Dryland Cropping Research Articles

Unequal contribution of two paralogous CENH3 variants in cowpea centromere function

In most diploids the centromere-specific histone H3 (CENH3), the assembly site of active centromeres, is encoded by a single copy gene. Persistance of two CENH3 paralogs in diploids species raises the possibility of subfunctionalization. Here we analysed both CENH3 genes of the diploid dryland crop cowpea. Phylogenetic analysis suggests that gene duplication of CENH3 occurred independently during the speciation of Vigna unguiculata. Both functional CENH3 variants are transcribed, and the corresponding proteins are intermingled in subdomains of different types of centromere sequences in a tissue-specific manner together with the kinetochore protein CENPC. CENH3.2 is removed from the generative cell of mature pollen, while CENH3.1 persists. CRISPR/Cas9-based inactivation of CENH3.1 resulted in delayed vegetative growth and sterility, indicating that this variant is needed for plant development and reproduction. By contrast, CENH3.2 knockout individuals did not show obvious defects during vegetative and reproductive development. Hence, CENH3.2 of cowpea is likely at an early stage of pseudogenization and less likely undergoing subfunctionalization.

The State of the Art in Modeling Waterlogging Impacts on Plants: What Do We Know and What Do We Need to Know

AbstractModels are key tools in our quest to better understand the impacts of soil waterlogging on plant growth and crop production. Here, we reviewed the state of the art of modeling approaches and compared the conceptual design of these models with recent experimental findings. We show that many models adopt an aeration stress (AS) principle where surplus water reduces air‐filled porosity, with implications for root growth. However, subsequent effects of AS within each model vary considerably. In some cases, AS inhibits biomass accumulation (e.g. AquaCrop), altering processes prior to biomass accumulation such as light interception (e.g. APSIM), or photosynthesis and carbohydrate accumulation (e.g. SWAGMAN Destiny). While many models account for stage‐dependent waterlogging effects, few models account for experimentally observed delays in phenology caused by waterlogging. A model intercomparison specifically designed for long‐term waterlogged conditions (APSIM‐Oryza) with models developed for dryland conditions with transient waterlogging would advance our understanding of the current fitness for purpose of exsiting frameworks for simulating transient waterlogging in dryland cropping systems. Of the point‐based dynamic models examined here, APSIM‐Soybean and APSIM‐Oryza simulations most closely matched with the observed data, while GLAM‐WOFOST achieved the highest performance of the spatial‐regional models examined. We conclude that future models should incorporate waterlogging effects on genetic tolerance parameters such as (1) phenology of stress onset, (2) aerenchyma, (3) root hydraulic conductance, (4) nutrient‐use efficiency, and (5) plant ion (e.g. Fe/Mn) tolerance. Incorporating these traits/effects into models, together with a more systematic model intercomparison using consistent initialization data, will significantly improve our understanding of the relative importance of such factors in a systems context, including feedbacks between biological factors, emergent properties, and sensitive variables responsible for yield losses under waterlogging.

Subsistence Agriculture Productivity and Climate Extreme Events

The occurrence of rainfall extreme events leads to several environmental, social, cultural, and economic consequences, heavily impacting agriculture. The analysis of climate extreme indices at the municipal level is of the uttermost importance to the overall study of climate variability and regional food security. Corn, bean, and cassava are among the most cultivated temporary subsistence crops. Thus, the objective of this study was to analyze the relationship between subsistence agriculture productivity and the behavior of rainfall extreme indices in the Rio Grande do Norte state in the period from 1980 to 2013. We used the dataset provided by Xavier (2016) and the climate extreme indices obtained through the Expert Team on Climate Change Detection and Indices. Crop productivity data were retrieved from the Municipal Agriculture Survey from the Brazilian Institute of Geography and Statistics system. The methodology evaluated the behavior and the relationship between agricultural productivity time series and extreme precipitation indicators. We applied the following statistical techniques: descriptive analysis, time series trend analysis by the Mann-Kendall test, cluster analysis, and analysis of variance to check for equal means between identified groups. Cluster analysis was considered an adequate tool for the comprehension of data spatial distribution, allowing the identification of five homogenous subregions with different precipitation patterns. Rainfall extreme indices allowed the analysis of regional conditions regarding consecutive dry days, annual precipitation in wet days, and heavy rainfall. Trends were identified in these indices and they were significantly correlated with dryland crops productivity, indicating a direct relationship between water availability and regional agroclimatic stress.

Contour Farming Improves Soil Moisture and Dry Land Crop Productivity on Rainfed Alfisols

A field experiment was conducted during kharif 2019 on Alfisols to find out the impact of intercropping and contour farming on total system productivity and soil moisture, under rainfed conditions. The results revealed that intercropping of mung bean with pigeon pea (MB+PP 4:1) was found to be highly productive and economical than corn+ pigeon pea (C+PP 4:1). Further, contour farming (CF) gave higher corn equivalent yield (CEY) and conserved more moisture than up down farming (UDF). The combination of MB+PP and CF has significantly out yielded (8019 kg ha-1) the MB+PP under UDF (6612 kg ha-1), C+PP under CF (4026 kg ha-1) and C+PP under UDF (3393 kg ha-1) in terms of CEY. Further, MB+PP and CF association recorded higher soil moisture, nutrient uptake, partial factor productivity (PPFN: 253.4 kg kg-1), agronomic efficiency of applied N (AEN: 46.79 kg kg-1) and rainfall use efficiency (RUE: 12.2 kg ha mm-1) besides higher net returns (Rs. 82608 ha-1) and B:C ratio (2.41).

Soil Management Systems to Overcome Multiple Constraints for Dryland Crops on Deep Sands in a Water Limited Environment on the South Coast of Western Australia

Deep sands on the south coast sandplain of Western Australia (WA) have multiple soil constraints including water repellence, high soil strength, low nutrient levels and subsoil acidity. The aim of the study was to test contrasting methods of managing water repellence and to assess their impacts on one or more soil constraints to crop production. These methods included seeding tyne design (knife point, winged points, paired row), soil wetting agent addition, strategic inversion tillage (rotary spading, mouldboard ploughing to 0.35 m) and clay-rich subsoil addition (170 t ha−1 with incorporation by spading to 0.20 or 0.35 m). Limesand (2 t ha−1) was applied as a split plot treatment prior to tillage. Cumulative crop yields were increased by 2.1–2.6 t ha−1 over five years by the strategic deep tillage and clay application treatments compared to the control. Water repellence was reduced by the inversion ploughing and subsoil clay addition treatments only. The effect of water repellence on crop establishment was expressed only in low rainfall years (Decile < 4) and mitigated by the paired row, wetting agent, spader and clay-amended treatments. In all years, plant numbers were adequate to achieve yield potential regardless of treatment. Soil K and plant tissue K and B were increased where clay had been applied. Inversion tillage reduced soil pH, organic carbon (OC) and macro nutrients in the 0–0.1 m layer although in most years there was no significant decline in plant tissue macro nutrient levels. Soil strength was reduced as a result of the inversion tillage to a depth of 0.35 m. However, the alleviation of soil strength and the crop yield responses diminished with time due to re-compaction. No crop response to the applied lime was found over five years at this site since the soil pHCaCl2 exceeded 4.7 within the root zone. In terms of soil constraints, we conclude that compaction was the dominant constraint at this site followed by water repellence and K deficiency.

Smash ridge tillage strongly influence soil functionality, physiology and rice yield.

The practice of smash-ridging on dry land crop cultivation has shown much promise. However, the mechanism how does soil functionality and root traits can affect rice yield under smash ridge tillage with reduced nitrogen fertilization have not yet been explored. To fill this knowledge gap, we used three tillage methods—smash-ridging 40 cm (S40), smash-ridging 20 cm (S20), and traditional turn-over plowing 20 cm (T)—and two rice varieties (hybrid rice and conventional rice) and measured soil quality, root traits, rice yield and their correlation analysis at different growth stages. Soil physical and chemical properties were significantly improved by smash-ridging, including improvements in root morphological and physiological traits during three growth stages compared with T. S40 had the highest leaf area index (LAI), plant height (PH), and biomass accumulation (BA). Increment in biomass and panicle number (PN) resulted in higher grain yield (GY) of 6.9–9.4% compared with T. Correlation analysis revealed that root total absorption area (RTAA), root active absorption area (RAA), and root area ratio (RAR) were strongly correlated with soil quality. Root injury flow (RIF) and root biomass accumulation (RBA) were strongly correlated with LAI and above-ground plant biomass accumulation (AGBA). Conclusively, S40 is a promising option for improving soil quality, root traits, and consequently GY.

Conversion of Land Use from Upland to Paddy Field Changes Soil Bacterial Community Structure in Mollisols of Northeast China.

Mollisols are extremely important soil resource for crop and forage production. In northeast China, it is a major land use management practice from dry land crops to irrigated rice. However, there is few data regarding soil quality and microbial composition in Mollisols during land use transition. Here, we analyzed the upper 30cm of soil from land with more than 30years of paddy use and from adjacent areas with upland crops. Our results showed that land use and soil depth had a significant effect on soil properties and enzyme activities. Soil moisture (SM) and soil organic carbon (SOC) contents were substantially higher in paddy fields than in upland crop lands, while nitrogen-related enzyme activities were lower. Following the land use change, bacterial diversity was increased and bacterial community composition changed. Taxonomic analyses showed that Proteobacteria, Chloroflexi, Firmicutes, and Bacteroidetes were the dominant phyla present. At family level, Gemmatimonadaceae decreased with land use change, while Syntrophorhabdaceae and Syntrophacea that play a part in methane cycling and nitrifying bacteria such as Nitrospiraceae increased, indicating that the structure and composition of the bacterial community might be a promising indicator of Mollisol health. Redundancy analysis indicated that land use type had a stronger effect on the soil bacterial community composition than soil depth. Additionally, bacterial community composition was closely associated with soil parameters such as soil moisture, pH, SOC, NO3--N, and NH4+-N. Overall, land use change affects the physical and chemical properties of the soil, resulting in changes in the composition of the soil bacterial community and flora. These changes could provide a view of the bacterial community assembly and functional shifts following land use change.

Temporal Dynamics of Rhizobacteria Found in Pequin Pepper, Soybean, and Orange Trees Growing in a Semi-arid Ecosystem

Harsh environmental conditions in drylands force plants and their associated microbial communities to adapt to abiotic stresses. In semi-arid environments, climatic conditions and poor agricultural management have a strong impact on plant yield and thus, enhancing soil fertility by means of beneficial microorganisms such as plant growth-promoting rhizobacteria (PGPR) has been proposed as part of sustainable agricultural management. As drylands will increase due to climate change, studying microbial community dynamics of crops under such conditions is crucial as it might favor rhizobacteria adapted to drought. While the microbiome of many native dryland crops has been characterized, the microbial community composition from non-native crops under semi-arid environmental conditions is understudied. Thus, the aim of this study was to characterize the bacterial community associated with the roots of three crops with different growth cycles, cultivated in the same semi-arid environment, to understand their microbial community composition during the season with the highest temperature in northeast Mexico. We performed high throughput sequencing of the V3-V4 region of the 16S rRNA gene from root samples of Pequin pepper, soybean and orange trees. Classified taxa were evaluated according to crop, sampling time and climatologic parameters. Our findings revealed that changes in temporal dynamics of microbial communities correlate with environmental temperature. Moreover, the microbial community of pepper was more diverse and differed from that of soybean and orange. Regarding PGPR, 47.6% of the genera were shared among crops with a high relative abundance of Bacillus, but we also detected crop-specific microbial associations where Serratia was specific to orange trees and Rhodobacter to pepper. When analyzing PGPR in correlation to climatologic parameters, Bacillus was found to thrive under lower precipitation rates, higher temperatures and higher evaporation rates in pepper and orange. In contrast, some PGPR commonly used in commercial biofertilizers such as Rhizobium and Azospirillum were affected by high temperatures. This study provides a better understanding of the rhizobacterial assemblies of economically relevant crops grown under a semi-arid environment.

Detecting phenological changes in plant functional types over West African savannah dominated landscape

ABSTRACT Phenology is an important component in the climate system, and play a key role in controlling many feedbacks of vegetation to the climate systems. Differences in phenology of plant functional types (PFTs) due to the variation in seasonal cycles (e.g. changes in weather variability), the impact from land-use activities (e.g. fire) and their mechanisms for adaptation (e.g. climate change, regrowth/post-fire regeneration) have major implications in conservation planning and monitoring actions. Detecting phenological variations in PFTs is therefore of great importance to quantitative remote sensing applications, especially in a biome as diverse and complex as savannah. In this study, we implement Savitzky–Golay filtering and the Breaks For Additive Seasonal and Trend (BFAST) algorithms to detect changes in PFTs based on their phenological events using Moderate Resolution Imaging Spectroradiometer (MODIS), normalized difference vegetation index (NDVI) data from 2001 to 2018. In this region, PFTs present distinct seasonal, annual and interannual variability. Woody phenology presents early green-up dates with a prolonged senescence period and invariably observed the longest growing season length (GSL). The relationship between the start of season (SOS) or end of season (EOS) was assessed for each PFT to find out the extent to which they determine GSL for different PFTs. GSL is mostly determined by the SOS in woody savannah (coefficient of determination (R²) =0.41, p <0.01), open shrubs and (R² =0.79, p <0.001), grassland (R² =0.35, p <0.01) while EOS determined the GSL for both dryland crops (R² =0.75, p <0.001) and paddy rice (R² =0.69, p <0.001). We compared the interannual variability of woody savannah and other PFTs by measuring the differences of their phenological indicators using Welch’s t-test. All PFTs show statistically significant difference with the GSL of woody savannah except open shrubs (p = 0.23). The abrupt vegetation changes estimated with BFAST varied by PFT. Some PFTs are more resilient to harsh environmental conditions than others. While woody species present a few abrupt changes, grass phenology is more vulnerable to disturbance, seasonally as well as in the trend components (large number of abrupt changes) with browning trend following an abrupt negative change. In all PFTs, breakpoint (disturbance) assessed using BFAST negatively correlate with precipitation data which means the magnitude of disturbance decreases with increasing precipitation. Woody species had an r (correlation coefficient) value of -0.5 while grassland had r = -0.7 which is a further indication that grass phenology responds more strongly to annual precipitation than the woody species. These results show that MODIS NDVI time-series data can be used to distinguish the phenological events of different PFTs in West African savannah dominated landscape.

The effects of dryland cropping system intensity on soil function and associated changes in macrofauna communities

AbstractCrop production in water‐limited environments may be enhanced through improved soil function by facilitating precipitation capture and erosion control. Soil macrofauna are known to support improved soil structure and water dynamics through ecosystem engineering activities, and their populations can be influenced by management. We examined the effect of bare summer fallow frequency on soil macrofauna communities and soil physical properties in a long‐term (32‐yr) dryland no‐till agroecosystem experiment at two sites in eastern Colorado, USA. Treatments represented a gradient of fallow frequency and organic matter inputs, which included wheat (Triticum aestivum L.)–fallow, wheat–corn (Zea mays L.)–fallow, and continuously cropped with no planned summer fallow. The design also included a perennial grass treatment with minimal management consisting of six native grasses. We observed links between soil macrofauna and soil functional metrics, particularly related to soil aggregation and water infiltration. There was a trend toward higher macrofauna populations and soil function with increased cropping system intensity, and perennial grass outperformed the cropped treatments significantly for most soil health parameters. Multivariate analyses revealed that different treatments support relatively distinct macrofauna communities. Our results suggest that soil macrofauna populations may be important facilitators of soil structure and associated water dynamics in dryland no‐till agroecosystems and respond positively to reduced fallow and higher organic inputs.

Trends in Runoff From Dryland, Cropped Fields on the Texas High Plains, and Implications for Their Management

Capturing precipitation as soil moisture is essential for successful dryland crop production, especially in semi-arid regions. Runoff is a loss of precipitation that does not result in increased soil moisture. Therefore, understanding the factors affecting runoff from cropped fields is important to successful dryland farming. Runoff frequency and volume were assessed using data from 1990-2009 from a long-term wheat-sorghum-fallow rotation near Bushland, Texas (USA), an area with an annual precipitation of approximately 500 mm and pan evaporation rate of over 2,000 mm. The likelihood that a rainfall event generated runoff increased with increasing rainfall volume such that all storms in excess of 50 mm yielded runoff. Runoff volume also increased with storm intensity. Rainfall in the preceding week was positively related to runoff volume. Runoff tended to be greater in no-till plots as compared to stubble mulched plots. During El Nino and La Nina phases of the El Nino-Southern Oscillation the number of precipitations during the months of December through February and November through January, respectively, tended to be higher and lower, respectively. There also was a tendency for rainfall events during the El Nino phase to be of greater volume. However, the data did not support the hypothesis that greater winter rainfall with the El Nino event was associated with greater runoff. Therefore, greater rainfall during the El Nino phases should have been available for crop production. These results are discussed with regarding crop management practices for the Texas High Plains.

Soil organic matter dynamics in semiarid agroecosystems transitioning to dryland.

Recent interest in improving soil health and agricultural sustainability recognizes the value of soil organic carbon (SOC) sequestration and nutrient cycling. The main goal of this study was to evaluate the response of various SOC and nitrogen (N) components in semiarid cropping systems transitioning from limited-irrigation to dryland and a restored grassland in the Southern High Plains of USA. Cropping systems evaluated include dryland winter wheat (Triticum aestivum L.)–sorghum (Sorghum bicolor L.)–fallow with conventional tillage (DLCTF) and no-tillage (DLNTF), limited-irrigation winter wheat–sorghum–fallow with no-tillage and cover cropping (LINTC) and no-tillage fallow (LINTF), and an undisturbed grassland (NG). Soil samples were collected from 0–15 cm and 15–30 cm depths and analyzed for SOC, total N, inorganic N, and soil microbial biomass carbon (SMBC) contents. The CO2 and N2O release during a eight-weeks long laboratory incubation were also analyzed. Results show 14% and 13% reduction in SOC and total N from 0–30 cm depth with the transition from limited-irrigation to dryland cropping systems while 51% more SOC and 41% more total N with the transition to grassland. The SMBC was 42% less in dryland cropping systems and 100% more in NG than the limited-irrigation cropping systems. However, the grassland was N limited, with 93% less inorganic N in NG compared to only 11% less in dryland cropping systems than in limited-irrigation cropping systems. The microbial respiration measured as CO2-C was highest in NG, followed by limited-irrigation and dryland cropping systems. The N2O-N release showed the lowest rate of N loss from dryland cropping systems, followed by NG and limited-irrigation cropping systems. This study demonstrated loss of SOC and N in agroecosystems transitioned to dryland crop-fallow systems, with greater magnitude of change observed in the biologically active fraction of soil organic matter. Grassland restoration could be an important strategy to increase SOC and nutrients in hot, dry, semiarid agroecosystems transitioning to dryland.

A Dynamical Simplified Swarm Optimization Algorithm for the Multiobjective Annual Crop Planning Problem Conserving Groundwater for Sustainability

In large-scale agriculture, insufficient irrigation water may lead to overpumping of groundwater, increasing the risk of land subsidence. Growing dryland crops can effectively decrease the demand for irrigation water. However, the previous works on annual crop planning (ACP) focused on maximizing the profit through growing wetland crops and consuming much water. For sustainability, in this article, we propose a mathematical programming model for an ACP that allocates a land area for growing dryland and wetland crops to maximize the total profit and minimize the total irrigation water used for multiple cropping, under practical constraints. The simplified swarm optimization (SSO) improves the particle swarm optimization with four probabilities to determine the operations of updating solutions. We further propose dynamic SSO (DSSO) to solve the concerned ACP in which the four probabilities are adjusted dynamically according to the performance of the operations executed. Through simulation on a case study, the proposed DSSO demonstrates high performance over some classical approaches.

Evaluating the effects of plastic film mulching patterns on cultivation of winter wheat in a dryland cropping system on the Loess Plateau, China

Plastic film mulching (PFM) can increase or stabilize crop yields worldwide when applied to agricultural planting systems, especially in arid and semi-arid areas. Although the adverse effects that are caused by residual plastic film, such as plastic pollution, are becoming a global concern, the application of PFM will not be replaced by other materials in the short-term in agriculture. It is important to understand the various PFM patterns (different mulching periods and coverage rates) that impact on soil physicochemical properties and characteristics of crop growth. Therefore, based on a field experiment that we established in 2002, we conducted consecutive field observations from 2013 to 2016 to determine the optimum PFM mulching period and coverage rate. Three mulching periods were included: (I) summer fallow period (FM), (II) growth period (GM), and (III) whole growth year (WM). Two coverage rates were included: (i) 50%, half mulching (HM), and (ii) 100%, total mulching (TM). That is, there were six different PFM treatments. No mulching (NM) over the growth years was considered the CK treatment. PFM increased canopy height and leaf area index of winter wheat (Triticum aestivum L.) in the growing season by 29.5% and 19.4%, respectively. Average winter wheat grain yields of various PFM patterns were 5318.5 kg ha−1 and 4557.7 kg ha−1 in 2013–2014 and 2015–2016, respectively; these yields were 13.8% and 23.7% higher than NM in 2013–2014 and 2015–2016, respectively. However, the difference in the growth characteristics and grain yield of winter wheat under various PFM patterns resulted from the change in the mulching period and coverage rate. Winter wheat grain yield and biomass increased with GM and WM compared with FM and NM in normal rainfall years. PFM coverage rates improved yield significantly (P < 0.05) and influenced soil nutrient concentrations. HM maintained or increased soil organic matter (SOM) and total nitrogen concentrations, but TM decreased SOM concentration by 8.3%. Water use efficiency (WUE) and rainfall use efficiency (RUE) were improved by various PFM patterns. Furthermore, WM had the most significant impact on SOM concentrations, GM was second, and FM was minor. Considering the costs and benefits of PFM patterns, the half coverage rate of PFM during the whole year (FWH) had the best index (BI) value, and the total coverage rate of PFM during the growth period (FGT) and the half coverage rate of PFM during the growth period (FGH) had higher BI values than other PFM patterns; the values for BI for FWH, FGT, and FGH were 10.3, 8.9, and 8.5, respectively. In conclusion, ignoring the amount of PFM pollution in the environment (or use biodegradable film instead of polyethylene film), FWH was the best PFM pattern with the highest WUE and RUE in dryland rainfed agriculture. But, to decrease the amount of PFM application and pollution, FGH was more beneficial for soil health with a low coverage rate and short mulching period. FGH was the optimal pattern for PFM when applied to winter wheat on the Loess Plateau, China based on our field experiment.

Historically Rice-Farming Societies Have Tighter Social Norms in China and Worldwide

Data recently published in PNAS mapped out regional differences in the tightness of social norms across China. Norms were tighter in developed, urbanized areas and weaker in rural areas. We tested whether historical paddy rice farming has left a legacy on social norms in modern China. Pre-modern rice farming could plausibly create strong social norms because paddy rice relied on irrigation networks. Rice farmers coordinated their water use and kept track of each person’s labor contributions. Rice villages also established strong norms of reciprocity to cope with labor demands that were twice as high as dry-land crops like wheat. In line with this theory, China's historically rice-farming areas had tighter social norms than wheat-farming areas, even beyond differences in development and urbanization. Rice-wheat differences were just as large among people in 10 neighboring provinces (N = 3,835) along the rice-wheat border. These neighboring provinces differ sharply in rice and wheat, but little in latitude, temperature, and other potential confounding variables. Outside of China, rice farming predicted norm tightness in 32 countries around the world. Finally, people in rice-farming areas scored lower on innovative thinking, which tends to be lower in societies with tight norms. This natural test case within China might explain why East Asia — historically reliant on rice farming — has tighter social norms than the wheat-farming West.

Using Multisource Geospatial Data to Identify Potential Wetland Rehabilitation Areas: A Pilot Study in China’s Sanjiang Plain

Wetland rehabilitation, highlighted in the United Nations (UN) Sustainable Development Goals (SDGs), is imperative for responding to decreased regional biodiversity and degraded ecosystem functions and services. Knowing where the most suitable wetland rehabilitation areas are can strengthen scientific planning and decision-making for natural wetland conservation and management implementation. Therefore, we integrated multisource geospatial data characterizing hydrological, topographical, management, and policy factors, including maximum surface water coverage, farming time, anthropogenic disturbance, and wetland protection level, to identify potential wetland rehabilitation areas in the Sanjiang Plain (SJP), the largest marsh distribution and a hotspot wetland loss region in China. Our results indicate that a total of 11,643 km2 of wetlands were converted into croplands for agricultural production from 1990 to 2018. We estimated that 5415 km2 of the croplands were suitable for wetland rehabilitation in the SJP, of which 4193 km2 (77%) have high rehabilitation priority. Specifically, 63% of the potential areas available for wetland rehabilitation are dry croplands (3419 km2), the rest (37%) being paddy fields. We argue that the selected indicators and approach used in this study to determine potential wetland rehabilitation areas could guide their investigation, at either the provincial or national scale and would be beneficial to conservation and sustainable management of wetlands in the SJP.

Yield reduction under climate warming varies among wheat cultivars in South Africa

Understanding extreme weather impacts on staple crops such as wheat is vital for creating adaptation strategies and increasing food security, especially in dryland cropping systems across Southern Africa. This study analyses heat impacts on wheat using daily weather information and a dryland wheat dataset for 71 cultivars across 17 locations in South Africa from 1998 to 2014. We estimate temperature impacts on yields in extensive regression models, finding that extreme heat drives wheat yield losses, with an additional 24 h of exposure to temperatures above 30 °C associated with a 12.5% yield reduction. Results from a uniform warming scenario of +1 °C show an average wheat yield reduction of 8.5%, which increases to 18.4% and 28.5% under +2 and +3 °C scenarios. We also find evidence of differences in heat effects across cultivars, which suggests warming impacts may be reduced through the sharing of gene pools amongst wheat breeding programs.

New winter crops and rotations for the Pacific Northwest low‐precipitation drylands

AbstractThis article is an overview of recent advances in dryland cropping in the region of the Inland Pacific Northwest of the United States (PNW) that receives &lt;300 mm annual precipitation. The climate of the region is Mediterranean‐like with wet winters and dry summers. For the past 130 yr, monocrop 2‐yr winter wheat (Triticum aestivum L.)–fallow (WW–F) has been the dominant rotation practiced on &gt;90% of rainfed cropland throughout this region. Rapid advances in technology in the past several decades and the realities of dryland farm economics prompted most farmers to expand their land area and adopt conservation tillage and no‐tillage practices. Three relatively new crops have gained some foothold in the past decade. These crops are winter pea (WP) (Pisum sativum L.), winter canola (WC) (Brassica napus L.), and winter triticale (WT) (X Triticosecale Wittmack). Like WW, all three of these “new” winter crops need to be planted in late August–early September into carryover soil moisture after a 13‐ to 14‐mo fallow period to achieve optimum yield potential. Researchers and farmers have experimented with a multitude of spring‐planted crops but, to date, all have shown high year‐to‐year variability in yield and none have been economically viable in the long term. The focus of this paper is to summarize major research conducted on WP, WC, and WT, as well as farmers’ attitudes on the potential of these three winter crops for wheat‐based rotations in the PNW drylands.

Soil fertility constraints and management to increase crop yields in the dryland farming systems of Aceh, Indonesia

In Aceh, Indonesia, low dryland crop yields entrench rural poverty. The lack of soil fertility information hinders the development of soil management programs to assist farmers to increase crop yield. This study identified soil-based constraints to production and management options to increase crop yield. We analysed 254 soil samples from 127 dryland cropping sites across Pidie, Bireuen, Aceh Besar and Aceh Barat districts for pH, soil organic carbon (SOC), total nitrogen (N), phosphorus (P), base saturation (BS) and cation exchange capacity (CEC). The dominant soils were Entisols, Inceptisols and Ultisols, with some Andisols and Mollisols. Overall, the CEC range was 10–60 cmol(+) kg–1 and available P was 0.5–702 mg kg–1 but most had poor fertility: SOC &amp;lt; 20.0 g kg–1, total N &amp;lt; 2.0 g kg–1, low basic cations and BS &amp;lt; 40%. The Ultisols and some Entisols and Inceptisols were acidic, with aluminium saturation &amp;gt;20% and available P &amp;lt; 6.5 mg kg–1. To sustainably increase crop yield, we concluded that these soils need lime where acidic, fertilisers for nutrients and stable carbon-rich amendments for system stability. This dataset will guide future agricultural research and development programs in Aceh to improve farmer practices and food security.

Dryland cropping system impact on forage accumulation, nutritive value, and rainfall use efficiency

AbstractForage cropping systems have greater precipitation use efficiency compared with cereal grains and oilseed cropping systems. However, information is limited to which forage species and forage rotation system increases productivity the most in the central Great Plains. The objective of this research was to identify the productivity and nutritive value of forage sorghum [FS, Sorghum bicolor (L.) Moench], winter triticale [WT, ×Triticosecale Wittm. ex A. Camus (Secale × Triticum)], and spring triticale (ST) crop rotations in the central Great Plains. The study was conducted from 2008 through 2011 at Garden City, Jetmore, and Tribune, KS. The experimental design was a randomized completed block with four crop rotation treatments: continuous FS–FS, continuous WT–WT, annual double‐crop WT/FS, and 2‐yr, double‐crop WT/FS–ST rotations. The annualized forage accumulation from WT/FS–ST rotation at Garden City, Jetmore, and Tribune were 30, 53, and 62% greater than annualized yields from the WT–WT rotation, respectively. The annualized forage accumulation from double crop WT/FS rotation were 55 and 148% greater than annualized forage accumulation from WT–WT rotation at Garden City and Jetmore. Overall productivity of a rotation was in the order WT/FS &gt; WT/FS–ST or FS–FS &gt; WT–WT. Despite its greater productivity, it was difficult to implement field operations (planting and harvesting) in the WT/FS rotation due to insufficient time in the growing season and because, often, there was little to no soil water available at planting. We concluded the WT/FS–ST rotation was less intense and more easily adoptable than the WT/FS rotation and has sufficient diversity to utilize resources better than continuous FS–FS or WT–WT rotations.