Organic farming practices increase weed density and diversity over conventional practices: A meta-analysis.

Population growth and climate change challenge our food and farming systems and provide arguments for an increased intensification of agriculture. Organic farming has been seen as a promising option due to its eco-friendly approaches during production. However, weeds are regarded as the major hindrance to effective crop production which varies depending on the type of crop and spacing. Their presence leads to reduced yield, increase in harvest cost and lower the qualities of some produce. Thus, weed management is a key priority for successful crop production. Therefore, we conducted a meta-analysis from published studies to quantify possible differences on weed density, diversity and evenness in organic and conventional farming systems and best intervention for weed management in organic farming system. Data included were obtained from 32 studies where 31 studies with 410 observations were obtained for weed density, 15 studies with 168 observations for diversity, and 5 studies with 104 observations for evenness. Standard deviation of mean was obtained from the studies, log transformed using natural logarithms and the effect size pooled using standardized mean difference (SMD). Publication bias was determined through funnel plot. Results showed that organic farming has significant higher weed density (P < 0.01), diversity (P = 0.01), and evenness (P < 0.05) compared to conventional farming. Despite so, diversified crop rotation has been proved to reduce weed density in organic farming by up to 49 % while maize-bean intercropping decrease densities of Amaranthus ssp, Cyperus ssp and Cammelina ssp compared with monocropping. Use of mulch after one hand weeding was found to control up to 98 % of weeds and use of cover crop between 24 % and 85 % depending on the type of the cover crop. The study results show that organic farming encourages high weed density, diversity and evenness but use of the integrated approaches can help to maintain weed density at a manageable level.

Surface runoff and soil erosion from Nitisols and Ferralsols as influenced by different soil organic carbon levels under simulated rainfall conditions.

Soil erosion poses a challenge to the environment and the sustainable use of natural resources, particularly in relation to agricultural production. The study aimed to assess the influence of different soil organic carbon (SOC) levels on runoff and soil erosion under varying levels of rainfall intensity. The study was conducted in pre-selected farmers' fields representing low, moderate and adequate SOC levels in Nitisols and Ferralsols. Two parallel experiments were set up in each type of soil using a split-plot layout arranged in Randomized Complete Block Design. The main plots were the different soil organic carbon levels while the sub-plots were the different simulated rainfall intensities. Rainfall simulation was then conducted to determine runoff and sediment losses on each soil type. The simulation was done using a land type sprinkler nozzle rainfall simulator (460 788 type) in an experimental plot of 1 m2, fenced with corrugated iron sheets with a small opening left for runoff collection. Runoff and sediment losses were determined from the volume collected in the jar. The data was subjected to analysis of variance and significant mean differences were determined using Tukey's Honest Test at a 95% confidence level. Pearson correlation was applied to assess the relationship between runoff volume and sediment loss. The results showed that Ferralsols recorded significantly higher runoff and sediment losses compared to Nitisols, by 60.27% and 53.14% respectively. However, adequate SOC level portrayed a significant effect in reducing erosion in both soil types, where it reduced runoff and sediment loss by 45.30% and 48.38% in Ferralsols and by 65.31% and 48.22% in Nitisols, respectively. In both soil types, runoff yield was positively correlated to rainfall intensity while sediment yield was inversely correlated with SOC levels. Therefore, the study recommends incorporation of organic matter to adequate levels in both soils, for reduced soil erosion.

Soil water use efficiency under integrated soil management practices in the drylands of Kenya.

Soil moisture scarcity and soil fertility decline in the drylands contribute to declining crop productivity. The possible synergistic effects of integrating soil & water conservation, and soil fertility management practices on soil moisture, and hence water use efficiency (WUE) in the drylands of Tharaka-Nithi County in Kenya was assessed. The experiment was laid in a three by three split plot arrangement, with four replications, for four cropping seasons. Minimum tillage with mulch, tied ridges, and conventional tillage formed the main plot factors. The sub-plot factors included animal manure plus fertilizer at 120, 60, and 30 N kg ha-1. There was significant improvement in soil moisture by 35 and 28% by minimum tillage with mulch and tied ridges, respectively, compared to conventional tillage. Manure plus fertilizer rates of 120 and 60 N kg ha-1 had significantly lower soil moisture by 12 and 10%, respectively than the 30 N kg ha-1 across the seasons. The WUE was significantly enhanced by 150 and 65% under minimum tillage with mulch and tied ridges, respectively, compared to conventional tillage. Compared with 30 N kg ha-1, the 120 N kg ha-1 and 60 kg ha-1 significantly enhanced the WUE by 66 and 25%, respectively. Across the seasons, the best treatment combination for improving WUE was minimum tillage with mulch at 120 N kg ha-1 rate of manure plus fertilizer.

Maize grain yield and grain zinc concentration response to zinc fertilization: A meta-analysis.

Zinc deficiency in agricultural soils is a current global agroecosystems challenge. Maize exhibits elevated susceptibility to Zn deficiency and low response to zinc fertilization. As a result, there are contradicting literature reports on the crop response to zinc fertilization. This meta-analysis synthesized the current evidence on maize response to zinc fertilization from different studies and highlighted the potential innovations to improve the crop response to zinc application. Systematic literature searches were conducted on the Web of Science and Google Scholar for peer-reviewed publications. From the selected publications, data extracted were maize grain yield and maize grain zinc concentration. The meta-analysis was conducted in R statistical environment using the metafor package. The ratio of means was the chosen effect size measure used. The assessment of effect size heterogeneity showed that the study effect sizes were significantly heterogeneous and also publication bias was evident. The analysis showed 17% and 25% maize grain yield and grain zinc concentration response to zinc fertilization. As a result, zinc fertilization was associated with yield increments of up to 1 t ha-1 and 7.19 mg kg-1 grain zinc concentration over the control (no zinc application). Despite the observed maize grain response to zinc application, the median concentration of grain Zn was below the 38 mg kg-1 recommended maize grain zinc concentration to combat human zinc deficiency (hidden hunger). As a result, potential innovations likely to achieve sufficient maize grain zinc content were highlighted including the use of nano-particulate zinc oxide, foliar zinc application, timing of zinc application, precision fertilization and zinc micro-dosing. Due to scanty literature on the progress of these innovations in maize, follow-up studies are recommended to evaluate their potential success in the agronomic bio-fortification of maize with zinc.

A quantitative appraisal of selected agroforestry studies in the Sub-Saharan Africa.

The multiple ecosystem services and livelihood assets development challenges facing the world, including climate change, land degradation, and high poverty levels, have necessitated cross-cutting solutions. Such includes agroforestry technologies, where trees are integrated with crop and pasture lands to yield multiple ecosystem goods and services. Though an ancient approach to land management, agroforestry faces a modern and urgent demand for expansion to counter ecosystems-livelihoods imbalances in most regions across the globe. This paper sought to synthesize the dynamics and characteristics of agroforestry technologies in sub-Saharan Africa by adopting the systematic review approach. Eighty-six (86) agroforestry studies were reviewed, analysing variables such as the dominant agroforestry technologies, production systems, types of studies, and ecosystem services generated by different agroforestry technologies. It established that majority of the agroforestry studies are multiple (undefined) in nature at 36%, have moderately changed over the years, the dominant agroforestry study type is journal articles (59%), and they are mostly scientific in nature (57%). Further, income generation was the dominant provisioning service (31%), greenhouse gas emission reduction was the main regulatory service (31%), and soil fertility management was the key support service. Tradeoffs associated with agroforestry technologies, including increased deforestation rates, tree-crops competition, increased pests and diseases, and potential food insecurity due to reduced crop production were also identified. Barriers to agroforestry such as insecure land tenure systems and inadequate research development are discussed. Pathways towards increased agroforestry technologies adoption, such as creating a conducive institutional and policy environment, as well as developing business support services for agroforestry-related goods and services were identified. The study reiterates the need for increased agroforestry technologies adoption to create the ecosystems-livelihoods balances, with sufficient measures to minimize the potential tradeoffs.

Communication factors influencing adoption of soil and water conservation technologies in the dry zones of Tharaka-Nithi County, Kenya.

Integrated soil fertility and soil water conservation technologies are possible solutions to the low per capita food production in Sub-Saharan Africa (SSA). Nonetheless, the rate of adoption of these technologies by smallholder farmers has stagnated over the years despite being recommended. This has been attributed to the existence of wide communication gaps among researchers, extension agents, and farmers. Therefore, this study aimed to assess the influence of communication factors on the adoption of the selected technologies among smallholder farmers in the drylands of Tharaka-Nithi County. We used a cross-sectional survey design and collected data using an interview schedule from 400 randomly selected farming households. Binary logistic regression was employed for data analysis. Results showed that accessibility of extension agents after introducing the technology significantly influenced the adoption of combined organic and inorganic fertilizers (p = 0.056), mulch (p = 0.051), and Zai pit (p = 0.058). Similarly, practical orientation significantly influenced the adoption of combined organic and inorganic fertilizers (p = 0.001), mulch (p = 0.010), and Zai pit (p = 0.003). Information repetition significantly influenced the adoption of combined organic and inorganic fertilizers, mulch, and Zai pit at p-value 0.003, 0.001, and 0.001, respectively. Training was essential for mulch and Zai pit technologies at (p = 0.030) and (p = 0.001) respectively, while farmer group membership significantly influenced adoption for combined organic and inorganic fertilizers (p = 0.045) and Zai pit (p = 0.057) technologies. Extension agents should increase their interactions with farmers after the introduction of technologies. Equally use of demonstrations should be encouraged during the dissemination of these technologies among the farmers as they enhance the chances of adoption of the technologies.

Gender-specific determinants of Zai technology use intensity for improved soil water management in the drylands of Upper Eastern Kenya.

Degraded landscapes and soil water stress are long-standing problems to smallholder agriculture in the drylands. Despite the important roles of zai technology in restoring degraded landscapes and improving agricultural productivity, the technology is yet to be adopted to its fullest extent. This can be attributed to gender-linked disparities in agricultural technology utilization. The study, therefore, sought to determine gender-specific determinants of zai technology choice and use-intensity. A multistage sampling technique was employed in randomly selecting 133 female-headed households and 267 male-headed households in Tharaka South sub-county. Quantitative data were collected in a cross-sectional survey using an interviewer-administered questionnaire. Using sex-disaggregated data, Chi-square and t-test statistic were employed to test the statistical significance of dummy and mean value of continuous variables, respectively. Gender specific determinants of zai technology choice and use-intensity were determined using the Heckman-two-step econometric model. The results revealed that, more women farmers (44%) were using zai technology as compared to men (38%). Among women farmers, total cultivated land, access to animal-drawn farm implements, and group membership had an influence on zai technology choice. For men, total cultivated land, group membership and access to extension services positively influenced choice of zai technology. With regard to zai technology use-intensity, total land cultivated, livestock densities, group membership and frequency of trainings on soil and water management were important determinants among women farmers. For men, zai technology use-intensity was determined by total cultivated land and farmers' perceptions on soil erosion. We recommend that, gender-sensitive farm-level policies oriented towards farmer socioeconomic profiles are important deliberations towards choice and intense application of soil and water conservation strategies such as the zai technology.

Socio-economic predictors, soil fertility knowledge domains and strategies for sustainable maize intensification in Embu County, Kenya.

Integrated Soil Fertility Management (ISFM) practices are widely recognized as crucial interventions but knowledge-intensive technologies for farmers in Sub-Saharan Africa (SSA). Very few studies have synthesized the knowledge gaps between small-holder practices and recommended ISFM packages. A farm survey was therefore carried out in Runyenjes sub-County of Embu to determine factors influencing the quality of ISFM knowledge considering inorganic fertilizer, organic manure, integrated soil inputs, and improved maize seeds. One hundred small-scale maize farmers were systematically sampled in Embu County, Kenya, using a cross-sectional survey design. The most significant factors shaping the quality of ISFM knowledge (p < 0.05) included gender, age, household size, land under maize, off-farm earnings, maize yield, members involved in farming, farming experience, education level, and farm size. Farmers recorded lower knowledge scores for technical ISFM themes including soil liming, soil testing, fertilizer types, fertilizer functions, curing of organic manure, compost manure management, crop spacing, combination ratios for integrated inputs, and the labor and cost-benefit implications of integrated inputs, revealing important ISFM knowledge gaps. High-quality knowledge of blended fertilizers and DAP use was associated with increased soil testing and soil liming knowledge, respectively. Multivariate analysis of ISFM knowledge items provided a high-quality understanding of the structure of ISFM knowledge among farmers in Embu County, which is useful in developing future ISFM dissemination strategies.