_i) fractions were detected when more P (e.g., by factor 5) was applied than commonly recommended for agricultural crops. However, without P application the changes in all P fractions were subtle in temperate soils, but declines were significant in labile and moderately labile P in subtropical and tropical soils. In both temperate and tropical climates, medium (10–25 y) and long‐term (>25 y) cultivation without P application depleted all P fractions, whereas most of P fractions increased with continuous P application, regardless of the amount and source of P. Synthesis of data resulted in multiple‐regression functions which described differences in labile and moderately labile P fractions as function of differences in amount of P application and duration of the experiments. Moreover, the correlation analysis also showed strong association among most of the P fractions. Current limitations in data interpretation of Hedley fractionation can be overcome by the application of ³¹P nuclear–magnetic resonance (NMR) and X‐ray absorption near‐edge fine‐structure (XANES) spectroscopy.     

Patterns of Diversity of Ethiopian Wheats (Triticum spp.) and a Gene Center for Quality Breeding

A collection consisting of 293 entries of tetraploid and hexaploid Ethiopian wheat was investigated for diversity of endosperm texture, seed color, kernel texture, flour color, gluten quality, seed size, and protein content. All characters, except gluten quality, showed high levels of diversity- Significant differences in protein content and gluten quality occurred among districts, and among provinces. Regional differences were also observed for seed size and flour color. The average estimate of diversity of these characters for Ethiopia was high (H?= 0.77). Some of the characters showed clinal variations, and others, localized concentrations. Entries with combinations of good quality characters were observed, and their possible use as source materials in wheat breeding is discussed. A gene center for quality breeding was identified in Southern Ethiopia, and the participation of centers of diversity in the evaluation and utilization of genetic resources is considered as a very important tool in genetic conservation.