Alley Cropping Research Articles

English

Organic amendments have been known to improve soil physical and chemical properties in sub-Saharan Africa. However, research information on how organic amendments affect aggregate stability and the degree of their effects in comparison to others is inadequate in Zambia. The study was carried out to assess the effect of organic amendments on soil dry aggregate stability and organic matter on soils from Chipata, Zambia. The specific objectives were to: Assess the effect of organic amendments on soil dry aggregate stability and assess if there is a relationship between soil organic matter and soil aggregate stability on a loamy ferric luvisol soil. Soil aggregates were collected from the top 10 cm of 10 m × 10 m plots in each treatment replicated five times. These aggregates were sieved through a 9.5 mm, and the retained aggregates on an 8 mm sieve were collected and used for aggregate stability analysis. Analysis of variance (ANOVA) of results showed significant differences among the means of five treatments: Sunn hemp, Tephrosia vogelii alley cropping, pigeon pea alley cropping, animal manure, and conventional treatments on a loamy ferric luvisol. Amending soils with Sunn hemp showed a significantly higher mean weight diameter (MWDd) of 2.393 compared to amending soils with T. vogelii alley cropping MWDd 1.767 (P value <0.001). Hence, for a loamy ferric luvisol soil, Sunn hemp and animal manure may be used to improve the condition especially for aeration and aggregate stability. Key words:  Tephrosia vogeli, Sunn hemp, animal manure, conventional, loamy ferric luvisol.

Energy balance and greenhouse gas emissions in an agroforestry system - a case study from Eastern Germany

ABSTRACT Following a cradle-to-farm-gate approach, we determined the input of fossil energy and greenhouse gas emissions (GGE) for conventional and agroforestry land use on a farm in a low profit region of Germany. On the basis of a calculation model with a recurring crop rotation of maize, rye, oat, and a catch crop mixture, it was found that a short rotation alley cropping system (SRACS) with a 10% (A10) and a 40% (A40) tree area for bioenergy production consumed 7% and 32% less fossil energy than the conventionally managed site (C). Simultaneously, the net energy gains and energy efficiency of the plant production process were increased by up to 8 and 53%, respectively. Likewise, the operational GGE accumulated to 3.1 Mg ha−1 yr−1 under C farming and could be reduced by 9% and 36% in A10 and A40, respectively. Overall, a multidimensional land use indicator comparison proved that under specific site conditions agroforestry land use can increase the energy output per unit of land area, while the energy input and GGE per metric ton of biomass yield were considerably lower than in C farming. Nominal range sensitivity analysis revealed that the energetic and ecological performance of the system was highly sensitive to the size and productivity of the tree area as well as to the use of fertilisers. Our findings suggest that SRACS may fundamentally improve the environmental and energetic performance of the cultivation process on marginal land, without leading to substantial losses in agricultural livestock production area.

Evaluating a trait-based approach to compare natural enemy and pest communities in agroforestry vs. arable systems.

Diversified farming systems, for example those that incorporate agroforestry elements, have been proposed as a solution that could maintain and improve multiple ecosystem services. However, habitat diversification in and around arable fields has complex and inconsistent effects on invertebrate crop pests and their natural enemies. This hinders the development of policy recommendations to promote the adoption of such management strategies for the provision of natural pest control services. Here, for the first time, we conducted a trait-based approach to investigate the effect of farming system on plant, invertebrate herbivore, and invertebrate natural enemy communities. We then evaluated this approach by comparing the results to those generated using a traditional taxonomic approach. At each of three working farms, we sampled within an agroforestry field (a diverse farming system comprising alleys of arable crops separated by tree rows), and within a paired non-diversified area of the farm (arable control field). Each of 96 sample points was sampled between 8 and 10 times, yielding 393,318 invertebrate specimens from 344 taxonomic groups. Diet specialization or granivory, lack of a pupal stage, and wing traits in invertebrates, along with late flowering, short flowering duration, creeping habit, and perenniality in plants, were traits more strongly associated with agroforestry crop alleys than the arable control fields. We hypothesize that this is a result of reduced habitat disturbance and increased habitat complexity in the agroforestry system. Taxonomic richness and diversity were higher in the agroforestry crop alleys compared to the arable control fields, but these effects were stronger at lower trophic levels. However, functional trait diversity of natural enemies was significantly higher in the agroforestry crop alleys than the arable control fields, suggesting an improved level of biocontrol, which was not detected by traditional diversity metrics. Of eight key pest taxa, three were significantly suppressed in the agroforestry system, while two were more abundant, compared to the arable control fields. Trait-based approaches can provide a better mechanistic understanding of farming system effects on pests and their natural enemies, therefore we recommend their application and testing in future studies of diversified farming systems.

Which Socio-economic Conditions Drive the Selection of Agroforestry at the Forest Frontier?

Models are essential to assess the socio-economic credentials of new agroforestry systems. In this study, we showcase robust optimisation as a tool to evaluate agroforestry’s potential to meet farmers’ multiple goals. Our modelling approach has three parts. First, we use a discrete land-use model to evaluate two agroforestry systems (alley cropping and silvopasture) and conventional land uses against five socio-economic objectives, focusing on the forest frontier in eastern Panama. Next, we couple the land-use model with robust optimisation, to determine the mix of land uses (farm portfolio) that minimises trade-offs between the five objectives. Here we consider uncertainty to simulate the land-use decisions of a risk-averse farmer. Finally, we assess how the type and amount of agroforestry included in the optimal land-use portfolio changes under different environmental, socio-economic and political scenarios, to explore the conditions that may make agroforestry more attractive for farmers. We identify silvopasture as a promising land use for meeting farmers’ goals, especially for farms with less productive soils. The additional labour demand compared to conventional pasture, however, may prove an important barrier to adoption for farms facing acute labour shortages. The selection of agroforestry responded strongly to changes in investment costs and timber prices, suggesting that cost-sharing arrangements and tax incentives could be effective strategies to enhance adoption. We found alley cropping to be less compatible with farmers’ risk aversion, but this agroforestry system may still be a desirable complement to the land-use portfolio, especially for farmers who are more profit-oriented and tolerant of risk.

Tree rows in temperate agroforestry croplands alter the composition of soil bacterial communities

BackgroundTree-based intercropping (agroforestry) has been advocated to reduce adverse environmental impacts of conventional arable cropping. Modern agroforestry systems in the temperate zone are alley-cropping systems that combine rows of fast-growing trees with rows of arable crops. Soil microbial communities in these systems have been investigated intensively; however, molecular studies with high taxonomical resolution are scarce.MethodsHere, we assessed the effect of temperate agroforestry on the abundance, diversity and composition of soil bacterial communities at three paired poplar-based alley cropping and conventional monoculture cropland systems using real-time PCR and Illumina sequencing of bacterial 16S rRNA genes. Two of the three systems grew summer barley (Hordeum vulgare); one system grew maize (Zea mays) in the sampling year. To capture the spatial heterogeneity induced by the tree rows, soil samples in the agroforestry systems were collected along transects spanning from the centre of the tree rows to the centre of the agroforestry crop rows.ResultsTree rows of temperate agroforestry systems increased the abundance of soil bacteria while their alpha diversity remained largely unaffected. The composition of the bacterial communities in tree rows differed from those in arable land (crop rows of the agroforestry systems and conventional monoculture croplands). Several bacterial groups in soil showed strong association with either tree rows or arable land, revealing that the introduction of trees into arable land through agroforestry is accompanied by the introduction of a tree row-associated microbiome.ConclusionThe presence of tree row-associated bacteria in agroforestry increases the overall microbial diversity of the system. We speculate that the increase in biodiversity is accompanied by functional diversification. Differences in plant-derived nutrients (root exudates and tree litter) and management practices (fertilization and tillage) likely account for the differences between bacterial communities of tree rows and arable land in agroforestry systems.

High Stem Count: A Negative Morphological Growth Parameter in Irish Potato (Solanum Tuberosum l.) Production

Indubitably, some morphological parameters contribute positively to Irish potato (Solanum tuberosum Lin.) yield in terms of their high values (numbers) but conversely, increase in stem count (number of stems stand-1) brings about decrease in potato yield. This phenomenon was investigated during a three-year study on potato production under alley cropping system in both rain-fed and irrigated cropping seasons. In carrying out this experiment, completely randomized block design comprising 5 treatments and 3 replicates for 5 cropping seasons was employed. Treatments included different levels of Albizia lebbeck green manure application with or without its hedge rows (commencing with 6 months’ old saplings) and the control. Results showed significant effect of stem count on yield (at P<0.05) sequel to smaller sizes of tubers from numerous stems stand-1 which led to low tuber weight/yield (potato being a stem tuber). Simple correlation matrix between stem count and yield was negative and significant (r=-0.891, P<0.05) at rain-fed cropping season, bivariate and multiple correlation / regression analyses of growth parameters versus yield indicated negative relationship of stem count with yield (r = -0.891, R2 = 0.794, P < 0.05) in rain-fed cropping seasons as opposed to irrigated cropping season which were not significantly different. Thus, the correlation between stem count and tuber count was positive but negative with yield (the higher the number of stems stand-1 the more the smaller potato tubers especially in treatments with low nutrient status) the lower the yield.

Spatial arrangement in alley cropping of moringa and crops to optimize farming income on small Potteran Island, Sumenep Regency

Research on alley cropping was conducted as it contributes to soil and water conservation, in addition to improves landscapes aesthetics. This cropping system was introduced to farmers in the small island of Poteran, Sumenep Regency. Farmers on this island generally have narrow land and limited capital, hence intensification of farming with small capital but maximum production and income is needed. In an effort to obtain a high income, it is necessary to find the optimal spatial arrangement between hedgerowspace and alley crops space. The spatial planning model reserached included three scenarios, i.e. two row, three row and four row moringa hedge crop by combining corn, peanut, and cassava as alley crops.To obtain optimal scenario, this research used alley cropping data from previous research conducted in Talango Village, Poteran Island, on an area of 0.16 ha. Subsequently, a linear program supported by a solver application in Microsoft Excel was used to determine the optimum spatial arrangement scenario. The results showed a two-row moringa scenario with cassava as alley crop produced the highest income with the lowest cost.

Assessment of Farmer’s Perception and Adoption of Agroforestry Practices: The Case of Assosa District, Western Ethiopia

Agroforestry is a sustainable land management system which integrate production of crops, forest trees and animals at the same time on the same unit of land and put on management practices that are friendly with local population. Population growth and continuous use of agricultural land are the major causes of soil fertility reduction in rural Ethiopia and also in the study area. Existing land suitable for agriculture or crop production, grazing or forestry is decreasing while human populations are gradually increasing. As the population continues to grow, the gap between supply and demand for agricultural land continues to expand. Such a situation is leading to severe land use conflicts between the crop production and other type of land use such condition leading to reduction of 4 agroforestry practice. Despite this, one of the solutions to meet diverse people’s requirement with fixed land is through the application of agroforestry which is more advantageous than mono cropping. Agroforestry practices play important role so in order to strengthen and make the existing practice effective. This study was conducted to assess adoption of agroforestry practices in assosa woreda. The collected data were analyzed using descriptive statistics. The results showed that most of the sampled house hold heads 89 (64.5%) are not practicing agroforestry technology in the study area. Some of the major Agroforesty practices that have been commonly implemented include alley cropping, homegardens, and tree on crop land. The attitude of farmers towards agroforestry practice is positive and is well understood that agroforestry increase farm income, soil fertility, decreased complete crop failure and helping resolving fuel wood demands. Agroforestry technologies are not very well practiced so far in Assosa destrict due to different reasons. The government and other concerned organization should try to reduce the independent factors that affect adoption of agroforestry practice significantly through providing the necessary materials and creating awareness to farmers.

Biomass Performance and Competition Effects in an Established Temperate Agroforestry System of Willow and Grassland—Results of the 2nd Rotation

Agroforestry systems (AFSs) are promoted as environmentally friendly and climate-change-resilient cultivation systems with the potential of increasing ecosystem services. Especially under temperate climatic conditions, the implementation in agricultural practice is low so far, inter alia due to the lack of knowledge regarding longer-term effects of such systems. This study investigated biomass yields and crop development during the second rotation of an alley cropping system with willows (clone “Tordis” ((Salix schwerinii x S. viminalis) x S. vim.)) and grassland that was established in March 2011, as reported in a former study of the authors. Two grassland swards (white clover grass (Lolium perenne L. and Trifolium repens L.) (CG) and a diversity mixture with 32 plant species (DIV)) were proven in an intensive (3/4 cuts per year) and extensive management system (two cuts per year). Total yield (sum of three years) of AFS increased substantially in the second rotation (year four to six after establishment of the AFS). This was particularly due to a fivefold increase in woody biomass. At the same time, yields of grassland biomass decreased slightly. Biomass of CG outperformed DIV, especially in the intensive managed systems with a dry matter (DM) yield of 18 t ha−1, compared to 12.6 t ha−1. However, AFS grassland yields were always lower than yields of reference areas with grassland in pure stand. Nevertheless, lower yields are probably caused by competition effects between woody crops and grassland. Grassland yields along transects across the grassland alleyways showed a strong decrease in the border areas in all treatments. Higher grassland yields in the alley center did not compensate yield reductions in border areas. Furthermore, the botanical composition of grassland was modified in border areas with reduced legume DM contribution and increases of both grasses and forbs. Thus, the width of grassland alleys with 9 m caused strong competition effects by the willows.

Factors influencing German farmer’s decision to grow alley cropping systems as ecological focus areas: a regression analysis

The cultivation of alley cropping agricultural wood is an opportunity to comply with the greening requirements of the common agricultural policy (CAP; 2014-2020), but farmers are not permitted to display the whole alley cropping system (ACS) as ecological focus area (EFA) in Germany. They can display the agricultural wood stripes separately as EFA instead. The willingness of farmers is of key importance for a successful establishment, but, so far, the acceptance of this greening measure is extremely low. The aim of this paper is therefore to point out factors which have linkages to the acceptance of ACS as EFAs by conducting an online survey among German conventional farmers. The results of the regression analysis show that factors such as attitude towards agricultural wood, level of professional education, location and social environment affect the acceptance of ACS as EFA. To conclude, starting points that promote this type of greening measure are identified.

Can different soil fertilization regimes modify soil fauna to interfere in maize grain yield?

Soil fauna activities transform the soil, but soil organisms are also influenced by changes in the land. We hypothesize that different soil fertilization regimes modify soil fauna and in this way affect maize grain yield. The aim of this study was to evaluate the effects of different soil fertilization regimes on the structure of the soil fauna and the association between these organisms and the maize grain yield. The experiment was conducted in Maranhão State (Brazil), in an alley crop system which was divided into 32 plots of 4×10 m, with four replicates and the following treatments: Gliricidia sepium – gliricidia (G), potassium (K), humic acid (HA), humic acid + potassium (HA + K), potassium + gliricidia (K + G), humic acid + potassium + gliricidia (HA + K + G), humic acid + gliricidia (HA + G) and uncovered soil (US). Soil fauna dominance, abundance, richness, Shannon–Wiener diversity index, and Pielou evenness index and maize grain yield were determined. Fertilization with humic acid and potassium caused the dominance of isopods. The dominance of ants was also related to soil potassium (K treatment). The only taxon associated with yield was Araneae. Although fauna abundance did not show differences between treatments, it was related to yield. This study does not confirm the hypothesis that different soil fertilization regimes affect soil fauna and consequently influence maize grain yield. Nevertheless, we confirm that maize grain yield may be improved by the presence of specific groups and by the increased abundance of soil fauna.

Sustainable land use options for optimum resources use in maize based cropping system on uplands of Western Thailand

Worldwide, soil degradation due to erosion is still a major issue. Minimum tillage, intercropping, and alley cropping are important features of conservation agriculture and food security, but the farming communities are reluctant to accept these practices due to area reduction and plant competition. We investigated maize sole cropping (T1) as current farmers’ practice; T2: maize intercropped with chilies, tillage and fertilization; T3: maize-chili intercrop, mini. tillage, fertilization, Jack-bean relay cropping; T4: Like T3 but with hedges; T5 and T6 like T3 and T4, respectively, but without fertilization on Thai uplands during 2010 and 2011. Maize above ground biomass (AGB) was higher in T2 than T1 during both years. Light use efficiency (LUE) for AGB was 1.44–1.56 and 1.44–1.96 g DM MJ−1 in T4 during 2010 and 2011, 17–47% higher than T1, respectively. Land equivalent ratio was 1.23 and 1.17 in T2 while 1.28 and 1.21 in T4 during 2010 and 2011, respectively. Maize grain nitrogen (Ng) was significantly lower in unfertilized treatments. Intercropping with soil conservation enhanced land use efficiency with soil protection against erosion. Understanding spatial variations of LUE, Ng, as well as their impact on crop productivity are useful for fine-tuning crop management in conservation agriculture and sustainable land use on uplands.

Under what management and policy scenarios can alley cropping be a competitive alternative in the United States Southeast?

Despite statements that it can mitigate financial risk through farm diversification, alley cropping in the United States Southeast has not been comprehensively modeled to estimate potential financial returns and risks. We used a Monte Carlo method to model stochastic financial returns to monocropping agriculture, loblolly pine plantation, and loblolly pine alley cropping in North Carolina, USA, plotting the results from 25,000 iterations to understand financial risk. Under certain scenarios and assumptions, alley cropping did have financial returns comparable to, or potentially higher than, monocropping agriculture, but did not lower overall risk, as measured by the spread of the distribution of financial returns. Pine plantations, on the other hand, did have lower risk than both alley cropping and monocropping. Alley cropping with wider 24.4-m alleys performed better than narrow 12.2-m alleys. Allowing the producer to choose a timber rotation length that optimizes financial returns generated the best financial returns for alley cropping, but this assumes perfect knowledge of the manager and is unrealistic. Current policy programs of government payments for commodity crops and cost-share for tree planting, tend to favor monocropping over alley cropping or pine plantation. A hypothetical system of payments for carbon sequestration does increase pine plantation and alley cropping financial returns, but not to the extent that commodity crop programs currently increase monocropping financial returns, and does not reduce risk significantly. Overall, on average agricultural land in North Carolina, alley cropping may be of value to certain producers, but we find those possibilities to be somewhat limited.

Litters effect on soil physicochemical and biological processes

The present study was carried out during 2016-17 to 2018-19 at All India Coordinated Research Project on Agroforestry under Dr DBSKKV, Dapoli, Maharashtra on Assessment of decomposition dynamics, microbial community and soil fertility under different trees in Alfisol. The 10 years old six tree species, viz. Gmelina arborea, Terminalia tomentosa, Acacia mangium, Gliricidia sepium, Acacia auriculiformis and Millettia pinnata blocks were framed in a randomized block design with four replications. Significantly (P>0.05) build-up of soil fertility, microbial community and enzymes assay were found due to incorporation of Gliricidia sepium and Millettia pinnata litters and also develops bio-stability in soil which helps to maintain soil fertility. The decompositions, 0-87.35% (weight loss) were recorded and overall decomposition dynamics of litters species in soil trend was, viz. T4>T6>T2>R1>T3>T5. Significantly higher improvement in microbial C: N ratio of soil was recorded by Gliricidia sepium (9.14) and Millettia pinnata (8.99). The higher microbial communities (bacteria, actinomycetes, fungi) and enzyme assay (dehydrogenase, acid and alkaline phosphatase activities) were recorded by Gliricidia sepium followed by Millettia pinnata which helps for developing biological fertility of soil. Most of the trees are nitrogen fixing species, the higher development and restoring of soil fertility by indigenous Gliricidia sepium and Millettia pinnata species and these species could be used to more suitable for looking block plantation, bund plantation, alley cropping, development of agroforestry and subsequently could be used as a source of nutrients by directly or in-situ litter decomposition in soil in a Tropical Zone.

Promoting generalist predators of crop pests in alley cropping agroforestry fields: Farming system matters

Developing agroecological practices that enhance biological control of crop pests is a major issue for the transition of agriculture towards sustainable and biodiversity-friendly systems. Agroecological infrastructures (AEI) are devoted to the support of ecosystem service providers, although they have mixed effects on natural enemies of crop pests. In temperate regions, alley cropping agroforestry involves within-field AEI, in the form of tree rows and associated understory vegetation strips. The objective of this study was to assess the potential of generalist predators (carabid beetles and cursorial spiders) to control weed seeds and invertebrate pests in alley cropping vs pure crop systems, under two contrasting farming systems (conventional vs organic). Predator surveys were carried out in May and June 2017 in South-Western France over 12 winter cereal fields. Our study revealed that the effect of alley cropping was modulated by the farming system. Under conventional farming, alley cropping had a negative effect on the activity-density and species richness of generalist predators, especially regarding carnivorous carabids whose activity-density was reduced by nearly 50%. Under organic farming, alley cropping enhanced both the activity-density and complementarity of generalist predators, with a two-fold increase in the activity-density of seed-feeding carabids (predominantly granivorous and omnivorous), potentially promoting weed seed and invertebrate pest control. Our results suggest that the effectiveness of AEI in promoting natural enemies depends on the farming system at the field scale, which affects resource availability and determines spillover intensity between habitats. AEI are often perceived as sources of natural enemies. However, sink and retention effects (i.e. reduced or delayed spillover into crop fields due to higher attractiveness of AEI) should not be overlooked as they can explain the mixed impacts of AEI on natural enemy communities.

Alley cropping as an alternative under changing climate and risk scenarios: A Monte-Carlo simulation approach

Alley cropping is an agroforestry system in which annual crops are grown in alleys between rows of woody perennials for timber or other products, which can provide ecosystem services and help farmers diversify outputs. But is alley cropping a financially viable alternative to monocropping? To answer this question, a Monte Carlo model of financial risk and returns was used to understand how this diversification of outputs might help farmers in the southeast United States adapt to future scenarios in which agriculture or forestry may become more risky due to a changing climate or other factors. Traditional monocropping had the highest mean returns in the base scenario (based on current risk conditions), but the highest risk. Pine plantations had the lowest returns and lowest risk, and alley cropping was intermediate (mean soil expectation values of $5513 for monocropping, $3955 for alley cropping, and $2693 for pine plantations). The model results showed that traditional monocropping does not stochastically dominate alley cropping in any of the risk scenarios, meaning that alley cropping may have a place for risk-averse farmers. Furthermore, in the scenario in which the downside risk of annual crop production is increased – perhaps due to increased frequency of floods, droughts, etc. – alley cropping mean returns are higher and risk lower than traditional monocropping (mean soil expectation values of $2951 and $2911, respectively, and pine plantations at $2688), meaning any risk averse farmer might prefer alley cropping to monocropping.

Dinamika Sistem Berbagi Sumberdaya (Resouces Sharing) Dalam Agroforestri: Dasar Pertimbangan Penyusunan Strategi Silvikultur

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Alley cropping systems as Ecological Focus Areas: A PLS-analysis of German farmers’ acceptance behaviour

“Greening”, which was introduced during the last reform of the Common Agricultural Policy, targets the enhancement of ecological sustainability in European agriculture. Due to its association with such sustainability gains, growing agricultural wood, either as short rotation coppices or as agroforestry systems using for example the alley cropping system method, is one option to fulfil the Greening requirement of providing Ecological Focus Areas. However, agricultural wood in general or as an Ecological Focus Area is still of only minor relevance in most European countries. Particularly in Germany, where farmers are nowadays increasingly confronted with a conflict between the goals of realising their own profits and meeting societies’ sustainability expectations, alley cropping systems are grown on a few field trials only. Reasons can likely be found in national specificities of political support for alley cropping systems as Ecological Focus Areas and in psycho-economic determinants of farmers’ acceptance; an under-researched topic so far. To close this research gap, this study aims at identifying determinants of farmers’ acceptance of alley cropping systems as Ecological Focus Areas. The conceptual framework developed is based on the Technology Acceptance Model 2. Survey data from 238 German farmers were collected and analysed by means of Partial-Least-Squares estimation. The results show that farmers’ experience with alley cropping systems as Ecological Focus Areas is rather low but they generally consider agricultural wood as useful in fulfilling Greening requirements. The intention to grow is explained by 44% of the model and actual growing behaviour by 48%. The perceived cost-usefulness-ratio, stakeholder influences and expected image effects are identified as the main drivers of farmers’ acceptance of alley cropping systems as Ecological Focus Areas. Based on these results, important implications are derived, to address to politicians, agricultural consultants, chambers of agriculture or farmers’ associations.

Carbon Budget of an Agroforestry System after Being Converted from a Poplar Short Rotation Coppice

Poplar (Populus L. spp.) Short Rotation Coppice systems (SRCs) for bioenergy production are being converted back to arable land. Transitioning to Alley Cropping Systems (ACSs) could be a suitable strategy for integrating former tree rows and arable crops. A field trial (Pisa, Central Italy) was set up with the aim of assessing the C storage of an ACS system based on hybrid poplar and sorghum (Sorghum bicolor L. Moench) and comparing it with that of an SRC cultivation system. The carbon budget at the agroecosystem scale was assessed in the first year of the transition using the net biome production (NBP) approach with a simplified method. The overall NBP for the SRC was positive (96 ± 40 g C m−2 year−1), highlighting that the system was a net carbon sink (i.e., NBP > 0). However, the ACS registered a net C loss (i.e., NBP < 0), since the NBP was −93 ± 56 g C m−2 year−1. In the first year of the transition, converting the SRC into an ACS counteracted the potential beneficial effect of C storage in tree belowground biomass due to the high heterotrophic respiration rate recorded in the ACS, which was fostered by the incorporation of residues and tillage disturbance in the alley. Additional years of heterotrophic respiration measurements could allow for an estimate of the speed and extent of C losses.

Alley cropping affects perennial bioenergy crop root distribution, carbon, and nutrient stocks

AbstractThis study quantified root biomass distribution; root accrual of C, N, P, and K; and changes in soil organic carbon (SOC) associated with alley‐cropped switchgrass (Panicum virgatum L.), prairie cordgrass (Spartina pectinata Bosc ex Link), intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth and Dewey ‘Rush’], and a native polyculture planted between rows of ‘NM6’ poplar (Populus maximowiczii × P. nigra) and ‘Fish Creek’ willow (Salix purpurea) at two Minnesota sites (Empire and Granada). After 4 yr since establishment, SOC declined at each site but was not influenced by species selection. NM6 poplar–prairie cordgrass systems had among the highest root biomass, C, and nutrient accrual, with up to 16.3 Mg root biomass, 7.0 Mg C, 175 kg N, 31 kg P, and 97 kg K ha−1. Fine roots were the largest fraction of belowground biomass, although course roots were also a large fraction for poplar and prairie cordgrass. Tree roots extended to 6 m into the crop alley, although 85–89% were within 1 m of tree rows, depending on tree species. Crop fine root biomass was reduced up to 67% at 1 m from tree rows and 20% at 3.5 m and was up to 142% greater in willow than in poplar alleys. Total root C was predominated by poplars at Empire regardless of herbaceous crop type, whereas the proportions of tree and crop root C varied by crop at Granada. These results suggest that prairie cordgrass is well suited to alley cropping and that, due to the competitive ability of poplars, productivity, C sequestration, and nutrient accrual may be greater in willow systems in the long term.