Rain-fed Agricultural Areas Research Articles

Analysis of Maize Planting Mode and Simulation and Optimization of Ridging and Fertilization Components in Arid Area of Northwest China

The arid area of Northwest China belongs to the rain-fed agricultural area of the Loess Plateau, and water resources have become one of the important factors limiting agricultural development in this area. This study employed the AquaCrop model to predict the yield advantages and environmental adaptability of maize in Dingxi City from 2016 to 2020 under two cultivation practices: ridge tillage (100% film coverage with double ridge-furrow planting) and flat planting (81.8% film coverage with wide-film planting). The numerical simulation of the tillage and fertilization process of the double-ridge seedbed was carried out by EDEM, and the key components were tested by the Box–Behnken center combination test design principle to obtain the optimal parameter combination. The results showed that ridge planting was more suitable for agricultural planting in rain-fed arid areas in Northwest China. The simulation analysis of ridging and fertilization showed that the forward speed of the combined machine was 0.50 m/s, the rotation speed of the trough wheel of the fertilizer discharger was 39 rmp, and the rotary tillage depth was 150 mm. The qualified rate of seedbed tillage was 93.6%, and the qualified rate of fertilization was 92.1%. The research shows that the whole-film double ridge-furrow sowing technology of maize is more suitable for the rain-fed agricultural area in the arid area of Northwest China. The simulation results of the ridging fertilization device are consistent with the field experiment results. The research results provide a certain technical reference for the optimization of the whole-film double ridge-furrow sowing technology.

Exploring the Water-Soil-Crop Dynamic Process and Water Use Efficiency of Typical Irrigation Units in the Agro-Pastoral Ecotone of Northern China.

Groundwater resources serve as the primary source of water in the agro-pastoral ecotone of northern China, where scarcity of water resources constrains the development of agriculture and animal husbandry. As a typical rainfed agricultural area, the agro-pastoral ecotone in Inner Mongolia is entirely dependent on groundwater for agricultural irrigation. Due to the substantial groundwater consumption of irrigated farmland, groundwater levels have been progressively declining. To obtain a sustainable irrigation pattern that significantly conserves water, this study faces the challenge of unclear water transport relationships among water, soil, and crops, undefined water cycle mechanism in typical irrigation units, and water use efficiency, which was not assessed. Therefore, this paper, based on in situ experimental observations and daily meteorological data in 2022-2023, utilized the DSSAT model to explore the growth processes of potato, oat, alfalfa, and sunflower, the soil water dynamics, the water balance, and water use efficiency, analyzed over a typical irrigation area. The results indicated that the simulation accuracy of the DSSAT model was ARE < 10%, nRMSE/% < 10%, and R2 ≥ 0.85. The consumption of the soil moisture during the rapid growth stage for the potatoes, oats, alfalfa, and sunflower was 7-13% more than that during the other periods, and the yield was 67,170, 3345, 6529, and 4020 kg/ha, respectively. The soil evaporation of oat, potato, alfalfa, and sunflower accounted for 18-22%, 78-82%; 57-68%, and 32-43%, and transpiration accounted for 40-44%, 56-60%, 45-47%, and 53-55% of ETa (333.8 mm-369.2 mm, 375.2 mm-414.2 mm, 415.7 mm-453.7 mm, and 355.0 mm-385.6 mm), respectively. It was advised that irrigation water could be appropriately reduced to decrease ineffective water consumption. The water use efficiency and irrigation water use efficiency for potatoes was at the maximum amount, ranging from 16.22 to 16.62 kg/m3 and 8.61 to 10.81 kg/m3, respectively, followed by alfalfa, sunflowers, and oats. For the perspective of water productivity, it was recommended that potatoes could be extensively cultivated, alfalfa planted appropriately, and oats and sunflowers planted less. The findings of this study provided a theoretical basis for efficient water resource use in the agro-pastoral ecotone of Northern China.

Analysis and Research on Production Effects of Full-Film Double Ridge-Furrow Mulching with Polyethylene Film and Biodegradable Film Based on AquaCrop

Water is an important factor limiting the development of arid rain-fed agriculture. Film mulching is an effective way to ensure yield in arid areas. However, whether biodegradable film can be used instead of polyethylene film for agricultural production in arid areas is a matter of contention. In this study, AquaCrop model simulation and field experiment were used to analyze the production effect of corn whole film double ridge furrow sowing technology covering polyethylene film (PM) and biodegradable film (BM) in Dingxi City from 2016 to 2020. The results showed that the AquaCrop simulation data have a high fitting with the field test data, and the model was suitable for simulating dry farming in Dingxi City. The best sowing time in Dingxi City is to select the average temperature to be stable at about 15 °C (around 15 April to 25 April each year), and the yield is the highest after sowing during this period. Although BM can achieve environmental protection and energy saving, it is weaker than PM in water storage and soil evaporation inhibition in arid areas. The average yield, aboveground biomass, water productivity, and harvest index of PM were 63.95%, 18.57%, 76.35%, and 38.22% higher than those of BM, respectively. In drought years, BM water stress on leaf expansion, induced stomatal closure, and premature senescence were 61%, 17%, and 9.5% higher than PM, respectively, and the stress time was 28.5 d, 5 d, and 26 d, respectively. The maximum canopy coverage and effective root zone water content were 24.5% and 30.49% lower, respectively. In the wet year, water stress under BM only had a certain effect on the leaf expansion of crops but had no effect on the induction of stomatal closure and premature senescence. The maximum canopy coverage and effective root zone water content were 13.56% and 31.35% lower, respectively. The above studies show that BM has a certain ability to store water and preserve moisture, but the parameters of PM are better than BM. Especially in dry years, the crop production efficiency of PM is more significant. It can be seen that in rain-fed agricultural areas with rainfall less than 500 mm, biodegradable film can not replace polyethylene film.

Assessment of Temperature of Ramgarh District, Jharkhand, India: A Case Study of Coalfield’s Temperature

Global interest in climate variability, especially annual temperature changes, necessitates an analysis of spatiotemporal meteorological dynamics, particularly in regions relying on rain-fed coal field agriculture areas. This study examines the impacts of temperature trends and climate change in Jharkhand's Ramgarh district, India. Six sub-divisions, such as Ramgarh, Gola, Chitarpur, Mandu, Patratu, and Dulmi, are under-examined, exploring long-term temperature changes from 1981 to 2022. Leveraging the Mann-Kendall test and Sen's slope Test, a 42-year data set analysis uncovers a decrease in average and maximum temperatures, contrasting an increasing minimum temperature trend. Applying Sen's slope for each temperature category Maximum, Minimum, and Average at Six sub-divisions of the Ramgarh district where Mandu has the highest increasing slope of 0.01 was observed in minimum temperature. However, Gola’s maximum and average temperature observed the highest decreasing slope among all stations. Similar patterns were found at other stations. Hence, our study suggests that additional attention should be given to the variability of temperature, and it is imperative to consider the increasing temperature trend to mitigate its effects on human well-being.

Research on green water components and potential evaluation framework based on MIKE SHE model – A case study in the Loess Plateau of China

Exponentially increasing water demand and increasingly uncertain hydrological conditions due to climate change (CC) and land use/cover change (LUCC) undoubtedly pose significant challenges to the sustainability of water systems in arid and semi-arid regions worldwide, and even more so in the rain-fed agricultural area of the Loess Plateau (LP) in China, where green water supports all ecological landscapes and most agriculture. Therefore, an accurate assessment of green water resources is crucial for regional development. This paper constructed a comprehensive framework for assessing green water resources based on the MIKE SHE model, defined a new concept of green water components (GWCs) that can be extracted based on existing studies, proposes the potential of green water (GWP), and present a research methodology. To validate this research framework, we applied it to a typical basin in the LP gully area of the Nanxiaohegou (NXHG) basin. The model was calibrated using runoff data from basin outlet stations to extract four GWCs: high-efficiency green water (GWH), low-efficiency green water (GWL), unused green water (GWU), ineffective green water (GWI). We then assessed the GWP of the basin and analyzed its trends, consistency, and dependence on changing environments. The assessment framework is simple and easy to use, providing valuable information for regional revegetation and basin water management, and is highly recommended for replication in other regions.

Evaporation effect of infiltration hole and its comparison with mulching

Reducing ineffective evaporation of soil water is an important way to relieve drought in semi-arid rainfed agricultural areas. An infiltration hole is a supplemental measure for slope rainwater harvesting measure and is commonly used in vegetation restoration and orchard management of slopes. However, the evaporation effects of infiltration holes are unclear. In this study, we determined the evaporation effects of infiltration holes under a high initial soil water content and compared the differences in inhibition of soil evaporation among infiltration holes, mulching, and their combination after a rainstorm event. The results showed that the infiltration holes at different depths increased soil daily evaporation in the first 26 days under the high initial soil water content, after which it decreased. Compared with the control, the average daily evaporation while covering the top surface and the hole (sidewall and bottom) decreased by 74.3% and 4.3%, respectively. After the rainstorm event, cumulative evaporation (97 days) significantly decreased by 42.0% and 34.0% under the infiltration hole compared to gravel mulching and branch mulching, respectively. Overall, the infiltration hole increased soil evaporation at the early stage. Soil water mainly evaporated through the top surface of the soil column rather than through the hole itself. In the long term after rainstorms, infiltration holes have better effects in inhibiting evaporation than mulching. Our findings determine the evaporation effects of infiltration holes in the process of harvesting rainwater to replenish soil water in semi-arid rainfed agricultural areas.

Longwan 5: A Semi-Leafless Sugar Snap Pea Cultivar Resistant to Powdery Mildew

Garden pea (Pisum sativum L.) is an important legume crop, which is widely planted in Yunnan-Guizhou Plateau and Sichuan Basin of southwest China. It has developed rapidly in spring planting agroecological zone in Northwest China in recent years. The major constraints to its cultivation are lodging and infection of powdery mildew. Breeding of high yielding cultivars resistant to powdery mildew is of great significance for the sustainability of pea production, because few local garden pea cultivars are resistant to the disease. Varietal diversification is needed to develop pea cultivars with resistance to lodging and powdery mildew. Breeding work was initiated to develop a high-yielding garden pea cultivar with medium maturity, double podding and resistance to powdery mildew. Longwan 5 (X9002) is high yielding, superior quality, multiple resistance, and climate resilient garden pea cultivar developed by hybridization between Shuanghua 101 and Baofeng 3. It is a semi-leafless pea variety with superiority over existing approved varieties Qizhen 76 and Xucai 1 in terms of green pod yield, medium maturity, and double podding. Longwan 5 gave a significantly higher average green pod yield (12,376 kg/ha) than check varieties Qizhen 76 (11,132 kg/ha) and Xucai 1 (11,649 kg/ha) across five locations and three years, which was 11.2% and 6.3% higher than control varieties, respectively. This variety is tolerant to lodging, powdery mildew disease, and wide climate resilient for spring cultivation as well as for autumn cultivation in irrigated conditions or rain-fed agricultural areas with annual precipitation of 450–650 mm in China. Cultivation of this variety on large scale will surely increase the production of peas in China and will also prove beneficial for farmers increasing their income.

Is biodegradable film an alternative to polyethylene plastic film for improving maize productivity in rainfed agricultural areas? — Evidence from field experiments

Due to increasing concerns regarding plastic pollution throughout the world, biodegradable mulch is considered a promising alternative to polyethylene film and its suitability has been verified in some crops. However, it is unclear whether the long-term continuous use of biodegradable mulch as a substitute for polyethylene film is sustainable in rainfed agricultural areas, and whether its effect is consistent under different climatic conditions. Therefore, we conducted 7-year (2013–2019) and 4-year (2015–2018) field experiments in two regions with different precipitation levels (semiarid and semi-humid regions) on the Loess Plateau in China. We compared the effects of polyethylene film mulching (PM), biodegradable film mulching (BM), and traditional flat planting without film mulching (TF) on the soil temperature, soil moisture, grain yield, crop water productivity (WPc), and economic benefit (EB). The results showed that compared with TF, the grain yields under BM and PM increased by 2.1–93.3% and 7.6–34.6%, respectively, WPc increased by 2.1–93.3% and 7.6–34.6%, and EB increased by –16.6–131.5% and –7.8–27.0%. The differences in these indexes under the two mulching methods mainly occurred in the dry years with less precipitation in the semiarid region, whereas there were no significant differences in the grain yield, WPc, and EB under BM and PM in the semi-humid region. Therefore, the decision regarding whether BM can replace PM to improve maize productivity is significantly affected by the annual precipitation in rainfed areas. Furthermore, the univariate quadratic equation model was used to simulate that BM can obtain a higher crop yield and EB than PM when the precipitation is more than 600 mm and less than 800 mm, so as to achieve a win–win situation with continuous yield and income increases, and environmental friendliness in the Loess Plateau of China. However, the yield increase effect of plastic film mulching is also related to crop types, mulch types and farming practices except for climate. In addition, reducing the production cost will still be important for encouraging farmers to use biodegradable film instead of polyethylene film.

Soil bacterial community characteristics and ecological function prediction of alfalfa and crop rotation systems in the Loess Plateau, Northwest China

In order to understand the effects of lucerne cropping rotation on the bacterial community of loess soil, a long-term field experiment was conducted in rain-fed agricultural area of Loess Plateau. The cropping systems included continuous lucerne (Medicago sativa, LC), lucerne removed and rotated with spring wheat (Triticum aestivum, LFW), lucerne removed and rotated with corn (Zea mays, LFC), lucerne removed and rotated with potato (Solanum tuberosum, LP), and lucerne removed and rotated with continuous millet (Panicum miliaceum, LM). Based on 16S rRNA high-throughput sequencing technology, we investigated soil bacterial community structure and diversity in different cropping systems, and predicted ecological function using PICRUSt method. The results showed that the dominant phyla of loess soil bacteria were Actinomycetes (20.3%-32.0%), Proteobacteria (19.2%-23.0%), Acidobacteria (12.4%-14.2%) and Chloroflexus (11.0%-12.7%). The dominant genus was Bacillus (1.9%) in lucerne-corn system and Pseudarthrobacter (2.5%) in other treatments. Rotation with annual crops decreased the relative abundance of Actinobacteria and increased that of Chloroflexi and Firmicutes. Redundancy analysis showed that the main soil factors driving soil bacterial community structure were nitrate, ammonium, and total nitrogen. PICRUSt function prediction results showed that metabolism (78.6%-79.1%) was the main function of soil bacterial communities in loess soil. Rotation with continued annual crops significantly decreased the abundance of soil bacterial carbohydrate metabolism functional genes, and significantly increased the abundance of functional genes for soil bacterial cofactors and vitamin metabolism, neurodegenerative diseases, and immune system. In conclusion, lucerne removed and rotated with continuous annual crops changed soil bacterial community structure and ecological functions. This study provided theoretical reference to explore succession characteristics of soil bacteria and to select succeeding crops for alfalfa in loess soil.

Statistical verification of 16-day rainfall forecast for a farmers advisory service in Pakistan

Rainfall forecast is useful for farmers to avoid expensive irrigation decisions both in rain-fed and irrigated agricultural areas. In developing countries, farmers have limited knowledge of weather forecast information sources and access to technology such as the internet and smartphones to make use of these forecasts. This paper presents a case of developing Farmers Advisory Service (FAS) in Pakistan that is based on rainfall forecast data. The analysis emphasizes on statistical verification of 16-day rainfall forecast data from a global weather forecast model (Global Forecast System). In-situ data from 15 observatories maintained by Pakistan Meteorological Department in Khyber Pakhtunkhwa province has been considered for verification. Scores of various indicators are calculated for the rainfall forecast ranging from simple forecasts of dichotomous outcomes to forecasts of a continuous variable. A sensitivity analysis is also performed to understand how scores of dichotomous indicators vary by changing the threshold to define a rainfall event and forecast lead time interval. The quality of forecast varies across the stations based on the selected skill scores. The findings of verification, sensitivity analysis, and attributes of FAS provide insight into the process of developing a decision support service for the farmers based on the global weather forecast data.

Assessment of smallholders’ vulnerability to drought based on household-scale planting strategies and adaptability: A survey study of Xinghe County

The increase of the frequency, scope and intensity of drought has a great impact on agricultural production under the climate change. Smallholders are the most direct victims of drought. This paper focused on smallholders' planting strategies and family-scale indicators from the micro perspective and constructed a framework for smallholders' drought vulnerability assessment in semiarid rain-fed agricultural areas. The results show that: (1) There are significant spatial variations in smallholders' drought adaptability and the affected by drought, which may be related to the fragmentation of smallholders' cultivated land in different regions. (2) The drought vulnerability of smallholders also has obvious differences between north and south in Xinghe County. There are several obvious vulnerability hot spots in the south, especially in Datong Yao and Dianzi. The vulnerability index of smallholders in these spots may more than 0.7. (3) The effective irrigation area may be the best factor to explain the spatial variations of smallholders' drought vulnerability. Its interaction with slope can explain more than 20% of the vulnerability difference, which is significant at 0.05 level. This study is expected to enrich the evaluation dimensions of smallholders’ drought vulnerability assessment in arid and semiarid areas, reduce the risk of drought losses of smallholders, and improve the level of regional risk governance.

Applications of CRISPR/Cas9 as New Strategies for Short Breeding to Drought Gene in Rice.

Recent unpredictable climate change is the main reason for the decline in rice yield. In particular, drought stress is a major constraint in reducing yield and quality for rice at rainfed agriculture areas, such as Asia and South America. CRISPR/Cas9 provides an effective solution for gene function study and molecular breeding due to specific editing of targeted genome sequences. In addition, CRISPR/Cas9 application can significantly reduce the time required to develop new cultivars with improved traits compared to conventional complex and time-consuming breeding. Here, drought-induced gene Oryza sativa Senescence-associated protein (OsSAP) was edited by CRISPR/Cas9. To investigate the possible role of OsSAP in drought stress, genome-editing plants were subjected to drought stress until the soil moisture content reached 20%, and the reactive oxygen species (ROS) scavenging efficiency of genome-editing plants were decreased. When the genome-editing plants were subjected to drought stress, survival rate, shoot length, root length, content of chlorophyll number of tiller, and 1,000-grain weight decreased, and more H2O2 and O2− were detected in leaves. In addition, expression levels of several critical stress-related transcription factors were decreased in the OsSAP genome-editing plant. These results suggest that OsSAP function as a positive regulator during drought stress response in rice. We analyzed the expression of OsSAP and Cas9 in T0 and T1 plants as well as T2 seeds. As the course of generation advancement progressed, Cas9 expression remained stable or weakened but the OsSAP expression was continuously removed from the T0 plant. The coefficient of variation (CV) in both T1 plants and T2 seeds was lower than 5%. Overall, our results suggest that CRISPR/Cas9 could be a novel and important tool for efficiently generating specific and inheritable targeted genome editing in rice, with short breeding cycles.

A Deep Learning Approach to Mapping Irrigation Using Landsat: IrrMapper U-Net

Accurate maps of irrigation are essential for understanding and managing water resources. We present a new method of mapping irrigation based on an ensemble of convolutional neural networks that use reflectance information from Landsat imagery to classify irrigated pixels. The methodology does not rely on extensive feature engineering and does not condition the classification with land use information from existing geospatial datasets. The ensemble does not need exhaustive hyperparameter tuning and the analysis pipeline is lightweight enough to be implemented on a personal computer. Furthermore, the proposed methodology provides an estimate of the uncertainty associated with classification. We evaluated our methodology and the resulting irrigation maps using a highly accurate novel spatially-explicit ground truth data set, using county-scale USDA surveys of irrigation extent, and using cadastral surveys. We demonstrate the accuracy of the method by mapping irrigation over the state of Montana from years 2000-2019. We found that our method outperforms other methods that use satellite remote sensing information in terms of overall accuracy and precision. We found that our method agrees better statewide with the USDA National Agricultural Statistics Survey estimates of irrigated area compared to other methods, and has far fewer errors of commission in rainfed agriculture areas. This methodology has the potential to be applied across the entire United States and for the complete Landsat record.

Ridge–furrow rainfall harvesting system helps to improve stability, benefits and precipitation utilization efficiency of maize production in Loess Plateau region of China

The ridge–furrow rainfall harvesting (RFRH) system is considered an effective strategy for improving crop productivity and it has been adopted increasingly in the arid and semiarid rainfed agricultural areas of China. However, how RFRH performs at improving the crop productivity and the economic benefits of long-term implementation are not known in different counties and conditions in the Loess Plateau region. Therefore, RFRH and traditional planting method (CK) experiments were carried out by us under five different hydrothermal conditions in the Loess Plateau for many years. The denitrification–decomposition (DNDC) model was corrected and verified by field test data. Then, the performance of RFRH and CK in time (from 1990 to 2019, three test points) and space (387 counties, 112,000 km−2 grain crop planting area) was simulated. The results showed that from 1990 to 2019, the maize yield was 9200–11,395 kg ha–1 under RFRH and 1433–11,326 kg ha–1 under CK. The interannual variation in the maize yield was small under RFRH and it significantly improved the maize yield in dry years (87.0% higher than CK). In addition, RFRH effectively stabilized and improved the maize biomass (increased by 26.9%), harvest index (increased by 24.3%), and economic benefits (increased by 63.4%). In the whole Loess Plateau region, compared with CK, the average grain yield under RFRH increased by 86% and the average net income increased by 133%. The capacity of RFRH to increase the economic benefits in the Loess Plateau regions followed the order of: northwest region > northeast region > southwest region > southeast region. RFRH can improve and stabilize the maize yield, but also enhance the economic benefits of maize production in this region. Therefore, RFRH can be used as an important technique for coping with years when different amounts of precipitation occur in the Loess Plateau region, but especially in the northwest where the precipitation is limited.

Relationship between Drought and Precipitation Heterogeneity: An Analysis across Rain-Fed Agricultural Regions in Eastern Gansu, China

Based on daily meteorological data from 55 meteorological stations in eastern Gansu from 1960 to 2017, the characteristics of the drought process and precipitation heterogeneity were analyzed, and the relationship between drought and precipitation heterogeneity was evaluated. Results showed that there were 1–3 drought processes in the study area every year. Drought processes in the eastern and north-central regions were more frequent than those in other regions. Droughts were mainly manifested as intra-seasonal droughts, especially across the spring and summer. PCD (Precipitation Concentration Degree, the concentration degree of the precipitation at a certain time) ranged from 0.2 to 0.7 in the area. PCD increased in spring and autumn but decreased in summer and winter for most regions from 1960 to 2017. PCP (Precipitation Concentration Period, the shortest time which the precipitation was concentrated in) was from late April to early May in spring, mid-to-late July in summer, mid-September in autumn, and late January in winter. In the last 58 years, PCP has remained consistent in most regions, varying by approximately 10 days. In addition to insignificant changes in winter, the days with light and moderate rain presented a declining trend, especially in summer and autumn. The larger the PCD, the fewer the days with light and moderate rain, and the stronger the drought intensity. However, in the east-central region, the larger the PCD in autumn, the weaker was the drought intensity. This difference is related to the PCP and the evapotranspiration. Additionally, the later the PCP, the stronger was the drought intensity, particularly in summer and autumn. When PCD was ≥0.5 in spring and ≥0.4 in summer, the PCP was after May and August in spring and summer, respectively. Droughts appeared in 28–56% of periods when seasonal precipitation was above normal. When PCD was ≥0.5 in autumn and PCP was in early and middle September, droughts appeared in 7% of periods when precipitation was above normal. Our results show that although less precipitation is the leading influencing factor of drought in the dry rain-fed agricultural areas, the influence of precipitation heterogeneity should be also considered for the prediction and diagnosis of seasonal drought.

Land use mosaics in Mediterranean rainfed agricultural areas as an indicator of collective crop successions: Insights from a land use time series study conducted in Cap Bon, Tunisia

CONTEXTIn cultivated landscapes, land use patterns related to the diversity of crops, their spatial arrangement into patches and their succession over several years influence many biophysical processes and the production of ecosystem services and disservices. Understanding the determinants of these patterns is a prerequisite for the development of acceptable alternative land use patterns. Most studies deem crop distribution patterns at the landscape level to be the result of individual allocations of crop successions to fields designed at the farm level. However, in some parts of the world, there are collective crop successions that apply to groups of adjacent fields on different farms. OBJECTIVEThe objective of this study was to examine the extent to which the spatiotemporal distribution of crops at the landscape scale relates to collective crop successions. METHODSThe study was based on a Mediterranean rainfed agricultural landscape (67.7 km2) located in northeastern Tunisia, in which collective successions respond to constraints related to agricultural land fragmentation. Combined with field mapping, remotely sensed land use time series were used to identify three-year crop sequences, classify them into crop succession types and identify clusters of adjacent fields with the same type of crop succession. We assumed that such a cluster was the result of a collective succession if the determinants of the individual crop succession locations did not explain its size (expressed in the number of fields). We related such determinants to the characteristics of the fields and their land-use environment and defined them statistically. Then, we developed a spatial permutation test to distinguish clusters resulting only from the determinants of the individual crop succession locations from those resulting from collective succession. RESULTS AND CONCLUSIONSThe results show that the collective successions mainly comprised biennial successions (wheat sown alternately with legumes, spices or forage crops). These successions were synchronized between adjacent fields based on wheat cultivation; all fields in the same cluster had wheat in the same year. Collective successions were secondarily comprised of fodder-dominant successions. These collective successions involved approximately 40% of the fields and their total area in the study area. These fields belonged to different clusters ranging in size from two to 96 adjacent fields. SIGNIFICANCEThe developed approach is a tool for mapping the likely presence of collective successions and considering this factor in the definition of sustainable land use scenarios at the landscape level for better soil and water management.

Rainfall seasonality and timing: implications for cereal crop production in Ethiopia

Rainfall seasonality and timing are key climatic features affecting crop yield in rainfed agriculture (RFA). We evaluated the dynamics of temporal rainfall attributes – the strength of seasonality, the date of onset, cessation, and duration of the rainy season – over RFA areas across Ethiopia for the period 1981-2010 and explored their impacts on cereal crop production (including maize, teff, sorghum, wheat, barley, millet, oats and rice) between 1995 and 2010. First, we quantified the rainfall seasonality using an entropy-based seasonality index, defined the onset and cessation dates of rainy seasons, computed the rainy season duration, and analyzed their interannual variability and trends. Second, we correlated de-trended total cereal production during the Meher (i.e., long rainy) season (April to September) with the anomalies of the temporal rainfall attributes, and we used a univariate linear regression model to estimate the influence of changes in these attributes on crop production. We show that RFA areas in northern Ethiopia are characterized by a highly seasonal and unimodal rainfall regime. The southern parts of the RFA areas are characterized by less seasonal rainfall of bimodal and erratic nature. Cereal crop production during the Meher season, especially in teff and maize-dominated regions, is found to be correlated to both the onset (median ρ=-0.32 and -0.37, respectively) and duration (ρ=0.34 and 0.19) of the rainy season in the unimodal rainfall regime, whereas it is correlated with the rainfall seasonality (ρ=0.21) in regions with a bimodal rainfall. We estimate that on average over RFA areas, a late-onset and shorter rainy season lead to ∼1.5% and 1.1% crop production losses per pentad (5-day period), respectively.

Adoption of Soil Conservation Measures

Land degradation resulting from soil erosion is a major problem in rain-fed agricultural areas in India. This study analyses the key determinants of farmers’ decisions to adopt on-farm soil and water conservation (SWC) measures in the rain-fed watershed areas of Siddipet district in Telangana. Here, SWC measures have been undertaken by the government and NGOs at the sub-watershed/community level and by individual farmers at the farm level. The study is based on a primary survey of over 400 farmers conducted in January–March 2018. In addition to estimating the influence of biophysical and market access variables on farmers’ decisions to undertake SWC practices, the study includes a logistic model that found a complementarity between community and individual plot-level interventions to improve soil health. The findings also highlight the influence of conservation measures practised in the neighbourhood on farmers’ decisions to implement SWC measures.

Analysis of the Impact of Land Use Changes on Soil Erosion Intensity and Sediment Yield Using the IntErO Model in the Talar Watershed of Iran

Land use change is known as one of the main influencing factors on soil erosion and sediment production processes. The objective of the article is to study on how land use change impacts on soil erosion by using Intensity of Erosion and Outflow (IntErO) as a process-oriented soil erosion model. The study has been conducted under land use changes within the period of 1991–2014 in the Talar watershed located in northern Iran. The GIS environment was used to prepare the required maps including Digital Elevation Model (DEM), geology, land use, soil, and drainage network. The climatology data including average annual precipitation and air temperature as well as the volume of torrential rain were extracted from the data of meteorological stations located inside and around the study watershed. The results indicates that, within the period of 1991–2014, the forest area decreased by 12,478.04 ha (6%), while the other land uses including rainfed agriculture, rangeland, irrigated agriculture, and residential area increased by 7248.25, 4481.05, 476.00, and 273.95 ha, respectively. The estimated outflow with 100 year return interval was 432.14 m3 s−1 in 1991, which increased to 446.91 m3 s−1 in 2014. It can be concluded that the probability of larger and/or more frequent floods waves in the Talar River is expected to increase. In addition, the amount of production of erosion material (gross erosion) in the watershed increased from 1,918,186 to 2,183,558 m3 yr−1, and the real soil losses per year (sediment yield) of the watershed increased from 440,482.4 to 501,421.3 m3 yr−1. The results clearly emphasized how the lack of appropriate land management and planning leads to increase the maximum flow discharge and sediment yield of the watershed.

土地利用驱动的土壤性状变化影响微生物群落结构和功能

微生物在调节陆地生态系统地球化学循环过程中具有重要作用。土地利用方式改变显著影响土壤微生物群落结构和功能，但对土地利用驱动的土壤性状变化与微生物群落结构和功能关系的研究相对匮乏。依托长期定位监测试验（始于1984年），通过16S rRNA基因片段和ITS高通量测序，研究了土地利用方式（裸地、农田、草地）驱动的土壤碳氮变化对微生物群落结构和功能的影响。结果表明：对于细菌群落而言，裸地中α-多样性最高、其次是草地、农田中最低，农田和草地中细菌优势菌群变形菌（Proteobacteria）和放线菌门（Actinobacteria）相对丰度较裸地低4.5%、3.9%和5.5%、3.8%；对于真菌群落而言，裸地子囊菌门（Ascomycota）相对丰度最高、农田次之、草地最低；化能异养型、好氧化能异养型细菌相对丰度裸地显著高于农田和草地（P<0.05），而硝化型和好氧氨氧化型细菌裸地显著低于农田和草地（P<0.05）；腐生型真菌相对丰度大小排序为：裸地>农田>草地。细菌群落变化主要与土壤容重、全氮、矿质氮、C ： N比和微生物量碳有关，而真菌群落与土壤矿质氮有关。细菌和真菌功能菌群主要受土壤容重、土壤有机碳、土壤全氮、C ： N比和微生物量碳影响。因此，土壤容重、土壤全氮、土壤有机碳、C ： N比、微生物量碳、矿质氮差异可能是影响不同土地利用方式中微生物群落和功能变化的主要因素。;Microorganisms play an important role in regulating biogeochemical cycling in terrestrial ecosystems. Microbial functional structure and related processes are determined by the microbial community. Soil physiochemistry properties affect microbial community structure. Land uses affect soil properties and microbial communities, whereas most of the researches at home and abroad focus on the effect of different land uses on soil properties, and how effect of soil properties variations on microbial community and functional structure under land uses were unclear. In this study, land uses (i.e., bare-land, farmland, and grassland) were selected from the long-field experiment (established in 1984). The experimental plot is located at the Changwu National Field Scientific Observation and Research Station of Farmland Ecosystem in the highland and gully region of Shaanxi Province, which is a dry-farming and rain-fed agricultural area. Soil microbial community structure (16S rRNA and ITS), soil physiochemistry properties have been determined, such as soil bulk density (BD), soil organic carbon (SOC), soil total nitrogen (TN), soil microbial biomass carbon (SMBC), and soil mineral nitrogen (mineral N). We found that there was a significant difference in the relative abundance of microbial communities and functional structure under different land uses. Alpha diversity of soil bacterial community was the highest in bare-land, and followed by grassland and farmland. The relative abundance of Proteobacteria, Actinobacteria, and Ascomycota in the farmland (29.7%, 17.3%, 9.2%) and grassland (29.9%, 17.6%, 5.5%) were lower than in bare-land (31.1%, 18.3%, 27.0%). The relative abundance of chemoheterotrophy and aerobic chemoheterotrophy in the bare-land were significantly higher than those in the farmland and grassland, where nitrification and aerobic ammonia oxidation were significantly lower than those in the farmland and grassland (P<0.05). Saprotrophic fungi were the highest in bare-land, followed by farmland and grassland. Variation of bacterial community structure was influenced by BD, TN, mineral N, C:N ratio, and soil microbial biomass carbon (SMBC), while variation of fungal community structure was mainly influenced by mineral nitrogen. In addition, the functional community structure of both bacteria and fungi were mainly affected by BD, SOC, TN, C:N ratio, and SMBC. Specifically, Proteobacteria, Actinomycetes, Ascomycetes, and Basidiomycetes were more suitable to live in the farmland soil than in grassland. Chemical heterotrophic, aerobic chemical heterotrophic bacteria, and saprophytic fungi, which participated in soil carbon cycle, were mainly enriched in the farmland. Nitrification and aerobic ammonia oxidizing bacteria involved in the nitrogen cycle were mainly concentrated in the grassland. Therefore, the change of soil physiochemistry properties driven by land uses affected the community structure and function of microorganisms. In conclusion, variations of BD, TN, SOC, C:N ratio, SMBC, and mineral N under land uses change dominated the microbial community and functional structure.