Fallow Management Research Articles

Long‐term effects of management practices on soil water, yield and water use of dryland wheat: A global meta‐analysis

AbstractSoil water conservation in dryland agriculture mainly depends on precipitation. We chose 35 long‐term experiments and analysed the data by using meta‐analysis to check how fallow management methods affect soil water storage of dryland winter wheat planting (SWS), precipitation storage efficiency (PSE), crop yield and water use efficiency (WUE). No‐tillage (NT), compared to conventional tillage (CT) in the fallow period, increased PSE, SWS, grain yield and WUE by 32.9%, 27.1%, 30.5% and 22.6%, respectively. Reduced tillage (RT) and subsoil tillage (ST) increased PSE by 15.2% and 11.7%, SWS by 17.4% and 15.0% and grain yield by 15.5 and 13.8%, respectively, but these had a non‐significant effect on WUE. The conservation tillage methods interacted significantly with the residue management and fallow mulching practices. Compared to CT, the conservation tillage methods with fallow mulching increased PSE, SWS, grain yield and WUE, but the growing of cover crops (designated as biological mulching) decreased PSE, SWS and grain yield by 17.3%, 13.0% and 32.0%, and had a non‐significant impact on WUE. Under the condition of straw mulching, NT increased PSE, SWS, grain yield and WUE by 43.7%, 38.1%, 40.6% and 42.9%, respectively, compared to CT. NT and RT increased the PSE, SWS and WUE, under normal mean annual precipitation (MAP), however, ST increased these observations under wet MAP, compared to CT. The effects of tillage methods varied with soil texture, and they were highly interrelated with water conservation, wheat yield and water use. We conclude that compared to conventional tillage, the conservation tillage methods increased soil water conservation during the fallow period, which increased wheat yield and water use. Moreover, NT with or without residue retention increased the fallow water conservation and wheat yield. Crop residues should be retained while applying RT and ST to grow winter wheat in dryland regions.

Influence of agroforestry systems on earthworm diversity and soil properties in a Sudano-Sahelian landscape

Agroforestry systems promote a range of ecological base management to support sustainable agriculture. However, the influence of agroforestry management on soil biodiversity is still poorly investigated in Sudano-Sahelian landscapes. This study aims to guide sustainable management for soil biodiversity conservation in agroforestry systems by determining the drivers of earthworm diversity with their abundance and corresponding soil properties. Nested sampling following three management systems (agroforestry fallow, agroforestry intercropping, agroforestry grazing) and the protected area as a baseline, were designed for data collection in a Sudano-Sahelian landscape. Earthworm inventory and soil sampling (0–10 cm), coupled with a survey focusing on the cropping and fallowing duration with other agricultural practices (herbicide use, soil tillage), were conducted on the farm. The soil analysis included soil texture, bulk density and a suite of chemical analyses (pHKCl, C and N, available macro and micronutrients). The data were analyzed using generalized linear models (GLMs) and ANCOVA to determine the effects of agroforestry systems on earthworm abundance and soil properties. A Principal Component Analysis (PCA) was performed to determine the relationship between the species richness of earthworms, agroforestry systems and soil properties. The results showed a diversity of five species belonging to the endogeic and epigeic ecological groups numbered at 7 ± 3 to 22 ± 10 individuals m−2 (mean ± standard deviation). In agroforestry fallow systems, earthworm diversity and abundance were both highest, and the abundance increased with the fallow duration. The prolongation of cropping duration coupled with herbicide use in agroforestry intercropping systems decreased significantly the abundance of earthworms. Agroforestry grazing systems increased significantly soil C, N and available nutrients, but the abundance of earthworms and species richness were the lowest likely due to soil destructuration by trampling. Overall, soil texture controlled the species richness of earthworms. Fallow management and agricultural practices with fewer herbicide use and soil destructuration, are essential to improve earthworm abundance and diversity.

Impact of bare fallow management on soil carbon storage and aggregates across a rock fragment gradient

AbstractBackgroundOur understanding of C storage in soils lacks insights investigating organic matter (OM) depletion, often studied in bare fallow systems. The content of coarse rock fragments is often excluded, whereas it may affect C storage.AimsWe aim to contribute to a better understanding of the impact of bare fallow on C storage mechanisms in the soil as influenced by its coarse rock fragment contents. We investigated whether bare fallow induced a depletion of C in OM fractions and analyzed to which extent this affected soil aggregate size distribution and the C loading of the clay‐sized fraction.MethodsA comparison of 14 years bare fallow management with adjacent cropped soils located in Selhausen (Germany) provided a gradient of coarse rock fragments of 34%–71%, from which sites with three different fine earth (FE) contents were compared. Across the FE gradient, we isolated particulate OM and mineral‐associated OM fractions, obtained microaggregate and macroaggregate size fractions, and quantified the C loading.ResultsBare fallow management induced an OM depletion at lower contents of FE. There, the management influence was more concentrated onto less FE volume. The contribution of both particulate and mineral‐associated OM fractions to the C in the low‐FE soils decreased. The C loading increased under bare fallow, compared to cropped soil. In the low‐FE soil, we also found less macroaggregates, whereas the C content decreased in some microaggregate size fractions.ConclusionsA high content of coarse rock fragments can enhance OM depletion decreasing mineral‐associated and particulate C under bare fallow.

The Role of Fallows in Sustainable Development

Abandonment of crop production on agricultural lands for several or more years is a widespread practice not only in Europe but also around the world. Economic and political considerations lead to the abandonment of crop production on the poorest lands, although sometimes agriculturally valuable lands are also excluded from farming. Fallow land can be afforested, designated as a dedicated protection area, exposed to natural succession, or used to grow biomass for energy purposes. However, the most important role of agricultural land should be to ensure food safety. The set-aside land with high production potential should be treated in a special way. While lying fallow, the soil can have its fertility sustained or even improved considerably. To this aim, uncultivated land should be properly protected by growing a permanent cover of plant species which will have a positive influence on the soil’s physical, chemical, and biological characteristics. Depending on the geographical location, different plant species will have a beneficial effect on set-aside soil. Given economic and environmental considerations, the best solution is to sow a mixture of grasses and legumes, which can improve substantially the biodiversity on fallow fields, raise the soil’s fertility, ensure high CO2 sequestration ratios, and influence beneficially the soil’s nutritional status and nutrient management. Soil protection can be provided for many years with little effort. The most recent reports implicate that it is possible to achieve several economic and environmental aims simultaneously in the course of the management of land excluded from agricultural production. These aims include the improvement of biodiversity, control of greenhouse gas emissions, generation of energy, and readiness to resume production of commodity plants. Proper management of fallows corresponds well with the challenges defined in the Green Deal for Europe or the US Green New Deal.

Disentangling the effects of management, field characteristics of fallows, and surrounding landscape to promote steppe bird conservation

The steep decrease of fallow area in the last years has been directly related to steppe bird population declines in Europe, as fallow lands are a crucial habitat for shelter, food, and nesting resources. However, the potential of fallows to foster steppe bird populations may vary greatly depending on factors at both the landscape and field scale, which may also interact differently depending on the species. This study uses data from more than 3000 ha of fallow land in north-eastern Spain specifically managed for steppe bird conservation to explore which are the characteristics that maximize their conservation value for steppe bird species. We used variance partitioning methods to separate the effects of fallow management (e.g., vegetation height or fallow age) from field characteristics (e.g., field size) and landscape context (e.g., amount of surrounding shrubland area) on the occurrence and abundance of target steppe bird species. Even if fallow management was optimized to meet the requirements of steppe birds, field characteristics and landscape context had important effects (i.e., explained high part of the variance) in maximizing occurrence and abundance. All studied species consistently preferred bigger and dominant fallows (i.e., those at a higher relative elevation). Conservation measures promoting fallows for the conservation of steppe birds should consider mechanisms to optimize the selection of fields. Integrating optimal field selection might be too specific and challenging for agri-environment-climate measures (AECM), however it could be a cost-effective measure when implemented in local or targeted conservation plans, such as those applied within priority areas, protected areas, or compensatory measures.

How to Improve the Benefits of Short-Term Fallow on Soil Physicochemical and Microbial Properties: A Case Study from the Yellow River Delta

Fallowing is regarded as an effective method for the self-recovery management of farmland and is generally used in cultivated land management. Studies have shown that long-term fallow has many ecological and environmental benefits. However, the long-term fallowing of farmland has also caused a decline in the grain production of farmland for a period of time. Short-term fallow can reduce the risk of food insecurity, but there are few studies on short-term fallow, especially on the comparation of different fallowing management methods and their relationship with soil microbial ecology. Our study has focused on seven treatments. Firstly, the traditional farming method was set as the control group. Native vegetation and crop-pasture vegetation were set as the fallowing vegetation. There were three irrigation–fertilization levels for each vegetation. The effects of the sampling times showed that the impact of fallow management on the soil properties became gradually stronger with time. The interactions between the sampling times and treatments showed a significant impact on organic carbon and total nitrogen. There was a significant impact of fallow management on the inorganic carbon accumulation and ammonia nitrogen consumption. Microbial biomass carbon was significantly increased by fallowing. Fallowing with irrigation could enhance the soil microbial nitrogen transformation. Some genera associated with assisting diseases were significantly increased by the native vegetation fallow and grass fallow with farmyard manure. The fallow with native vegetation showed more advantageous ecological benefits than the crop-pasture vegetation fallow. Although the crop-pasture vegetation followed the principle of ecological intensification, it failed to show better ecological benefits in the short fallow period. In irrigation management, the benefits of native vegetation and crop-pasture vegetation are similar. However, considering the lower cost of crop-pasture vegetation, crop-pasture vegetation fallow with irrigation could be a better choice. If it is difficult to implement conservation measures during the fallowing process, native vegetation fallowing without management may be the only fallowing choice.

Construction of an integrated framework for assessing ecological security and its application in Southwest China

Ecological security is a prerequisite for the sustainable development of a region. The question of how to carry out a scientific and accurate ecological security assessment is therefore of great significance. Southwest China faces the dual challenges of maintaining ecological security and advancement of the economy. Thus, an evaluation of its ecological security status is essential. In this study, ecosystem services, ecological sensitivity, and landscape patterns were used to construct an integrated framework for assessing ecological security. The ecological security status of 549 counties (cities and districts) in Southwest China were evaluated for the years 2000, 2020, 2015, and 2018. Levels of ecological security in northern Guangxi, the western part of the Chengdu Plain, and the western and southern parts of Yunnan Province were generally higher than those in other areas. Conversely, levels of ecological security in western Sichuan Province, in metropolitan areas of Yunnan Province, and in the cities of Chengdu, and Chongqing were consistently low. From 2000 to 2018, the ecological security index (ESI) values of 52.82% of the study units concentrated in central and western Sichuan, eastern and southern Yunnan, and central and southern Guangxi increased, whereas those of 47.18% of study units concentrated in northeastern Sichuan, Chongqing, Guizhou, and northern Guangxi decreased. The level of ecological security in Southwest China is affected by the climate and by human activities. The following recommendations emerged from the study’s findings for maintaining the region’s ecological security. Local governments should strengthen the construction of cleaner industries, continue to return farmland to forests and promote crop rotation and fallow management, increase investments in and the development of nature reserves, implement outmigration schemes for ecologically fragile regions, and improve land conservation and intensive land use.

Winter cover crop impact on soil health in Texas Rolling Plains dryland cotton

AbstractThe Rolling Plains of Texas are historically semi‐arid with sporadic, high intensity storms followed by periods of long drought. Fallow management is a common practice intended to store soil water, but leaves the bare soil exposed to erosive forces that can diminish the soil productivity. Cover crops in no‐till (NT) agriculture have been proposed to increase soil health under environments with low precipitation as an alternative to fallow management. This study evaluated multiple treatments in a dryland cotton system including: (1) conventional tillage (CT); (2) NT; and NT with the following cover crops: (3) wheat; (4) Austrian winter pea; (5) crimson clover; (6) hairy vetch; and (7) mixed species cover. Soil samples were collected at 0, 3, and 6 weeks after cover crop termination and analyzed for soil organic carbon, total nitrogen, inorganic N, water‐extractable organic carbon, water‐extractable organic nitrogen, carbon mineralization, and phospholipid fatty acid analysis. For all parameters tested, there was no significant difference between CT and NT at any date or depth, so the addition of cover crops to NT cotton systems might be needed in order to enhance NT in regard to soil function. The multi‐species mixed treatment was predicted to perform the best out of the cover crop treatments due to its combined benefits from grasses and legumes. However, the single‐species Austrian winter pea treatment had 24% and 28% higher soil carbon and nitrogen than no‐till without a cover crop, and can be a useful alternative to fallow management under these dryland agriculture conditions.

The effect of short-term fallowing on the microbial communities in forest soil cultivated with ginseng: Preliminary research.

Continuous cultivation of ginseng crops in fixed plots can lead to disease outbreaks, yield losses and replanting failures. Fallow periods can help restore soil health and increase the sustainability of agricultural systems; however, taking land out of production for extended periods is often not feasible. Short-term fallow periods could restore soil health, but few studies have examined the effects of short-term fallow treatment on the health of soil in ginseng fields. In this preliminary study, we used metagenomic analysis to assess changes in the abundance of major ginseng pathogens and soil health overall following a short-term fallow period in a region in the Changbai Mountains. A sample from a forest plot (Hx0ks), was compared to a sample from a field where ginseng was previously cultivated and then had been left fallow for two years (Hx2), and a sample from a field that had been fallow for two years and was subsequently replanted with ginseng (Clsd). Soil that was fallow for two years, and then replanted with ginseng, showed reduced nutrient content and lower diversity of soil bacterial and fungal communities than soil that remained fallow. Candidatus Solibacter (5%) and Rhizomicrobium (3%) were the most abudant bacterial genera in Hx2. Rhizomicrobium (4%) and Gemmatimonas (3%) were the most abundant bacterial genera in Clsd. Mortierella (22%) and Peziza (12%) dominated the fungal community in Hx2. Lecanicillium (38%) and Mortierella (13%) dominated the fungal community in Clsd. Fallow periods also increased the functional diversity of soil as predicted by PICRUSt and decreased the relative abundance of the pathogenic fungi. Preliminary findings were consistent with the hypothesis that fallow management in ginseng cultivation can improve soil microbial community structure and function and reduces the number of plant pathogens; however, testing this hypothesis will require replicated plots.

Diversifying and perennializing plants in agroecosystems alters retention of new C and N from crop residues.

Managing soils to retain new plant inputs is key to moving toward a sustainable and regenerative agriculture. Management practices, like diversifying and perennializing agroecosystems, may affect the decomposer organisms that regulate how new residue is converted to persistent soil organic matter. Here we tested whether 12 years of diversifying/perennializing plants in agroecosystems through extended rotations or grassland restoration would decrease losses of new plant residue inputs and, thus, increase retention of carbon (C) and nitrogen (N) in soil. We tracked dual-labeled (13 C and 15 N), isotopically enriched wheat (Triticum aestivum) residue in situ for 2 years as it decomposed in three agroecosystems: maize-soybean (CS) rotation, maize-soybean-wheat plus red clover and cereal rye cover crops (CSW2), and spring fallow management with regeneration of natural grassland species (seven to 10 species; SF). We measured losses of wheat residue (Cwheat and Nwheat ) in leached soil solution and greenhouse gas fluxes, as well as how much was recovered in microbial biomass and bulk soil at 5-cm increments down to 20 cm. CSW2 and SF both had unique, significant effects on residue decomposition and retention dynamics that were clear only when using nuanced metrics that able to tease apart subtle differences. For example, SF retained a greater portion of Cwheat in 0-5 cm surface soils (155%, p = 0.035) and narrowed the Cwheat to Nwheat ratio (p < 0.030) compared to CS. CSW2 increased an index of carbon-retention efficiency, Cwheat retained in the mesocosm divided by total measured, from 0.18 to 0.27 (49%, p = 0.001), compared to CS. Overall, we found that diversifying and extending the duration of living plants in agroecosystems can lead to greater retention of new residue inputs in subtle ways that require further investigation to fully understand.

Rice-fallow Management in Eastern India: Challenges and Opportunities for Enhancing System Productivity and Profitability

Vast fallows in the rabi/dry season are an issue of serious concern in the agricultural production system of Odisha and other parts of eastern India. With a rainfed rice-based mono-cropping system, resource-poor and small &amp; marginal farmers of eastern India are forced to dwell in the vicious circle of poverty. Recently, the issue of rice-fallow is among the top agendas for the policymakers, and so public investment is happening. However, ad hoc investments in fallow intensification do not yield sustainable and satisfactory results as it is a very complex and multi-dimensional problem (biotic, abiotic, policy, and socio-economic) requiring attention at various levels of intervention. With this backdrop, based on secondary data and information and the review of literature, this paper discusses the key issues and challenges in rice-fallow development and recommends some strategic interventions needed for converting those fallow lands into croplands, particularly in rabi season. Also, the paper studies ongoing programs/schemes of central and state governments related to fallow management, keeping in view that research on fallow management must go in parallel with ongoing programs/schemes. Authors recommend that partners in a collaborative approach; should assess pathways of sequencing investment and intervention to catalyze the intensification of rabi fallows. If conceivable and low-to-medium risk pathways are identified, and associated convening and catalytic roles are defined for partners; policy dialogue and execution plan will not be an issue as all the local governments and agencies already understand the need for fallow management. This paper will be helpful for planners, policymakers, and development stakeholders while framing the policies, designing programs, setting implementation strategies, monitoring systems, critically analyzing potentially who can invest and where, etc., for a sustainable and environment-friendly agricultural system for poverty reduction, and food &amp; nutritional security.

Sown alfalfa pasture decreases grazing intensity while increasing soil carbon: Experimental observations and DNDC model predictions.

Grasslands are the most important land use in China and have experienced extensive degradation in the past few decades due to overgrazing. However, regionally viable solutions to grazing intensity alleviation remained elusive to date. Here, we evaluated the grazing intensity effects of sown alfalfa pastures in northern China using an experiment-modeling combined approach that involved six sites in field experiments and five provinces in DNDC modeling of sown alfalfa pasture's forage production and carbon sequestration potentials in marginal lands. Our results showed that the sown alfalfa pasture's dry-matter yield varied between 4.5 and 9.0 Mg ha-1 under rainfed and irrigated conditions, respectively, from 2025 to 2035. If half of the available marginal lands were mobilized for alfalfa forage production, these yield levels meant that livestock grazing intensity on natural grasslands may drop 8-13% under rainfed and 20-33% under irrigated conditions. Our results also showed that marginal land's soil organic carbon contents were systematically higher under sown alfalfa pasture than under fallow management by a big margin of 8.5 and 9.9 g kg-1 (i.e., +79 and +95%), under rainfed and irrigated conditions, respectively, during 2025-2035. Overall, these results demonstrated that sown alfalfa pasture on marginal lands represents an effective grassland conservation pathway over the short- to medium-term time horizon based on current technologies.

High-resolution tracking data highlight the importance of fallow land during a seasonal habitat bottleneck for a steppe-land specialist

Farmland ecosystems are seasonally dynamic habitats shaped by meteorological fluctuations and anthropogenic land-use changes. Farmland birds may be seasonally constrained with limited foraging and breeding resources (so-called “resource bottlenecks”), especially when there is a loss of natural and semi-natural habitats. During spring, the growth of cereal crops makes a large proportion of arable land unsuitable for specialist steppe birds with narrow vegetation structure requirements. We investigated the existence of a seasonal bottleneck of suitable habitats for steppe birds using the endangered Pin-tailed sandgrouse (Pterocles alchata) as a model species. We used for first time lightweight GPS tags to study habitat selection and movement patterns throughout the cereal crop cycle during three years in north-eastern Spain. We also evaluated if conservation measures promoting suitable vegetation structures for steppe birds (Targeted Fallow Management, TFM) influenced habitat selection. Sandgrouse avoided cereal crops when cereal vegetation was high, resulting in a 30% reduction of suitable habitat area at the start of the breeding season. This proved the existence of a spring habitat bottleneck when sandgrouse only selected open natural habitats and fallows. Sandgrouse similarly selected TFM and conventionally managed fallows during and after the bottleneck, possibly because of their similar vegetation structure and the scarcity of alternative suitable habitats. Halting the ongoing loss of fallow land is paramount for the conservation of steppe birds like sandgrouse because they constitute a key refuge to buffer the impacts of seasonal habitat bottlenecks.

Soil bacterial community responses to land-use change in Mollisol of Northeast China

An important sensitive indicator responding to land-use change is the microbial community, which has been recently shown to directly influence soil health and function. Here, we investigated the impact of different land use on the soil bacterial community composition. A field experiment was carried out to check the changes of bacterial communities in response to maize cropping and fallow using Illumina MiSeq sequencing method. Compared to the referred natural grassland, 8- and 100-year maize cropping led to significant changes in the relative abundances of 5 and 15 genera, respectively, while 8-year fallow changed the relative abundances of 11 genera. These changed genera resulted in distinct clustering of soil bacterial communities across land-use change according to principal coordinate analysis (PCoA). The bacterial community was far away from referred natural grassland with extension of maize cropping, and which derived by fallow was close to natural grassland. Based on RDA analysis, the major contributors from soil chemical properties to grassland samples were pH, TC, TN, MBC and MBN. ConclusionsThese differential responses of bacterial genera are illustrative of the susceptibility of bacterial community to land-use change and given recovery possibility of bacterial community structure via appropriate fallow management associated with improving soil chemical property.

Assessing water quality for cropping management practices: A new approach for dissolved inorganic nitrogen discharged to the Great Barrier Reef

Applications of nitrogen (N) fertiliser to agricultural lands impact many marine and aquatic ecosystems, and improved N fertiliser management is needed to reduce these water quality impacts. Government policies need information on water quality and risk associated with improved practices to evaluate the benefits of their adoption. Policies protecting Great Barrier Reef (GBR) ecosystems are an example of this situation. We developed a simple metric for assessing the risk of N discharge from sugarcane cropping, the biggest contributor of dissolved inorganic N to the GBR. The metric, termed NiLRI, is the ratio of N fertiliser applied to crops and the cane yield achieved (i.e. kg N (t cane)−1). We defined seven classes of water quality risk using NiLRI values derived from first principles reasoning. NiLRI values calculated from (1) results of historical field experiments and (2) survey data on the management of 170,177 ha (or 53%) of commercial sugarcane cropping were compared to the classes. The NiLRI values in both the experiments and commercial crops fell into all seven classes, showing that the classes were both biophysically sensible (c.f. the experiments) and relevant to farmers’ experience. We then used machine learning to explore the association between crop management practices recorded in the surveys and associated NiLRI values. Practices that most influenced NiLRI values had little apparent direct impact on N management. They included improving fallow management and reducing tillage and compaction, practices that have been promoted for production rather than N discharge benefits. The study not only provides a metric for the change in N water quality risk resulting from adoption of improved practices, it also gives the first clear empirical evidence of the agronomic practices that could be promoted to reduce water quality risk while maintaining or improving yields of sugarcane crops grown in catchments adjacent to the GBR. Our approach has relevance to assessing the environmental risk of N fertiliser management in other countries and cropping systems.

Coupled forest zoning and agricultural intervention yields conflicting outcomes for tropical forest conservation in the Democratic Republic of the Congo (DRC)

Agricultural intensification and forest conservation are often seen as incompatible. Agricultural interventions can help boost food security for poor rural communities but in certain cases can exacerbate deforestation, known as the rebound effect. We tested whether coupling agricultural interventions with participatory forest zoning could improve food security and promote forest conservation in the Democratic Republic of the Congo. Simple agricultural interventions led to a >60% increase in cassava yields and a spill-over effect of improved cassava variety uptake in non-intervention zones. Household surveys conducted at the end of the 8 year project implementation period revealed that households that received agricultural interventions had more favorable attitudes toward forest zoning and conservation. The surveys also showed that farmers in the intervention domain practiced less land-intensive field and fallow management strategies compared to those practiced in the non-intervention domain. However, an 18 year time series analysis of Landsat satellite data revealed that agricultural expansion persisted in areas both with and without intervention assistance, and there is risk of a rebound effect. Approximately 70% of the tree cover loss that occurred outside of the agricultural areas was located within a 3 km buffer zone surrounding the outermost edges of the agricultural areas, which suggested that the majority of tree cover loss was caused by agricultural expansion. Within that 3 km buffer, average annual tree cover loss during the post-intervention period was higher in the intervention domain compared to the non-intervention domain (0.17% yr−1 compared to 0.11% yr−1 respectively, p < 0.001), suggesting risk of a rebound effect. The disconnection between household perceptions of zoning adherence and actual behavior indicates the importance of strengthening governance structures for community-based monitoring and enforcement.

Ten years of monitoring dissolved inorganic nitrogen in runoff from sugarcane informs development of a modelling algorithm to prioritise organic and inorganic nutrient management

Reducing nitrogen (N) losses from cropping systems to aquatic ecosystems is a global priority. In Australia, N losses from sugarcane production in catchments adjacent to the Great Barrier Reef (GBR) are threatening the health of this World Heritage-listed coral reef ecosystem. N losses from sugarcane can be reduced by improving fertiliser management. However, little is known about the contribution of organic sources of N, such as mill mud. We used more than 10 years of data from two of the main Australian sugarcane regions, a high (Wet Tropics) and moderate (Mackay Whitsundays) rainfall area, to calibrate and validate a model to predict dissolved inorganic nitrogen (DIN) losses in runoff from both inorganic and organic fertilisers. DIN losses in runoff were well simulated (RMSE = 0.37 and 2.0 kg N ha−1 for the Wet Tropics and Mackay Whitsunday regions, respectively). Long-term simulations of rate and fertiliser deductions to account for N from organic sources showed that adopting best management practices for organic fertiliser (applying ≤50 wet t ha−1 mill mud) can significantly reduce DIN in runoff losses compared with applications of 150 wet t ha−1. Simulations of typical farmer practices in relation to fallow management (bare fallow vs. legume fallow) and organic fertiliser placement (buried in a fallow but surface applied to a green cane trash blanket in ratoons) showed that inorganic fertiliser rates need to be adjusted to account for N inputs from both mill mud and legume crops. Rates of application of organic N had a larger impact on DIN runoff losses than placement or timing of application. This work presents a DIN in runoff modelling algorithm that can be coupled with nitrogen models readily available in agricultural models to assess the impact of nutrient management on the quality of water leaving agricultural systems.

Assessment of aggregate stability and soil organic carbon sequestration in Alfisols of Guinea Savanna

Soil aggregate stability is a vital indicator for improving soil quality and controlling soil losses. This study aimed to assess the effect of fallow forage legumes and fertilizer application on wet and dry stability aggregate and soil organic carbon on Alfisols of Guinea Savanna, Nigeria. The study was conducted at the Institute for Agricultural Research (IAR) experimental field, Samaru Zaria. Treatment consisted of 3 plots (Centrosema pascuorum (Cp planted), Macrotyloma uniflorum (Mu planted) and control-natural vegetation regrowth). The soil samples collected were dried at room temperature and then separated into six aggregate fractions. Aggregate stability assessment results showed that dry stable aggregate fraction was significantly influenced by fallow management practice where Cp planted fallow recorded the highest amount in soil aggregate sizes of 2000 μm (0.99 g kg-1). Concerning wet stable aggregate, the proportion of 2000 μm sized aggregate fraction had the highest value (0.22 g kg-1) under treatment Cp. However, 0 kg N ha- 1 -1 produced the highest quantity in 2000 μm (0.23 g kg ) sized stable aggregates, and there was no significant difference in Nitrogen and Phosphorus application rates. The wet mean weight diameter (MWD) was significantly affected by forage legume with Mu planted fallow having the highest value (0.40 g kg-1) while the dry MWD aggregates with Cp recorded the best value (1.37 g kg-1). Cp planted fallow sequestered more carbon (0.65 g kg-1) in the 500 µm aggregates fraction. NVR contributed the highest carbon (0.80 g kg-1) under 50 µm sized aggregates. For carbon content in &lt;50 µm sized aggregates, Mu produced the highest carbon (0.72 g kg-1) in the fraction. Conclusively, the type of management practices affects the soil aggregation size fractions, which increased soil organic carbon sequestered.

Tree diversity, soil organic carbon lability and ecosystem carbon storage under a fallow age chronosequence in North East India

Shifting cultivation, the oldest farming system of the world and is the dominant land use in mountainous regions of South and Southeast Asia. North-East India (NEI) region, one of the world's biodiversity hotspots, covers 17.2 million ha of land under forests, constituting ~25% of India's total forest area. The population-driven abrupt decline of the fallow period's duration has aggravated soil erosion, depletion of nutrients, decreased productivity, reduced biodiversity, and weakening of essential ecosystem services. Therefore, the present research aims to explore whether the duration of the fallow period of up to 20-years can restore diversity of tree species, biomass carbon, and ecosystem carbon stock equivalent to those under natural forests. Based on the accessibility and availability of the fallow stands, three categories were selected for the study (1–2, 5–8, and 15–20 years), and these were replicated eight times for each age group. While the 20-years of fallow increased tree diversity, it was still 22% lower than that of the natural forest. Similarly, a 2.7-fold increase in biomass carbon storage was observed with an increase in the fallow period from 5–8-years (33.4 Mg ha −1 ) to 15–20-years (92.9 Mg ha −1 ), yet the latter was 40% lower than that under the natural forests. The very labile and labile carbon stocks decreased with increase in the fallow period. In contrast, the less labile and non-labile carbon stocks increased with increase in the fallow age. Because of the absence of a long fallow management system in the region, and to minimize the risks of ecosystem carbon degradation, adopting an integrated approach is recommended to enhance the ecological integrity of the degraded lands under shifting cultivation while also improving the livelihood of the shifting cultivators. • Shifting cultivation dominates tropical to sub-tropical forest regions in North East India. • Shifting cultivation is a major driver of ecosystem C loss. • The 15-20-year-old fallow had more even distribution of tree species. • SOC: ecosystem C ratio was the highest under 1–2-year fallow. • 15–20-year fallow had 23% lower ecosystem C storage than natural forest.

Fallow management input strategies for weed management in Florida cabbage production.

Fallow period weed management is an important Florida production consideration due to its duration and impact on the cash crop. Cover cropping is a valuable summer fallow period option for weed suppression. Sorghum-sudangrass is a commonly used, competitive, and allelopathic Florida summer cover crop. The effect of increased seeding rate, a herbicide application, and added fertilizer inputs during the fallow period on the cover crop, weed populations, and cabbage yield was explored and compared to nontreated and chemical fallow controls. Increased sorghum-sudangrass seeding rates had no effect on the resultant stand density or biomass compared to the standard seeding rate. Cover cropping did not consistently suppress purple nutsedge, Florida pusley, or wild radish and added fertilizer inputs produced variable results. S-metolachlor enhanced purple nutsedge suppression at low densities but did not improve grass, wild radish, and Florida pusley suppression. Increased fallow management inputs did not consistently enhance weed suppression or provide benefit to the cash crop. Sorghum-sudangrass suppressed Poaceae densities during the fallow period but did not adequately suppress nutsedge, wild radish, or Florida pusley densities over time. We conclude that weed management inputs should be focused on the cash crop and that enhanced management during the fallow period has limited benefit. © 2021 Society of Chemical Industry.