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Soil acidity with associated low nutrient availability is one of the major constraints to soybean production in southwestern Ethiopia. Integrated use of lime and acid-tolerant crops is believed to reduce soil acidity and improve crop production. The experiment was conducted in the field condition of Mettu, southwestern Ethiopia during the 2017/18 main cropping season. The experiment comprised fifteen soybean genotypes and two soil amendment (lime and unlimed) treatments arranged in a split-plot design with three replications. For each treatment, four rows were planted per plot; data related to growth, root, nodule, and yield of the crop were collected at a necessary stage for each. Liming and genotype interaction had significantly (P = 0.01) affected all parameters considered except for hundred seed weight and root volume and were affected only by the main effects of genotypes and liming. A significant reduction for most parameters was found on lime-untreated soil than treated soil. Though some genotypes showed higher performance for root, growth parameters, and yield components under unlimed soils; however, gave higher yield and yield components, when grown on lime-untreated with an average yield reduction of 13.7%, due to soil acidity. The maximum grain yield of (1943.93 kg ha-1) was obtained under lime treated acid soil from PI567046A genotype; while the lowest (510.49 kg ha-1) were recorded from SCS-1genotype under the lime untreated acid soil. Genotype BRS268 showed higher yield (1319.83 kg ha-1) under lime untreated acid soil than lime treated acid soil (1143.47 kg ha-1) and showed less reduction percentage for a number of the nodules, root weight, and number of seeds per plant; while PI567046A showed high reduction percentage for yield, biomass, number of pod and seed per plant. A high difference was observed among the soybean genotypes for soil acidity tolerance, which might be further exploited by breeders for the genetic improvement of soybean. Genotype BRS268 had performed better than other tested genotypes under increased soil acidity. selection would be effective to improve soybean genotypes performance on acid soils and identify low Phosphorus tolerant genotype that helps smallholder farmers optimize soybean productivity on acid soils in the study area. HAWASSA-04 variety is the most tolerant among the tested materials. However, further study is required by considering additional genotypes to reach a conclusive recommendation [ABSTRACT FROM AUTHOR]

Fertilization with suitable amendment in acidic soil is crucial to achieve long-term high crop yield without deteriorating soil health in intensive cropping system. We studied the chemical and biological properties of soil, soybean, and wheat yield after 47 years of long-term fertilization in an acidic Alfisol. Treatments were: unfertilized (control); recommended N dose (N); recommended N and P (NP); recommended N, P and K (NPK); NPK + hand weeding (NPK + HW); NPK + 10 Mg ha−1 farmyard manure (NPK + FYM) and NPK + 0.40 Mg ha−1 lime (NPK + lime). Long-term application of NPK + FYM significantly enhanced the soil cation exchange capacity (CEC), organic carbon, available NPK and microbial functions compared to NPK. Application of NPK + lime increased soil pH, dehydrogenase activity (DHA) and bacterial population by 15.7%, 38.8% and 145% respectively, over NPK. Continuous inorganic-P fertilizer application leads to substantial build-up of available-P in soil. Fertilization of FYM/lime with NPK recorded higher crops yield compared to NPK. Soil DHA, bacterial population and CEC were most influencing factors governing grain yield. Overall, long-term application of NPK with FYM/lime improved soil health and crop yield, but rate of inorganic-P input should be curtailed in an Alfisol. [ABSTRACT FROM AUTHOR]

There is a wide application of rhizobia inoculants to legume crops in Africa, irrespective of the soil acidity, though the latter limits the effectiveness of inoculants. Two trials were conducted in a controlled environment to determine suitable soil pH and impact of liming on soybean nodulation and nitrogen fixation to inform proper application of the rhizobia-inoculant technology on acid soils. In the first trial; soil, variety and inoculation had significant influence (p < 0.05) on weighed nodule effectiveness (WNE) and N fixation. Strongly acidic soils recorded low WNE and N fixation. In the second trial, WNE and N fixation significantly increased with co-application of lime and inoculation (p < 0.05). The results showed that soybean inoculation is effective in increasing nodulation and N fixation in moderate acidic soils, contrarily to strongly acidic soils. Interestingly, co-application of lime and inoculation has potential of increasing nodulation and N fixation in strongly acidic soils. The WNE is recommended as a robust formula to report nodule effectiveness, compared to the current percentage method. [ABSTRACT FROM AUTHOR]

Soil acidity limits crop growth and yield all over the world. Low grain yields is usually associated with poor soil fertility; however, little attention has been given to the nitrogen-based fertilizer use efficiency in soils managed with lime. Given the current scenario of uncertainties regarding the availability and prices of fertilizers, our study aimed to understand how maize intercropped with ruzigrass and soybean plants develop in long-term soils managed with lime rates, and what the fate of the 15N–labeled ammonium sulfate [(15NH 4) 2 SO 4 ] applied in the soil-plant system. The treatments consisted of four dolomitic lime rates applied to the soil surface [control, half the recommended lime rate (½ RLR), full recommended lime rate (1 RLR) and double the recommended lime rate (2 RLR)]. The higher lime rate (2 RLR) improved fertility, carbon and nitrogen stocks in the soil profile, and grain and/or stover production of maize, ruzigrass and soybean. As a consequence, maize and ruzigrass recovered a high amount of 15N-fertilizer. On the other hand, soybean recovered less 15N-fertilizer, regardless of treatment, but a greater amount was found in acidic soils. At the end of the maize and soybean growth cycles, our results showed that in 2 RLR-amended soil, the 15N unrecovered was 71% lower than control. Finally, our results suggested that the use of low lime rates (½ RLR) may increase the 15N losses potential to deep layers, whereas low amounts of 15N were found in the subsoil when higher lime rates were applied. Soil acidity management through higher lime rates leads, over time, to increased soil fertility, resulting in a favorable environment for plant growth and the use of nitrogen fertilizers. In this way, it is possible to obtain a more productive and less costly agricultural system, and with less potential to pollute the environment. • Soil fertility increases after long-term liming with higher lime rates. • The 15N-fertilizer recovery by crops is proportional to the soil fertility level. • Low lime rates increased the concentration of 15N-fertilizer in deep soil layers. • The higher 15N recovery leads to higher yields and lower N-fertilizer losses. [ABSTRACT FROM AUTHOR]

• Liming increases the amount of biological nitrogen fixation. • Liming provides higher soybean yields and a more positive N-balance. • Soil pH and Al saturation are key factors in biological nitrogen fixation. Soil acidity can impair biological N 2 fixation (BNF) and increase soybean (Glycine max L.) reliance on soil N to satisfy its plant N demand. This study aimed to evaluate the effect of liming, fertilization strategy, and grazing on: i) the N supplied via BNF process, ii) partial N-balance, and iii) soybean yield, in an integrated crop-livestock system under a non-tilled sandy and acidic Acrisol. Initial soil conditions were soil pH of 4.0 and Al saturation of 50%. Limestone was applied to rise soil pH to 6.0 and a control area was kept with the initial soil conditions. Soybean was grown in the summer and Italian ryegrass (as a cover crop or grazed by sheep) in the winter. Fertilization strategies consisted in applying P and K prior to soybean or ryegrass. Partial N-balance was calculated by the difference between N derived from BNF and N removed in soybean seeds. Contribution of N from the atmosphere to soybeans was on average 62 and 66% in plots without and with liming, respectively. The fixed-N was 27% greater under low soil acidity due to lime. Partial N-balance was positive in both treatments, but 57% greater in the limed- relative to the non-limed (+58 kg ha−1) soils, resulting in 11% soybean yield increase when lime was added. The most relevant soil chemical properties influencing N fixation were soil pH and Al saturation. Grazing and fertilization strategies had no effect on soil acidity properties, N supply, and soybean evaluations. Further research should explore the long-term effect of grazing, fertilization strategies, and liming. [ABSTRACT FROM AUTHOR]