Alwyn Williams

Soil Functional Zone Management: A Vehicle for Enhancing Production and Soil Ecosystem Services in Row-Crop Agroecosystems.

There is increasing global demand for food, bioenergy feedstocks and a wide variety of bio-based products. In response, agriculture has advanced production, but is increasingly depleting soil regulating and supporting ecosystem services. New production systems have emerged, such as no-tillage, that can enhance soil services but may limit yields. Moving forward, agricultural systems must reduce trade-offs between production and soil services. Soil functional zone management (SFZM) is a novel strategy for developing sustainable production systems that attempts to integrate the benefits of conventional, intensive agriculture, and no-tillage. SFZM creates distinct functional zones within crop row and inter-row spaces. By incorporating decimeter-scale spatial and temporal heterogeneity, SFZM attempts to foster greater soil biodiversity and integrate complementary soil processes at the sub-field level. Such integration maximizes soil services by creating zones of ‘active turnover’, optimized for crop growth and yield (provisioning services); and adjacent zones of ‘soil building’, that promote soil structure development, carbon storage, and moisture regulation (regulating and supporting services). These zones allow SFZM to secure existing agricultural productivity while avoiding or minimizing trade-offs with soil ecosystem services. Moreover, the specific properties of SFZM may enable sustainable increases in provisioning services via temporal intensification (expanding the portion of the year during which harvestable crops are grown). We present a conceptual model of ‘virtuous cycles’, illustrating how increases in crop yields within SFZM systems could create self-reinforcing feedback processes with desirable effects, including mitigation of trade-offs between yield maximization and soil ecosystem services. Through the creation of functionally distinct but interacting zones, SFZM may provide a vehicle for optimizing the delivery of multiple goods and services in agricultural systems, allowing sustainable temporal intensification while protecting and enhancing soil functioning.

Different arbuscular mycorrhizae and competition with an exotic grass affect the growth of Podocarpus cunninghamii Colenso cuttings.

There is growing interest in the use of arbuscular mycorrhizal fungi (AMF) for ecological restoration. Numerous commercial AMF products are now available and are often used in preference to collecting indigenous AMF in treating restoration plants. Commercial AMF products are typically based on AMF strains exotic to the plant species and locations where they are used. We treated rooted cuttings of an endemic New Zealand tree species (Podocarpus cunninghamii) and an exotic and invasive grass (Agrostis capillaris) with an indigenous, pot-cultured AMF (Acaulospora laevis) and an exotic commercial AMF product (Glomus spp.). P. cunninghamii was grown in monoculture and together with A. capillaris, the latter to simulate field competition that often occurs in restoration plantings. In monoculture, the indigenous AMF resulted in significant increases in P. cunninghamii growth rates and tissue concentrations of both nitrogen and phosphorus. The commercial AMF had either no effect or a negative effect on P. cunninghamii growth and nutrient levels. A. capillaris growth and nutrient status were unaffected by the different AMF treatments. Competition eliminated any AMF benefit for P. cunninghamii. The results show that, for our chosen indigenous woody plant species, the commercially available AMF did not improve its early growth and nutrient acquisition in monoculture while, over the same period, the indigenous AMF induced positive growth and nutrient responses. These results have potential implications for forest restoration, particularly for nursery production of indigenous woody species.

Soil Water Holding Capacity Mitigates Downside Risk and Volatility in US Rainfed Maize: Time to Invest in Soil Organic Matter?

Yield stability is fundamental to global food security in the face of climate change, and better strategies are needed for buffering crop yields against increased weather variability. Regional- scale analyses of yield stability can support robust inferences about buffering strategies for widely-grown staple crops, but have not been accomplished. We present a novel analytical approach, synthesizing 2000–2014 data on weather and soil factors to quantify their impact on county-level maize yield stability in four US states that vary widely in these factors (Illinois, Michigan, Minnesota and Pennsylvania). Yield stability is quantified as both ‘downside risk’ (minimum yield potential, MYP) and ‘volatility’ (temporal yield variability). We show that excessive heat and drought decreased mean yields and yield stability, while higher precipitation increased stability. Soil water holding capacity strongly affected yield volatility in all four states, either directly (Minnesota and Pennsylvania) or indirectly, via its effects on MYP (Illinois and Michigan). We infer that factors contributing to soil water holding capacity can help buffer maize yields against variable weather. Given that soil water holding capacity responds (within limits) to agronomic management, our analysis highlights broadly relevant management strategies for buffering crop yields against climate variability, and informs region-specific strategies.

Different arbuscular mycorrhizal inoculants affect the growth and survival of Podocarpus cunninghamii restoration plantings in the Mackenzie Basin, New Zealand

Abstract There is increasing interest in the use of arbuscular mycorrhizal fungi (AMF) for ecological restoration, as AMF can improve plant nutrition and growth. However, some AMF can have negative effects on plant growth. It is therefore critical that restoration strategies incorporate appropriate AMF. This research investigated differences in growth and survival of Podocarpus cunninghamii (mountain tōtara) cuttings with six different AMF inoculums, with the aim of choosing the most appropriate mycorrhizal species for restoration success. Cuttings of P. cunninghamii were inoculated with AMF ranging from indigenous to exotic, including commercially available AMF and AMF isolated from remnant P. cunninghamii forest and ex-agricultural grassland. Plant growth and survival was compared after two seasons at a high country restoration site in the Mackenzie Basin. Plants treated with forest and indigenous AMF had significantly greater survival than those treated with commercial AMF. Forest AMF also resulted in significantly greater P. cunninghamii growth than all the other treatments. This has potentially important implications for restoration, as improved growth and survival of native woody species can improve restoration success by increasing establishment success and reducing management costs.

A regionally-adapted implementation of conservation agriculture delivers rapid improvements to soil properties associated with crop yield stability

Climate models predict increasing weather variability, with negative consequences for crop production. Conservation agriculture (CA) may enhance climate resilience by generating certain soil improvements. However, the rate at which these improvements accrue is unclear, and some evidence suggests CA can lower yields relative to conventional systems unless all three CA elements are implemented: reduced tillage, sustained soil cover, and crop rotational diversity. These cost-benefit issues are important considerations for potential adopters of CA. Given that CA can be implemented across a wide variety of regions and cropping systems, more detailed and mechanistic understanding is required on whether and how regionally-adapted CA can improve soil properties while minimizing potential negative crop yield impacts. Across four US states, we assessed short-term impacts of regionally-adapted CA systems on soil properties and explored linkages with maize and soybean yield stability. Structural equation modeling revealed increases in soil organic matter generated by cover cropping increased soil cation exchange capacity, which improved soybean yield stability. Cover cropping also enhanced maize minimum yield potential. Our results demonstrate individual CA elements can deliver rapid improvements in soil properties associated with crop yield stability, suggesting that regionally-adapted CA may play an important role in developing high-yielding, climate-resilient agricultural systems.

Confronting herbicide resistance with cooperative management: Confronting herbicide resistance with cooperative management

Abstract BACKGROUND Resistance of pathogens and pests to antibiotics and pesticides worldwide is rapidly reaching critical levels. The common‐pool‐resource nature of this problem (i.e. whereby the susceptibility to treatment of target organisms is a shared resource) has been largely overlooked. Using herbicide‐resistant weeds as a model system, we developed a discrete‐time landscape‐scale simulation to investigate how aggregating herbicide management strategies at different spatial scales from individual farms to larger cooperative structures affects the evolution of glyphosate resistance in common waterhemp (Amaranthus tuberculatus). RESULTS Our findings indicate that high‐efficacy herbicide management strategies practiced at the farm scale are insufficient to slow resistance evolution in A. tuberculatus. When best practices were aggregated at large spatial scales, resistance evolution was hindered; conversely, when poor management practices were aggregated, resistance was exacerbated. Tank mixture‐based strategies were more effective than rotation‐based strategies in most circumstances, while applying glyphosate alone resulted in the poorest outcomes. CONCLUSIONS Our findings highlight the importance of landscape‐scale cooperative management for confronting common‐pool‐resource resistance problems in weeds and other analogous systems.

A cooperative governance network for crop genome editing: The success of governance networks in other areas could help to find common ground for applying genome editing in agriculture

Emerging biotechnologies, such as genome editing, may revolutionize agricultural development through rapid and precise genetic manipulation of a wide range of crop traits without having to transfer foreign DNA [1]. If so, these new genetic‐engineering (GE) technologies can help to generate crop varieties to address critical challenges in agricultural development, such as climate resilience or nutrient uptake, or diet‐related problems in nutrition and health in poorer countries. However, society must also be protected from potential harmful effects of genetically manipulated crops on the environment, human health, or social welfare. Governance of these crops must therefore balance agricultural developments with risk assessment and prevention of potential harm. > …genome editing is being used to improve the characteristics of major crop plants, but the governance of crop genome editing is poorly defined and developed Presently, genome editing is being used to improve the characteristics of major crop plants, but the governance of crop genome editing is poorly defined and developed. Influential groups concerned with the potential hazards of such crops view this situation with growing alarm, which has created tensions with the academic community and regulatory agencies [2]. Both the USA and the European Commission are currently reviewing the governance of crops produced by genome editing and other new technologies. On the US side, at least, the review process appears unlikely to result in governance approaches that will satisfy parties that are concerned with either over‐ or under‐regulation of such crops, and tension and conflicts about them are likely to heighten. We propose an alternative approach for governance of these crops that may help to defuse tensions and enable exploration of genome editing technologies’ potential while protecting society from harm: a cooperative governance network. Such networks have performed well in …