Alley Cropping Agroforestry Research Articles

13 years of biomass production from three poplar clones in a temperate short-rotation alley cropping agroforestry system

Farmers' interest in establishing agroforestry systems is increasing, as they are considered to have many benefits, such as the possibility of climate adaptation and crop diversification. Growing wood on agricultural land can produce biomass for energy or material purpose. Knowledge of the yield potential of the woody component in an agroforestry system is essential for informed decision making by farmers. The present study investigates the biomass production of the three poplar clones 'Max 1′, 'Koreana' and 'Hybride 275′ during the first 13 years (2008–2021) of their growth in a short rotation alley-cropping agroforestry system in Lower Saxony, Germany, on a vertic cambisol as well as a stagnosol soil. There was a high clonal effect on re-sprouting and mortality of the trees as well as on the mean annual dry matter (DM) woody biomass increment (MAI). Overall, 'Max 1′ showed highest re-sprouting, lowest mortality and highest MAI compared to the clones 'Hybride 275′ and 'Koreana'. The MAI of the three poplar clones was not affected by the rotation length of 3 or 6 years. Over the period of 13 years MAI of 'Max 1′ was 13.3 t Mg ha−1 year−1 DM, whereas that of 'Hybride 275′ and 'Koreana' was 10.2 and 9.8 t Mg ha−1 year−1 DM, respectively. The MAI was significantly determined by the factor harvest year. A low MAI was found for the 3-year rotation cycle in 2021, which was most possibly caused by drier and warmer than average vegetation periods in 2018–2020. Under the given site conditions, clone 'Max 1′ proved to be the most productive.

Multifunctionality of temperate alley-cropping agroforestry outperforms open cropland and grassland

Intensively managed open croplands are highly productive but often have deleterious environmental impacts. Temperate agroforestry potentially improves ecosystem functions, although comprehensive analysis is lacking. Here, we measured primary data on 47 indicators of seven ecosystem functions in croplands and 16 indicators of four ecosystem functions in grasslands to assess how alley-cropping agroforestry performs compared to open cropland and grassland. Carbon sequestration, habitat for soil biological activity, and wind erosion resistance improved for cropland agroforestry (P ≤ 0.03) whereas only carbon sequestration improved for grassland agroforestry (P < 0.01). In cropland agroforestry, soil nutrient cycling, soil greenhouse gas abatement, and water regulation did not improve, due to customary high fertilization rates. Alley-cropping agroforestry increased multifunctionality, compared to open croplands. To ameliorate the environmental benefits of agroforestry, more efficient use of nutrients is required. Financial incentives should focus on conversion of open croplands to alley-cropping agroforestry and incorporate fertilizer management.

Wild herbaceous vegetation in agroforestry systems: an asset that should not be overlooked

Thanks to agroforestry, trees and hedgerows are back in numbers in agricultural landscapes, where they provide many services. Agroforestry also gives pride of place to wild herbaceous vegetation, often perceived as a constraint or neglected by humans. Omnipresent when the soil is not tilled, herbaceous vegetation grows spontaneously at the foot of trees. From alley-cropping agroforestry to bocage landscapes, these 'little' plants are proving to be a major asset for the agroecological transition. Through the presentation of key results, this article explains how to take advantage of the wild herbaceous vegetation in agroforestry systems, in order to conserve biodiversity and promote sustainable agricultural production

Digging deeper: microbial communities in subsoil are strongly promoted by trees in temperate agroforestry systems

AimsTemperate alley-cropping agroforestry systems maintain agricultural production while offering several environmental benefits. Central benefits of agroforestry systems such as the ‘safety-net’-role of the trees for leached nutrients are mainly due to processes occurring below the soil surface: the subsoil. Microorganisms in the subsoil may play a key role in the ‘safety-net’-function as they can improve the capturing and uptake of nutrients by the trees. Systematic investigations of microbial communities in temperate agroforestry systems, however, are restricted to topsoil.MethodsWe quantified bacteria, fungi, and functional groups of microorganisms in the topsoil and subsoil of two alley-cropping systems using real-time PCR. Topsoil and subsoil samples were collected in the tree rows and at multiple distances from the trees within the crop rows of the agroforestry systems as well as at an adjacent monoculture cropland.ResultsMicrobial population size decreased with soil depth likely due to limited resource availability in subsoil. Tree rows in agroforestry systems not only promote soil microbial populations in both the topsoil and subsoil but the promotion also extends gradually into the crop rows of the systems. The promotion of microorganisms through trees is stronger in subsoil than topsoil, pointing at more intense resource scarcity in the subsoil than topsoil.ConclusionsWe propose that tree root-derived resources and root litter, which are scarce in agricultural subsoils, triggered the strong positive response of the subsoil community to the trees. Finally, we provide initial evidence that subsoil microorganisms contribute to the ‘safety-net’-role of the trees in agroforestry systems.

Abundance, Diversity, and Function of Soil Microorganisms in Temperate Alley-Cropping Agroforestry Systems: A Review.

Modern temperate alley-cropping systems combine rows of trees with rows of crops (agroforestry), which allows for diverse interspecific interactions such as the complementary and competitive use of resources. The complementary use of resources between trees and crops is considered the main advantage of these multifunctional land use systems over cropland monocultures. Moreover, several studies demonstrated that agroforestry systems are environmentally more sustainable than cropland monocultures. Over two decades of research on soil microorganisms in temperate alley-cropping systems are characterized by a variety of different methodological approaches and study designs to investigate the impact of agroforestry on the soil microbiome. Here, we review the available literature on the abundance, diversity, and functionality of soil microorganisms in temperate alley-cropping systems. Further, we identify current knowledge gaps as well as important experimental factors to consider in future studies. Overall, we found that temperate alley-cropping systems increase soil microbial abundance, diversity, and functions as compared to cropland monocultures, which is expected to contribute to enhanced biological soil fertility in these systems.

Nutrient saturation of crop monocultures and agroforestry indicated by nutrient response efficiency

Efficient use of nutrients is a key requisite for a sustainable intensification of agriculture in order to meet the increasing global crop demand while minimizing deleterious environmental impacts. Agroforestry systems exhibit tree–crop interactions, which potentially contribute to nutrient-efficient agro-ecosystems. Our goal was to determine whether the conversion from cropland monocultures to alley-cropping agroforestry increases nutrient response efficiency (NRE), the ability of plants to convert available nutrients into biomass. We found that crop yield, plant-available nutrients and NRE were comparable between agroforestry and monocultures, but the trees in agroforestry had high NRE, contributing to nutrient retention of the agroforestry systems as a whole. The unimodal relationship of the crops’ NRE with plant-available nutrients suggests that NRE values were beyond optimum in both agroforestry and monoculture indicating nutrient saturation. This indicates that fertilizer inputs can be reduced (or optimized) without sacrificing crop yield or profit. Based on the NRE curves, we assessed that a reduction of plant-available N by 50% would lead to a decrease in crop yield by 17% and a concomitant increase in N response efficiency by 67%, whereas a similar reduction of plant-available P would lead to a decrease in crop yield by 8% with an increase in P response efficiency by 83%. An optimized fertilization to achieve such lower levels of plant-available nutrients will have beneficial effects on nutrient retention and redistribution. Optimizing fertilizer input will make alley-cropping agroforestry a productive and profitable agro-ecosystem that contributes to an ecologically sustainable agriculture.

Pesticide and Fertilizer Pollution Reduction in Two Alley Cropping Agroforestry Cultivating Systems

The efficiency of two common Mediterranean agroforestry systems, a potato-poplar and a maize-poplar, was assessed with respect to the uptake of nutrients and pesticides in an experimental plot located in Attica, Greece, during the cultivating period of 2016. Soil samples were collected on a monthly basis at different soil horizons and varying distance from the tree row. The monitored substances included all nitrogen ions (NO3−-N, NO2−-N, NH4+-N), phosphates (PO43−-P), potassium (K+), the insecticide chlorpyrifos, as well as the herbicides s-metolachlor, pendimethalin, and its metabolite M455H001. Experiments for the potato-poplar system exhibited reductions of more than 86% for K+, 90% for NO3−-N, 92% for NH4+-N, 85% for NO2−-N, and up to 100% for PO43−-P. Accordingly, for the maize-poplar system, reductions were more than 73% for K+, at least 77% for NO3−-N, approximately 77% for NO2−-N, 97% for NH4+-N, and up to 100% for PO43−-P. Regarding the examined pesticides, all substances reached more than 61.5% and up to 100% disappearance in the closest to the tree row points compared to the control points, thus also exhibiting the potential for tree uptake of the excess pesticides. As such, it was demonstrated that agroforestry alley cropping systems may act as a technique for pollution abatement, since tree roots that extend below the crops can uptake the excess of agrochemicals that would otherwise enter groundwater via leaching or surface water via runoff.

Influence of latitude on the light availability for intercrops in an agroforestry alley-cropping system

Light competition by trees is often regarded as a major limiting factor for crops in alley-cropping agroforestry. Northern latitude farmers are usually reluctant to adopt agroforestry as they fear that light competition will be fiercer in their conditions. We questioned the light availability for crops in alley-cropping at different latitudes from the tropic circle to the polar circle with a process-based 3D model of alley-cropping agroforestry. Two tree densities and two tree line orientations were considered. The effect of the latitude was evaluated with same-sized trees. The relative irradiance of the crops was computed for the whole year or at specific times of the year when crops need more light. The heterogeneity of crop irradiance across the alley was also computed. Surprisingly, crop relative irradiance of summer crops at high latitudes is high, at odds with farmers’ fears. Best designs were highlighted for improving the crop irradiance: North–South tree lines are recommended at high latitudes and East–West tree lines at low latitudes. At medium latitudes, North–South tree lines should be preferred to achieve an homogeneous irradiance of the crop in the alley. If we assume that trees at northern latitudes grow slower when compared to southern latitudes, then alley-cropping agroforestry is highly advisable even at high latitudes with summer crops.

Microbial communities and residues in robinia- and poplar-based alley-cropping systems under organic and integrated management

Organic farming and agroforestry are considered as sustainable alternative agricultural practices for intensive agriculture. In a long-term field trial in Scheyern Germany, we evaluated the effects of 21-year organic farming and 4-year agroforestry (robinia and poplar) on microbial community and microbial residues. Microbial biomass and microbial community were determined by fumigation–extraction method and the analysis of phospholipid fatty acid (PLFA), respectively. Microbial residues were evaluated by the measurement of amino sugars. The results showed that organic farming had significantly positive effect on soil organic carbon (SOC) but that it tended to decrease microbial biomass C (MBC), PLFA functional guilds, muramic acid (MurN), and glucosamine (GlcN). Robinia system, however, significantly increased SOC and had the potential to enhance MBC, PLFA functional guilds especially Gram (+), but it tended to decrease MurN and GlcN, in comparison with poplar system. The hedgerow tree did not show significantly positive effect on SOC and microbial properties except the abundance of fungi and Gram (+) bacterial, after 4-year establishment period. The principal component analysis of the PLFA profile showed that in comparison with other investigated treatments, robinia system under organic farming had significantly a different microbial community structure. It also indicated tree species-specific effect on microbial community in the organic farming was stronger than that in the integrated farming. In summary, the short-term introduction of trees into an existing agricultural system will not substantially change the microbial biomass, but it has certain influence on the abundance of specific microbial groups in the hedgerow. Although organic farming did not show positive effect on overall microbial indices, we still see positive effect on SOC after 21-year organic farming and its additive effect with robinia on SOC in current study. We expect that alley-cropping agroforestry system that combines organic farming and robinia hedgerow has a great potential for sequestering SOC and developing sustainable agroecosystems with time.

Productivity of poplar short rotation coppice in an alley-cropping agroforestry system

In temperate regions, short rotation woody crops cultivated as tree strips in alley-cropping agroforestry systems (ACS) can provide economic benefits by producing an additional commodity, and environmental benefits, e.g., soil erosion control, protection against evaporation and increased biodiversity. Moreover, compared to agrisivilcutural systems incorporating noble trees, ACS with short rotation coppice (SRC)-strips provide periodically high energy outputs and could help to answer environment and energetic political objectives in Germany. However, limited data are available in such systems concerning biomass production of different strip designs. An ACS incorporating poplar SRC has been established near Braunschweig in Lower Saxony (Germany) in 2008. Two harvest cycles (a coppiced 3-year rotation cycle and a un-coppiced 6-year rotation cycle) and two strip designs (“SRC”: 6 poplar rows; “Combined”: 4 poplar rows and 1 aspen row in the centre) were compared. Diameters at breast height, tree heights, shoot numbers and mortality rates were measured to describe growth and estimate yield of outer and middle poplar rows within a tree strip. Concerning the 3-year rotation cycle, higher numbers of shoots per tree as well as higher biomass yields compared to the control field were measured in outer rows, both leeward and windward. With the 6-year rotation cycle, all leeward rows and the middle rows of the combined design showed larger diameters and higher biomass yields. Middle rows of the SRC design, in both rotation cycles, revealed a quicker height growth than outer rows, but a reduced biomass production. Both rotation cycles showed similar yearly biomass production. The results can contribute to improve the design of poplar SRC-strips in ACS in order to optimize biomass production. We recommend reducing the number of rows within SRC-strips, while increasing their total length. Further research is however needed to determine effects of increased biomass in outer tree rows on adjacent crop fields, which influences the whole system productivity.

Soil Quality of a Mature Alley Cropping Agroforestry System in Temperate North America

Long-term effects of alley cropping on soils in the temperate zone are not widely known. Management, landscape, and soil depth effects on soil physical and biological properties were examined in a silver maple (Acer saccharinum L.) no-till corn (Zea mays L.)- soybean (Glycine max L.) rotation established in 1990 in northeast Missouri. Soils from crop alleys and tree rows were collected along transects traversing upper to lower landscape positions at three depths. Fluorescein diacetate hydrolase (FDA), β-glucosidase, β-glucosaminidase, and dehydrogenase activities were measured. Soil bulk density, aggregate stability, carbon (C), nitrogen N), and enzyme activities decreased with soil depth in alley and tree rows except for glucosaminidase. Soil physical and biological parameters did not differ significantly between alley and tree row. Landscape position effects were not significant for management or depth. Tree establishment improves soil quality in the crop alley as the system matures with improvements extended throughout the soil profile.

Decomposition of Erythrina poeppigiana leaves in 3-, 9-, and 18-year-old alleycropping systems in Costa Rica

Timing the application of organic residues and therefore the release of nutrients during decomposition may be critical to the growing crop in tropical alleycropping agroforestry systems. Field experiments were carried out in Turrialba, Costa Rica, to determine differences in Erythrina poeppigiana (Walp.) O.F. Cook leaf decomposition in 3, 9 and 18-year alleycropped agroforestry systems. Treatments consisted of mulch-only, and mulch plus Arachis pintoi Krapov. and W. Gregory var. CIAT 18347 in 3 and 9-year old alleycrops under no-till cultivation. The 18-year old site consisted of treatments with mulch-only and mulch plus chicken manure under disk plow cultivation. Litterbags, filled with E. poeppigiana leaves from 3, 9 and 18-year old trees, were placed on the soil surface and collected over a period of 84 days. Results showed no significant differences in the amount of plant residues remaining after 84 days in the 3-, 9-, and 18-year-old systems, or between the manure and mulch-only treatments. Comparing mulch-only treatments, leaves in the 18-year old system decomposed most rapidly which may be due to disk-plow cultivation practices where litterbags were in direct contact with the soil as opposed to the no-till system in the younger alleycrops.