Tree-based Intercropping Research Articles

Nitrogen leaching and soil nutrient supply vary spatially within a temperate tree-based intercropping system

Nitrogen leaching and soil nutrient supply vary spatially within a temperate tree-based intercropping system

Allometric equations for estimating aboveground biomass carbon in five tree species grown in an intercropping agroforestry system in southern Ontario, Canada

Allometric equations were developed for estimating aboveground biomass carbon (AGBC) in five tree species grown in a tree-based intercropping system at the University of Guelph Agroforestry Research Station, Guelph, Ontario, Canada. A total of 66 representative trees from five species: red oak (Quercus rubra) [n = 12], black walnut (Juglans nigra) [n = 16], black locust (Robinia pseudoacacia) [n = 10], white ash (Fraxinus americana) [n = 15], Norway spruce (Picea abies) [n = 13] were selected, harvested and their aboveground biomass and carbon content were quantified. Three commonly used allometric models were used to develop predictive equations. Regression models were developed and parameterized for each tree species and the best are presented based on information criteria (AIC, AICc, and BIC), mean absolute percentage error (MAPE), over/under estimation (MOUE), root mean square error (RMSE), R2, and regression coefficients (a, b) of the observed/predicted (OP) linear regression analysis. All equations with diameter at breast height (D) only and D and tree height (H) as the predictor variables fitted the AGBC data well, with R2 > 97% and RMSE < 40. However, a power model using D as the only predictor is recommended as the best model for black walnut, black locust, white ash, and Norway spruce. The models presented are the best fitted allometric equations for the indicated species and are recommended for these species, growing on similar soils under the same temperate conditions at densities of < 125 tree per hectare.

Production of sage, oregano and rosemary under shading conditions and the effects of light on growth and essential oil properties

Intercropping and agroforestry systems provide sustainable land and resource use efficiency, however, shading conditions generated by the base crop or tree cover is a restricting factor on the growth of the intercrop and productivity of the system. Hence, a two-year field experiment was carried out to assess the yield, essential oil properties, morphological changes, and anatomical adaptation of the shade-exposed sage (Salvia officinalis L.), oregano (Origanum onites L.) and rosemary (Rosmarinus officinalis L.) plants. Plant height, leaf area, chlorophyll content, herbage yield, essential oil content and biochemical profile of the selected species were comparatively examined under open-field, 40% and 75% shading conditions. Initially, after the seedlings were transplanted to the field, a horizontal growth of shaded plants, resulted in lower plant height, then, after the plants covered the soil surface, vertical growth was observed. Overall drug herbage yield decreased by 65% due to the shading treatments in the first year whereas rosemary, sage and oregano had 20.9%, 25.3% and 40.3% lower yields respectively in the second year. Average essential oil content of low-light exposed plants increased by 23% and 41% first and second year of the experiment, respectively. A negative linear relation between α-thujone content in essential oil of sage and shading level was recorded while in contrast, carvacrol content of oregano essential oil increased by shade treatment. The results concluded that herbage yield and quality properties of shaded plants were promising, especially after the first year, considering their potential in intercropping and agroforestry systems. Since the current study represented the results for artificial shading conditions, the tree-based intercropping studies needed to be performed with these species for the final conclusion.

Quantification of the Carbon Sequestration Potential of a 31-year-old Tree-based Intercropping System in Southern Ontario, Canada

Carbon (C) storage potential was quantified for four tree species which are commonly incorporated into tree-based intercropping (TBI) systems and compared with conventional agricultural systems in southern Ontario, Canada. In the 31-year-old TBI system at the University of Guelph’s Agroforestry Research Station, Norway spruce (&lt;em&gt;Picea abies&lt;/em&gt;), white cedar (&lt;em&gt;Thuja occidentalis&lt;/em&gt;), black walnut (&lt;em&gt;Juglans nigra&lt;/em&gt;) and red oak (&lt;em&gt;Quercus rubra&lt;/em&gt;) were planted in tree rows, intercropped with soybean (&lt;em&gt;Glycine max&lt;/em&gt;). In the conventional agricultural field, soybean was grown in a monocropping system. Above and belowground tree and crop C content, soil organic C (SOC) and system level C was quantified for each tree species as well as the conventional agricultural system. Red oak TBI systems had the highest SOC followed by black walnut, Norway spruce and white cedar with values of 93.2, 83.9, 78.1, and 72.2 t C ha&lt;sup&gt;-1&lt;/sup&gt;, respectively. Red oak TBI systems also had the highest mean tree C content, followed by black walnut, Norway spruce and white cedar, with values of 299.7, 285.8, 255.4 and 70.1 kg C tree&lt;sup&gt;-1&lt;/sup&gt;, respectively. Total system level C, which incorporated SOC, tree C content and tree planting densities was 134.8, 126.4, 115.7, 95.6 and 75.6 t C ha&lt;sup&gt;-1&lt;/sup&gt; respectively for spruce, oak, walnut and cedar TBI systems and the agricultural field. TBI systems provide higher C sequestration potentials than conventional agricultural fields, and Norway spruce and red oak should be included into TBI systems in southern Ontario to maximize C sequestration benefits.

Soybean performance under moisture limitation in a temperate tree-based intercropping system

CONTEXTTree-based intercropping (TBI) systems show promise in reducing the vulnerability of field crops to increasing water stress. TBI can generate several above- and belowground interactions between trees and crops. These interactions remain poorly documented, especially in the context of moisture limitation. OBJECTIVEThe objective of this study was to determine the performance of soybean within a TBI system under moisture limitation. We hypothesized that TBI generates both positive (near the alleyway centre) and negative (near the trees) effects on soybean performance and that these effects are accentuated when moisture availability decreases. METHODSA partial rainfall interception treatment (50% of the soil surface) in a soybean crop (stages R1 to R7) was installed for two years (2018 and 2019) in a TBI (50 trees/ha planted in 2012) in southern Quebec. TBI was composed of hybrid poplars (Populus deltoides × P. nigra) and different high-value hardwood species that were planted alternately within rows. A tree root-pruning treatment was also applied to understand belowground effects of tree roots on soybean growth under moisture limitation. Various microclimatic (light availability, wind speed and soil moisture) and soybean performance variables (leaf traits, 100-grain weight and yield) were measured at four distances from the tree row (4, 12 and 20 m, and control). RESULTS AND CONCLUSIONSRainfall exclusion decreased soil moisture and had a negative effect on soybean yield (−14%). The effect of the rain exclusion treatment on soybean performance was similar across all tree row distances and in both root-pruning treatments, which is contrary to our prediction. In 2018, an abnormally dry and warm season, yield near the alley centres was higher than near the tree row and tended to outperform the control. In 2019, a season with normal rainfall and temperature, soybean yield within the alleys was consistent among the different measured distances and did not differ from that in the control. Moderate shading at 4 m (−26% of PAR) was not associated with a change in soybean yield or leaf traits compared to other distances where shading was negligible or absent. Root pruning negatively affected soybean yield in 2018 (−14%) and 2019 (−22%), which is contrary to our prediction. SIGNIFICANCEThis case study adds to our knowledge regarding interactions between crops and trees in widely spaced TBI systems. TBI effects on spatial patterns of crop yield may vary substantially depending upon inter-annual variation in climatic conditions. This study suggests that more facilitative effects would prevail in dryer and warmer years, in contrast to near neutral effects in normal years.

SOIL QUALITY OF AGRICULTURAL LANDS: A STUDY IN LORALAI DISTRICT, BALOCHISTAN, PAKISTAN

Loralai is the district of Balochistan, Pakistan. Climate of this region is arid and farmers rely on rainfall and groundwater irrigation. In this study, seven orchards, seven croplands, two farms under tree-based intercropping were sampled for soil organic matter (SOM) and soil macrofauna. These farms have diverse management history and are of various ages since under agricultural practices. The soil organic matter in upper soil layer (0-10 cm depth) of orchards was 30% higher (18.9 ± 6.3 g kg-1 soil) than croplands (13.2 ± 2.9 g kg-1 soil; P &lt; 0.05). The highest concentration of SOM was found in the soil of diversified tree-based intercropping field (26.07±1.35 g kg-1 soil) with the history of 10 years of conservation agriculture (shallow tillage with organic and inorganic fertilizer input) and crop rotation with no fallow period. The total number of macrofauna and number of species of macrofauna was also found higher in diversified tree-based intercropping system. In general, number of soil fauna was higher in the orchards (5.25 ± 3.3 per site sampled) than croplands (2 ± 0.81 per site sampled). This study demonstrates that diversified agro-ecosystem under conservation agriculture in this arid region enhanced concentration of SOM and number and species of soil macrofauna.

Photosynthesis and Fine Root Growth Dynamics of Soybean in Walnut-Soybean Agroforestry System.

Agroforestry system is regarded as a promising practice in sustainable agricultural management. However, the effects of long-term tree-based intercropping on crop remain poorly understood, especially in the Loess Plateau (China). In this study, the impacts of photosynthetic and respiration rate were determined by the portable photosynthesis system (Li-6400), and the effects of the root growth dynamics of soybean in the walnut-soybean intercropping system were measured by soil auger and WinRHIZO root analysis system, in the Loess Plateau. The results showed that soybean reached the highest net photosynthetic rate during flowering period, with the net photosynthetic rate of intercropped soybean, which was 20.40 μmol·m−2·s−1, significantly higher than that of its monocropped counterpart. Soybean biomass reached the maximum during the pod-bearing period, with intercropped soybean biomass being 25.49 g, significantly higher than that of its monocropped counterpart. The mean diameter and increased density of soybean fine roots reduced along with increased soil depth. Both the diameter (0.43 mm) and increased density (930 cm/dm3) of intercropped soybean fine roots were evidently higher than those of monocropped soybean (0.35 mm, 780 cm/dm3). With increasing cropping years, fine roots of intercropped soybean tended to be mainly distributed in soil at a depth between 0 and 20 cm from the fifth year. Collectively, compared with soybean monoculture, walnut-soybean agroforestry system is more conducive to soybean growth in the Loess Plateau.

Soybean Performance Under Moisture Limitation in a Temperate Tree-Based Intercropping System

Soybean Performance Under Moisture Limitation in a Temperate Tree-Based Intercropping System

Influence of shade intensity on growth, biomass allocation, yield and quality of pineapple in mango-based intercropping system

Fruit tree-based intercropping system is commonly practiced in India; however, optimization of light environment for intercrops is essentially required to enhance their productivity. Influence of three shade intensities were examined on growth, biomass allocation pattern, leaf chlorophyll content, nutrient uptake, fruit yield and quality of pineapple in mango-based intercropping system. Compared to the monoculture pineapple system (LE0), the mean shade intensity under LE1, LE2 and LE3 were 23.8 %, 48.6 % and 73.3 %, respectively, whereas the mean PAR availability was 76.2 %, 51.4 % and 26.7 %, respectively. Significantly higher absolute growth rate (AGR), crop growth rate (CGR) and relative growth rate (RGR) was recorded under medium shade intensity (LE2). Dry matter accumulation was significantly high under LE2 followed by LE3. The biomass accumulation was significantly high in leaf followed by fruit and stem, whereas root system exhibited minimum biomass accumulation. Biomass of leaf and crown decreased with the plant biomass, whereas the biomass of fruit, stem and sucker increased. Contents of Chl a, Chl b and Chl a + b increased with the shade intensity and were found maximum under LE3. A gradual increase in N and P contents were observed in the leaves of pineapple with the reduction in PAR transmittance. However, the K content was relatively high under LE2. Increased fruit yield, fruit weight and fruit/crown ratio were recorded under moderate shade intensity (LE2). Total soluble solids and sugar content marginally decreased with the reduction in light intensity, whereas titratable acidity increased. Sunburn intensity significantly reduced under LE2 and LE3. Path analysis studies indicated that plant biomass was that most important predictor for fruit yield in pineapple. Our findings demonstrate that in eastern tropical region of India pineapple may be cultivated as an intercrop with ∼50 % shade intensity since the performance of crop is significantly affected under monoculture system.

Carbon partitioning in a walnut-maize agroforestry system through arbuscular mycorrhizal fungi

In tree-based intercropping systems, roots of trees and crops are interacting and could influence ecosystem services provided by soil microorganisms. Here, the analysis of diversity of arbuscular mycorrhiza fungi (AMF) associated with roots of walnut and maize reveals differences. Of interest, Funneliformis genus is mainly associated with maize roots, and one OTU related to an uncultured Glomus, might form a common mycorrhizal network linking roots of both plants. In addition, the analysis of 13C of mycelium living in the surrounding environment of roots, suggest that part of the carbon derived from walnut trees could be transferred to maize plants. Our results suggest that in temperate agroforestry ecosystems, AMF could participle in the redistribution of nutrients between connected plants.

The competitive effect of almond trees on light and nutrients absorption, crop growth rate, and the yield in almond–cereal agroforestry systems in semi-arid regions

In recent years, the management of agroforestry systems has been widely focused on reducing the soil erosion and water losses, restoration of environmental balance, increasing the land use efficiency, and elevating economic benefits in different regions. This study was conducted in 2015 to evaluate the interspecific competition in tree-based intercropping systems in a semiarid region of Saman County, Chaharmahal and Bakhtiari Province, Iran. Wheat and barley intercropping with almond trees in comparison with the conventional sole-cropping was investigated in terms of the photosynthetic active radiation (PAR), leaf area index, crop growth rate (CGR), net assimilation rate (NAR), amount of the residual elements in the soil, soil organic carbon, and crop yields at three distances from the trees (0.5 m, 1.5 m, and 2.5 m). According to the results, the PAR intercepted by the crops increased with distances from the tree. The highest intercepted PAR in almond–barley and almond–wheat systems was 1017 and 796 µmol m−2 s−1, respectively, at a distance of 2.5 m from the trees. The shading of the almond tree at 0.5 m from the trunk caused a reduction in the intercepted PAR by about 80%. This trend was repeated for the NAR and CGR, which had the highest values at distance of 2.5 m from the tree. The highest grain yields for wheat and barley (2985 and 2180 kg ha−1, respectively) were obtained by intercropping systems at the distance of 2.5 m from the trees, which were 35% and 39% higher than their respective monocultures. The remaining nutrients in the soil were also affected by the planting systems and their distance from the tree. For example, in barley–almond system, the highest amounts of soil organic carbon (0.89 g kg−1), total nitrogen (0.8 g kg−1), phosphorus (15.5 mg kg−1), and potassium (289 mg kg−1) in soil were observed at a distance of 0.5 m from the almond trees, which were higher than the monoculture by about 55, 63, 48, and 53%, respectively. In general, the amounts of residual nutrients of the soil were greater for the agroforestry system. The reduction of PAR in agroforestry systems was the most important crop limitation, which can be managed by increasing the distance from the trees. According to the data regarding carbon, nitrogen, phosphorus, and potassium residues in the soil of agroforestry system, it could be concluded that soil fertility was not limiting crop performance.

Light availability, weed cover and crop yields in second generation of temperate tree-based intercropping systems

An experimental network representing a new generation of widely spaced tree-based intercropping (TBI) systems, which are more adapted to large-scale annual crops than narrowly spaced ones, was established in southern Quebec. Over two consecutive growing seasons (2016-2017), we determined effects of these TBI systems on percent total light transmittance (PTLT), soil moisture, weed cover and crop yield. We studied six experimental sites that included different annual crops (maize, soybean, wheat, black bean) or forage crops. Age of TBI systems varied between 3 and 22 years, and spacing between tree rows ranged from 25 to 90 m. Variables were measured in control (non-tree) farm plots and in TBI alleys at four distances from the row of trees. Spatial variation in crop yield in TBI alleys was crop-specific. Yield reductions for maize, soybean and black bean were observed at the closest distance to the tree row (½H, where H = tree height). These yield reductions were associated with a decrease in PTLT or an increase in weed cover. Soil moisture changed little with distance from the row of trees and no significant relationship between crop yield and soil moisture was measured, which suggested that competition for water between trees and crops was marginal. Our results indicate that forage crops are less sensitive than annual crops to changes in environmental conditions that were incurred by TBI systems. Overall, the second-generation TBI systems under study exerted neutral net effects on integrated crop yields (i.e., all distances combined), except for black bean in 2016. Second-generation TBI agricultural yields appear to be more promising than those obtained in first-generation TBI systems.

Changes in the Soil Bacterial Community in a Chronosequence of Temperate Walnut-Based Intercropping Systems

Agroforestry (tree-based intercropping) is regarded as a promising practice in sustainable agricultural management. However, the impacts of converting cropland to an agroforestry system on microbial communities remain poorly understood. In this study, we assessed the soil bacterial communities in conventional wheat monoculture systems and a chronosequence (5–14 years) walnut-wheat agroforestry system through the high-throughput sequencing of 16S rRNA genes to investigate the effect of agroforestry age on soil bacterial communities and the correlation between soil properties and bacterial communities in the agroecosystem. Our results demonstrate that establishing and developing walnut tree-based agroforestry increased soil bacterial diversity and changed bacterial community structure. Firmicutes, Proteobacteria, Actinobacteria and Acidobacteria were the dominant soil bacterial phyla and Bacillus was the dominant genus. Crop monoculture systems were characterized by the Bacillus (Firmicutes)-dominated microbial community. The relative abundance of Bacillus decreased with agroforestry age; however, subgroups of Proteobacteria and Actinobacteria increased. Of the selected soil physicochemical properties, soil pH and bulk density were significantly correlated with bacterial alpha diversity, and soil pH and organic carbon were the principal drivers in shaping the soil microbial structure as revealed by redundancy analysis (RDA).

Establishment success of seven hardwoods in a tree-based intercropping system in southern Quebec, Canada

In temperate tree-based intercropping (TBI) systems, good survival and early growth of selected tree species without wood defects is critical, when taking into account both economic considerations and rapidly accruing environmental benefits that are provided by the trees. The establishment success of different tree species that have contrasting growth strategies in Northeastern American TBI systems have not been assessed in a well-documented manner, which is an important influential barrier limiting their adoption by farmers. We analyzed establishment success after five growing seasons of six hardwood species and four hybrid poplar clones in a 50 stems ha−1, tree-based intercropping system. The hardwood species being evaluated were Carya ovata, Juglans nigra, Quercus bicolor, Quercus macrocarpa, Quercus rubra, and Acer saccharum. The hybrid poplar clones being evaluated were four clones of Populus deltoides × P. nigra × P. maximowiczii. We also compared 3-year-old bareroot (165 cm in height) with tree shelter versus 6-year-old root-balled transplants (370 cm in height) without tree shelter for two hardwood species (Quercus rubra and Acer saccharum). Mean survival rate of the six hardwood species originating from 3-year-old transplants was 70% after 5 years. Acer saccharum (33%) and Carya ovata (57%) had the lowest survival rates. Tree height of Quercus bicolor and Quercus macrocarpa was taller than that of Carya ovata, Juglans nigra and Quercus rubra. Tree height of Acer saccharum was intermediate among species. Mean survival rate of hybrid poplar after five growing seasons was 82% and did not differ among the clones. Growth of DN 4813 was lower than that of DN×M 915508, DN 3570 and DN 3585. Tree external defects (forks, frost cracks, trunk inclinations, trunk wind bends, and physical injuries) were observed in 63% of the hardwoods and 55% of the hybrid poplars. Red oak and sugar maple originating from 6-year-old transplants had survival rates of 100%. Over 5 years, height increment of 6-year-old transplants was higher than that of 3-year-old transplants. The 6-year-old transplants of Quercus rubra and Acer saccharum were the most cost-effective stock type. We conclude that tree survival, tree growth and tree external defects in establishment phase of TBI systems may vary considerably across hardwood species, hybrid poplar clones and planting stock type.

Agroforestry systems reduce invasive species richness and diversity in the surroundings of protected areas

The Serra do Brigadeiro State Park (PESB) is one of the largest fragments of Brazilian Atlantic Rainforest, and it is relevant for native species conservation. However, monocultures settled around the Park resulted in extensive open areas that facilitate the establishment of alien species on the PESB perimeter, which may threaten native species conservation therein, since biological invasion is the second main cause of global biodiversity loss. In this region, there are also farmers planting agroforestry systems (AFS), characterized by tree-based intercropping, which are structurally more similar to the Atlantic Rainforest reminiscent fragments present in the region and may limit local occurrence of potentially invasive exotic weeds for several reasons, such as the high levels of shade provided by trees, the groundcover that result from loss of tree leaves and the increased competition for belowground resources. This study aimed to test whether AFS limit exotic species establishment when compared to monoculture systems. Accordingly, three coffee monocultures and three agroforestry coffee plantations around the PESB were studied. In each of the six study areas, 30 plots of 1 m2 were established between the lines of coffee plantation, where all species present were surveyed. In both treatments, rarefaction curves were constructed to evaluate native and exotic richness, and diversity of these two categories was estimated through Simpson index inverse (1/D). All 13 sampled exotic species were present in monocultures, but only three of them occurred in AFS. Besides, alien diversity in monocultures ( $$1/D$$ = 2.173 ± 0.011) was significantly higher than in AFS ( $$1/D$$ = 1.031 ± 0.001). Such changes in alien plant community between land-use show that AFSs limit invasive species establishment. Therefore, when planted around protected areas, AFS may contribute to the control of biological invasions and to biodiversity conservation.

Carbon Sequestration vs Agricultural Yields in Tree-Based Intercropping Systems as Affected by Tree Management

Tree-based intercropping (TBI) may increase carbon (C) sequestration in agroecosystems, but may reduce crop yields. In this study of TBI, we used ecosys, a comprehensive mathematical model of terre...

Tree-based intercropping may reduce, while fertilizer nitrate may increase, soil methane emissions

Tree-based intercropping (TBI) systems have shown some promise in mitigating greenhouse gas emissions, such as by sequestering carbon and decreasing soil nitrous oxide emissions. However, the effects of TBI on soil methane fluxes remain unknown. In a field study, we failed to show differences in soil CH4 production between TBI and conventional monocropping (CM) systems. Within TBI plots, however, we found significantly lower CH4 concentrations near the middle of the alleys than closer to tree rows. Soil CH4 concentrations also decreased with soil depth, even dipping below mean global atmospheric concentrations. Laboratory assays revealed a higher CH4 oxidation potential in soils collected from TBI plots compared with CM plots. These assays also revealed a decrease in CH4 oxidation potential after soils were amended with nitrate. We conclude that TBI could potentially reduce soil CH4 emissions, whereas fertilizer nitrate may increase them.

GREENHOUSE GAS DYNAMICS IN A TREE-BASED INTERCROPPING SYSTEM COMPARED TO AN ORGANIC CONVENTIONAL SYSTEM

Tree-based intercropping (TBI) system has been suggested as an alternative to conventional monocropping (CM) for decreasing overall greenhouse gas (GHG) emissions. However, little is known about th...

Interspecific variation of tree root architecture in a temperate agroforestry system characterized using ground-penetrating radar

Root system architecture regulates belowground access to soil resources. Variation in root architecture is important in agroforestry systems given management objectives to optimize resource acquisition between trees and crops. However, the distributions of live tree roots in agroforestry systems remain understudied due to methodological constraints. In this study, we used ground-penetrating radar (GPR) to describe variation in whole-plant root architecture among tree species at the same agricultural site, with a specific focus on vertical coarse and fine root distributions within the zone of competition with neighbouring crops. Using GPR, we detected coarse roots of five trees species (Quercus rubra L., Juglans nigra L., Populus deltoides × nigra DN177, Picea abies (L.) Karst, and Thuja occidentalis L.) at a tree-based intercropping system in southern Ontario, Canada. A subset of soil profiles were assessed for GPR accuracy. A cumulative root distribution function was used to estimate the rooting depth (D95) of coarse roots. We also measured tree coarse root distributions and fine root density distributions 2 m into the crop rows, in the zone of competition. GPR accurately detected approximately 58 % of coarse roots for each study tree. Coarse root architecture varied among species, with differences in D95 and rooting patterns. Fine root length density distribution also varied among species, but was consistently high at 0.10 and 0.20 m depths regardless of species. Our results suggest differential tree suitability for minimizing belowground competition with crops. Additionally, we illustrate the viability of GPR to characterize vertical profiles of live tree root systems, which is critical for improving our understanding of whole-plant functional traits and belowground plant interactions.

Erratum to: Avian diversity in a temperate tree-based intercropping system from inception to now

Erratum to: Avian diversity in a temperate tree-based intercropping system from inception to now