No abstract

On low-input smallholder farms of Kenyan upland landscapes, erosion of nutrient-rich topsoil strongly affects crop yields. Where maize (Zea mays) is intercropped on erosion-prone slopes, intercropping can potentially reduce soil erosion. The objective of this research was to quantify the contribution of crops and crop mixtures of different growth habits to erosion control and their influence on above-ground biomass and earthworm abundance as indicators of soil function in smallholder farming systems under a bimodal rainfall pattern in Western Kenya. The experiment involved five treatments, namely maize (Z. mays)/common bean (Phaseolus vulgaris) intercrop (maize intercrop), maize/common bean intercrop plus Calliandra (Calliandra calothyrsus) hedgerows and Calliandra mulch (Calliandra), sole Lablab (Lablab purpureus), sole Mucuna (Mucuna pruriens) and groundnut (Arachis hypogaea) intercropped with maize (during the short rains). The experiment was conducted over three consecutive cropping seasons and the cropping system had significant effects on soil loss, runoff, water infiltration, earthworm abundance and above-ground biomass and crop grain yield. The Calliandra treatment had the lowest runoff (11.6-17.2 mm ha −1 ) and soil erosion (31-446 kg ha −1 per season) in all the seasons, followed by the Mucuna treatment. Lablab was affected by disease and showed the highest soil erosion in the last two seasons. Infiltration was highest in Calliandra treatment, and earthworm abundance was higher under Mucuna and Calliandra treatments (229 and 165 earthworms per square metre, respectively) than under other crops. Our results suggest that including sole crops of herbaceous species such as Mucuna, or tree hedgerows with mixtures of maize and grain legumes has the potential to reduce runoff and soil erosion in smallholder farming. Additionally, these species provide a suitable habitat for earthworms which stabilise soil structure and macropores and thus potentially increase infiltration, further reducing soil erosion.

Effective agricultural planning requires up-to-date and spatial crop phenology and land use (LU) data for time-critical and location-specific extension, inputs or emergency aid. Usually, this information is most sparse where most needed, (sub)tropical smallholder-dominated landscapes. Our study enhances planning methods for food-security and climate change adaptation in rain-fed smallholder agriculture of South Central Ethiopia. In a case study covering 10,500 km 2 and four agroecological zones, we developed a phenologyoriented approach for dynamic classification of cropping systems using Google Earth Engine. Complementary datasets of MODIS Enhanced Vegetation Index were merged, increasing time resolution from 16 to 8 days. Derived pixel-and crop-specific seasonal time series at 250 m resolution reflected vegetation phenology. Random Forest was applied to classify agricultural LU types and cropping systems. Vegetation period onset, validated against farmers' sowing dates, was used to detect crop rotations and map drought risk for the years 2003-2018. Identified LU types were: single cropping (maize/haricot bean, wheat/barley), and double cropping (maize/other, maize/wheat). Overall accuracy for agricultural LU was 76-94%.We use open source data and online data processing. High temporal resolution phenology data allow identifying needs for agricultural inputs and emergency support "in real time", assess drought risk and monitor LU dynamics.

Soil conservation approaches and agroforestry systems can play an important role in controlling erosion from tropical hillside cropping systems. Experimental testing of their potential application domain and design, however, is costly and time consuming. We, therefore, tested the ability of the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model. The specific objectives of the study were: (i) to evaluate the WaNuLCAS model for predicting water induced erosion under different soil conservation strategies, (ii) to use the model for a better understanding of various soil conservation measures in controlling erosion, and (iii) to assess the magnitude and dynamics of key processes influencing the efficiency of soil conservation measures. A 3-year-data set (2003)(2004)(2005) from a field experiment from the Loei province in Northeast Thailand on the impact of soil conservation (Leucaena hedgerow, Jack bean relay cropping) under minimum tillage on runoff and soil loss was tested. Results indicated that WaNuLCAS was able to predict soil loss and runoff well at the test site; i.e. R 2 = 0.80 and 0.82, respectively. In the calibration procedure a sub data set was used, where adjusting crop development parameters was an important step for improving simulated soil loss (R 2 = 0.75) and runoff (R 2 = 0.89). Soil conservation measures such as Leucaena hedges were effective techniques to control runoff and soil loss. Implementing a dynamic soil structure module in combination with minimum tillage reduced runoff and soil loss via an increase in available macropores and hence drainage over time which improved simulation results. Relay cropping with Jack bean played an important role in the control treatment in reducing soil loss during the third year due to its additional soil cover and positive impact on soil fertility as suggested by the model. Hence, the WaNuLCAS model is a valuable tool to study and understand processes and to explore management options for improving tropical hillside cropping threatened by soil degradation.

In a tsunami event human casualties and infrastructure damage are determined predominantly by seaquake intensity and offshore properties. On land, wave energy is attenuated by gravitation (elevation) and friction (land cover). Tree belts have been promoted as "bioshields" against wave impact. However, given the lack of quantitative evidence of their performance in such extreme events, tree belts have been criticized for creating a false sense of security. This study used 180 transects perpendicular to over 100 km on the west coast of Aceh, Indonesia to analyze the influence of coastal vegetation, particularly cultivated trees, on the impact of the 2004 tsunami. Satellite imagery; land cover maps; land use characteristics; stem diameter, height, and planting density; and a literature review were used to develop a land cover roughness coefficient accounting for the resistance offered by different land uses to the wave advance. Applying a spatial generalized linear mixed model, we found that while distance to coast was the dominant determinant of impact (casualties and infrastructure damage), the existing coastal vegetation in front of settlements also significantly reduced casualties by an average of 5%. In contrast, dense vegetation behind villages endangered human lives and increased structural damage. Debris carried by the backwash may have contributed to these dissimilar effects of land cover. For sustainable and effective coastal risk management, location of settlements is essential, while the protective potential of coastal vegetation, as determined by its spatial arrangement, should be regarded as an important livelihood provider rather than just as a bioshield. Indo-Australian and southeastern Eurasian tectonic plates 150 km off the coast of west Aceh, Indonesia, triggered one of the largest seismic events in the last four decades (1). The seaquake generated a tsunami with disastrous consequences in the region.Soon after the 2004 event, the possible effects of coastal vegetation regarding the impact caused by tsunamis (mitigating or aggravating) were researched into, especially under scenarios with initial water heights below 10 m (2-5). In Sri Lanka and India, coastal communities located behind tree cover were reported to be less affected than those directly exposed to the sea (2, 3, 6). Parameters such as stem diameter and height as well as a "bioshield" width were identified as key vegetation characteristics with a bearing on impact mitigation (6). However, several studies advocating bioshields have been criticized for lacking empirical evidence to support the protective function of vegetation, some even suggesting that bioshields may give a false sense of security to coastal populations (7-10). The role of vegetation in tsunami impact mitigation still remains a controversial issue (11-13). In the coastal regions of western Aceh in 2004, the potential for mitigating tsunami impacts appeared limited as a result of the massive energy released by waves with heights exceeding 20 m (13). Mangroves along this...