Higher Root Length Density Research Articles

Brinjal (Solanum melongena) rootstocks improve photosynthetic rate, fruit yield and quality parameters in grafted tomato (Solanum lycopersicum)

The experiment was conducted during winter (rabi) seasons of 2021–22 and 2022–23 at ICAR-Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh to study the improvement in yield and quality parameters in tomato (Solanum lycopersicum L.) cultivar using brinjal (Solanum melongena L.) rootstock. Three improved cultivars of tomatoes i.e. Kashi Aman, Kashi Adarsh and Kashi Chayan were grafted over three brinjal rootstocks, IC-111056, IC- 354557, and Surya. Experimental findings revealed that brinjal rootstocks significantly affected photosynthetic traits, root architectures, fruit yields and quality traits of tomatoes. Maximum photosynthetic rate (23.8 µmol/m2/s) and stomatal conductance (492.74 mmol/m2/s) were recorded in Kashi Chayan grafted over Surya rootstock, whereas chlorophyll fluorescence yields (Fv/Fm) was significantly higher in Kashi Aman self-rooted plants (0.452–0.457). Grafting tomato onto brinjal rootstocks significantly enhanced most of the yield traits, such as fruit number, weight, size and yields. Surya + Kashi Chayan graft combination registered an enhancement in number of fruits and yields by 8.65% and 8.4%, respectively over self-rooted Kashi Chayan. Significantly higher root volumes were noticed in two graft combinations i.e. IC-354557 + Kashi Aman (28.53 cm2) and Surya + Kashi Chayan (27.98 cm2), while 63% and 44.5% higher root length density (RLD) were registered in graft combinations IC-354557 + Kashi Chayan and Surya + Kashi Chayan, respectively over self-rooted Kashi Chayan. Fruit quality such as lycopene and ascorbic acid contents were significantly affected in different rootstocks and scions, whereas fruit acidity was unaffected. From the present study it may be conclude that use of brinjal rootstock Surya significantly improved most of the physiological, yield, root architecture and fruit quality in Kashi Chayan tomato cultivars.

Border row effects improved the spatial distributions of maize and peanut roots in an intercropping system, associated with improved yield.

Border row effects impact the ecosystem functions of intercropping systems, with high direct interactions between neighboring row crops in light, water, and nutrients. However, previous studies have mostly focused on aboveground, whereas the effects of intercropping on the spatial distribution of the root system are poorly understood. Field experiments and planting box experiments were combined to explore the yield, dry matter accumulation, and spatial distribution of root morphological indexes, such as root length density (RLD), root surface area density (RSAD), specific root length (SRL), and root diameter (RD), of maize and peanut and interspecific interactions at different soil depths in an intercropping system. In the field experiments, the yield of intercropped maize significantly increased by 33.45%; however, the yield of intercropped peanut significantly decreased by 13.40%. The land equivalent ratio (LER) of the maize-peanut intercropping system was greater than 1, and the advantage of intercropping was significant. Maize was highly competitive (A = 0.94, CR=1.54), and the yield advantage is mainly attributed to maize. Intercropped maize had higher RLD, RSAD, and SRL than sole maize, and intercropped peanut had lower RLD, RSAD, and SRL than sole peanut. In the interspecific interaction zone, the increase in RLD, RSAD, SRL, and RD of intercropped maize was greater than that of intercropped peanut, and maize showed greater root morphological plasticity than peanut. A random forest model determined that RSAD significantly impacted yield at 15-60 cm, while SRL had a significant impact at 30-60 cm. Structural equation modeling revealed that root morphology indicators had a greater effect on yield at 30-45 cm, with interactions between indicators being more pronounced at this depth. These results show that border-row effects mediate the plasticity of root morphology, which could enhance resource use and increase productivity. Therefore, selecting optimal intercropping species and developing sustainable intercropping production systems is of great significance.

Water Use Strategies and Shoot and Root Traits of High-Yielding Winter Wheat Cultivars under Different Water Supply Conditions

Drought is the most important factor limiting winter wheat yield in the North China Plain (NCP). Choosing high-yielding cultivars is an important measure to minimize the negative effects of drought stress. Field studies were conducted with 10 cultivars in the 2020–2022 seasons under three irrigation treatments (I0, without irrigation; I1, irrigated at jointing stage; I2, irrigated at jointing and anthesis stages) in the NCP to examine the water use strategies and root and shoot traits of high-yielding cultivars under different water supply conditions. The results showed that yield variation among cultivars was 21.2–24.6%, 23.7–25.9% and 11.6–15.3% for the I0, I1 and I2 treatments, respectively. Under water deficit conditions (I0 and I1), high-yielding cultivars reduced water use during vegetative stages and increased soil water use during reproductive stages, especially water use from deeper soil layers. Those cultivars with higher root length density (RLD) in deep soil layers exhibited higher water uptake. Each additional millimeter of water used after anthesis from the 100–200 cm soil layers increased grain yield by 23.6–29.6 kg/ha and 16.4–28.5 kg/ha under I0 and I1, respectively. This water use strategy enhanced dry matter accumulation after anthesis, decreased canopy temperature (CT) and increased relative leaf water contents (RLWC), which ultimately improved grain yield. For winter wheat grown under I2, cultivars that decreased water use after anthesis had higher water productivity (WP). Root length (RL), root weight (RW) and root:shoot ratio were each negatively correlated with grain yield, while above-ground biomass was positively correlated with grain yield. Therefore, higher dry matter accumulation and smaller root systems are two important traits of high-yielding cultivars under sufficient water supply conditions (I2) in the NCP.

Shifts from an extensive to an intensive root nutrient‐acquisition mode with stand development of three Pinus species

Abstract Plant roots employ diverse strategies to acquire soil nutrients, including direct nutrient uptake through absorptive fine roots and root hairs, scavenging nutrients by forming symbioses with mycorrhizal fungi, and mining nutrients by releasing root exudates. However, whether these three strategies are differently coordinated among phylogenetically closely related tree species and how this coordination shifts with stand development remains largely unclear. To fill these knowledge gaps, we measured 13 root morphological, architectural, physiological and mycorrhizal traits tightly related to nutrient‐acquisition of three Pinus species (P. sylvestris var. mongolica, P. densiflora and P. tabuliformis) at young (20‐year‐old) and mature (50‐year‐old) stages planted in nutrient‐impoverished sandy soils, in Northeast China. We found that young trees had thinner absorptive fine roots and a higher specific root length than mature trees across three Pinus species, indicating that roots become morphologically less efficient in ‘do it yourself’ scavenging nutrients during stand development. Moreover, young stands had greater root length density and root area index, and mature stands had faster root‐exudation rates, suggesting that young stands rely more on expanding soil volumes to scavenge nutrients and mature stands depend more on root exudation to ‘mine’ nutrients. The three Pinus species exhibited different nutrient‐acquisition strategies at the mature stage; P. densiflora had higher root length density and root area index, and the other two Pinus species had greater ectomycorrhizal colonization rates. Synthesis. Our findings highlight that phylogenetically closely related tree species may exhibit different nutrient‐acquisition strategies and suggest a shift from an extensive nutrient‐acquisition mode depending more on absorptive fine roots to an intensive nutrient‐acquisition mode relying more on root exudation during stand development.

Different nursery growing systems and growth media improved germination and seedling growth of fever tea (Lippia javanica)

An experiment was set up in a Completely Randomized Design (CRD) to examine the influence of nursery growing methods and growth medium on fever, tea germination, and seedling development. Two nursery growth methods (Conventional-CON and Float tray system FTs) and six different growing medium (pine bark, peat moss, coco peat, vermiculite, sand, and cattle manure) were used. ANOVA was used to compare treatment means, and means were separated using the Least Significant Difference (LSD) at a 5 % significance level. The nursery growing method and growth material exhibited a strong interaction regarding the germination index, germination percentage, seedling height, leaf area, root length, density, and final crop stand. The float tray approach yielded the greatest germination index for peat moss and the lowest for cattle manure. In the float tray method, peat moss and coco peat had the highest germination percentages, whereas cattle manure had the lowest. Under the float tray technique, the tallest seedlings emerged in peat moss and the smallest in coco peat. Peat moss had the most leaf area in the float tray system, whereas coco peat had the least in the conventional technique. Peat moss in the float tray system had the highest root length density while coco peat in the conventional technique had the lowest. Peat moss in the float tray system had the highest final crop stand, whereas seedlings in the conventional and float tray systems had nothing. based on the findings, it is recommended that fever tea seedlings be grown on peat moss using the float tray method

Oil radish, winter rye and crimson clover: root and shoot performance in cover crop mixtures

Abstract Purpose The current knowledge of belowground interactions in intercropping systems is limited due to methodological constraints. The current study aimed to investigate cereal-brassica and cereal-legume-brassica cover crop mixtures regarding mixture effects on root and shoot biomass as well as root traits, vertical root niche differentiation, and complementarity. Methods Sole crops and two- and three-species-mixtures of winter rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and oil radish (Raphanus sativus L. var. oleiformis Pers.) were grown in Germany in a two-year organic field experiment. Root traits were analysed using the monolith method. For discrimination of species root mass Fourier transform infrared (FTIR) spectroscopy was used. Results Oil radish dominated mixtures above- and belowground. Oil radish and its mixtures had highest root length density (RLD) and root mass density (RMD) in subsoil. Rye had highest root biomass and RLD in topsoil. Clover was uncompetitive and had low RLD and RMD. Large but non-significant mixture effects occurred in the shoot, especially for shoot nutrient uptake. Mixture effects were positive for RLD and RMD in subsoil and positive for specific root length (SRL) throughout the whole profile. There was no clear evidence for vertical root niche differentiation and root mass complementarity. Conclusion Oil radish as a mixing partner increased rooting in subsoil. When comparing mixtures and sole crops, morphological changes, i.e. higher SRL in mixtures, were found. Contrary to expectations, changes in root allocation patterns, such as vertical niche differentiation or complementarity of root mass, were not observed.

Water flux and biomass production of native plants at different substrate compactions for landfill phytocaps in Southeast Queensland, Australia

Phytocaps for landfills and degraded sites have multiple benefits provided by the established vegetation, including reducing substrate moisture content and drainage through evapotranspiration. One of the factors affecting plant development measured by biomass production is substrate compaction. However, the relationship between drainage and biomass production related to substrate compaction is largely unknown. In an outdoor pot experiment, four native plant species: Eucalyptus terreticornis, Acacia concurrens, Allocasuarina littoralis, and Themeda triandra, grown in coal overburden at three different relative compactions (RC) levels (64%, 77% and 87% of the maximum compaction) in Southeast Queensland, Australia, over seven months. Evapotranspiration rate was measured by change in pot weight. Drainage for each pot was collected in a container after every irrigation and rainfall. Biomass of plants were harvested for dry shoot and root weight measurement. Additionally, root length density was obtained by a root scanner. Our statistical model predicted that 69.8% RC for maximum weekly ET. Overall, 77% RC treatment resulted in higher total evapotranspiration (1.5%), more significant shoot and root biomass production (17.2% and 11.8%, respectively), higher root length density (33.4%) and lower total drainage (20%) compared to 64% and 87% RC treatments. Native woody species had a higher rate of evapotranspiration and a lower rate of drainage than the native grass. Reduction in drainage was correlated with increase in evapotranspiration rate for all plant species, as the soil moisture content decreases through evapotranspiration. These findings support the notion of maximising evapotranspiration to minimise drainage, a key objective for phytocap design. From biomass production, root biomass closely correlates to a reduction in drainage. Multiple lines of evidence from this study indicate that 77% RC treatment maximises evapotranspiration and plant development and minimises deep drainage for phytocap applications, even though harsh microclimate in this experiment may have constrained plant development and affected the water flux.

Natural Genotypic Variation Underpins Root System Response to Drought Stress in Bambara Groundnut [Vigna subterranea (L.) Verdc.

Bambara groundnut [Vigna subterranea (L.) Verdc.] is grown in rainfed production systems and suffers from periodic drought stress (DS), leading to yield reductions. Natural genotypic variation for root traits is essential for adaptation to water deficit conditions. However, root traits have not been fully utilised as selection criteria to improve DS in bambara groundnut. The present study explored the natural genotypic variation found in single genotypes of bambara groundnut derived from landraces to identify adaptive differences in tap root length (TRL) and root length density (RLD) in response to DS. A diverse core collection of eight bambara groundnut genotypes from various locations (namely, Gresik, LunT, IITA-686, DodR, S19-3, Tiga nicuru, and Ankpa-4, DipC1), were grown for two seasons (2018 and 2019) in polyvinyl chloride (PVC) columns with well-watered (WW) and 30-day DS treatments. Plant samples were collected at 55 days after emergence (DAE) (30 days of DS) and at 105 DAE (30 days of DS plus 50 days of recovery). Under DS, differential TRL among genotypes at 55 DAE was observed, with DodR recording the longest among genotypes with an increase (1% in 2018) in TRL under DS compared to WW, whereas LunT and IITA-686 showed significant (p < 0.001) decrease in TRL (27 and 25%, respectively, in 2018). Average RLD was observed to have the highest reduction under DS in the 90–110 cm layer (42 and 58%, respectively, in 2018 and 2019). Rainy habitat LunT had limited roots in 2018 and recorded the least (0.06 ± 0.013 cm–3) RLD in 2019. However, dry-habitat DodR showed an increase in the RLD (60–90 cm) under DS compared to WW, while dry-habitat S19-3 densely occupied all depths with RLD of 0.16 ± 0.05 and 0.18 ± 0.01 cm cm–3 in the deepest layer in both seasons, respectively. Reduced RLD under DS showed recovery when the plants were re-watered. These plants were additionally observed to have RLD that surpasses the density in WW at all soil depths at 105 DAE. Also, recovery was shown in Tiga nicuru and DodR (0–30 cm) and IITA-686 (90–110 cm) in 2019. Average RLD under DS treatment was associated with substantial grain yield advantage (R2 = 0.27 and R2 = 0.49, respectively) in 2018 and 2019. An increase in TRL allowed DodR to quickly explore water at a deeper soil depth in response to gradually declining soil water availability. High RLD in genotypes such as DodR, DipC1 and S19-3 also offered adaptive advantage over other genotypes under DS. Variation in intrinsic RLD in deeper soil depths in the studied genotypes determines root foraging capacity when facing DS. This suggests that different agroecological environments to which bambara groundnut is subjected in its natural habitat have promoted a phenotypic differentiation in root systems to adapt to ecotypic conditions, which may help offset the impact of DS. The natural genotypic variation exhibited, especially by DodR, could be exploited to identify potential quantitative trait loci (QTLs) that control deep rooting and root length density.

Spatial distribution and dynamics of cotton fine root under film-mulched drip irrigation

Fine roots distribution and dynamics (production, mortality, and longevity) significantly impact the crop soil ecosystems. However, the spatial distribution and dynamics of cotton (Gossypium hirsutum L.) fine roots under film-mulched drip irrigation are poorly understood. The present study aims to characterize these distributions and dynamics measured using a minirhizotron technique and the influence of soil conditions. The non-uniform distribution of soil moisture and salinity may lead to the differences of root length density (RLD) distribution. A clear decreased trend for the average RLD was observed in the shallow soil layer due to high localized salinity accumulated after brackish water irrigation. There existed a clear high soil moisture content strip at depth which may lead to a high RLD peak in the 95–100 cm soil layer. Average live root production was characterized by a very high rate during the initial growth stage followed by a decline after budding, which in turn was followed by a slight increase during boll opening. The average number of new roots was highest during the initial growth stages, decreasing after the budding stage. Thinner roots in the deep soil had shorter lifespans than those in shallow soil. Our study indicated that the minirhizotron technique can be used reliably as an in situ, non-destructive method for estimating cotton fine roots distribution and dynamics under film-mulched drip irrigation. To evaluate cotton fine root distribution and dynamics under film-mulched drip irrigation more accurately, a cotton root system architecture model could be parameterized in space and time based on the minirhizotron observations.

Critical phosphorus requirements of Trifolium species: The importance of root morphology and root acclimation in response to phosphorus stress.

Differences in root morphology and acclimation to low-phosphorus (P) soil were examined among eight legume species from the Trifolium Section Tricocephalum to understand how these root attributes determine P acquisition. Ornithopus sativus was included as a highly P-efficient benchmark species. Plants were grown as microswards in pots with five rates of P supplied in a topsoil layer to mimic uneven P distribution within a field soil profile. Topsoil and subsoil roots were harvested separately to enable measurement of the nutrient-foraging responses. Critical P requirement (lowest P supply for maximum yield) varied over a threefold range, reflecting differences in root morphology and acclimation of nutrient-foraging roots to P stress. Among the species, there was a 3.2-fold range in root length density, a 1.7-fold range in specific root length, and a 2.1-fold range in root hair length. O. sativus had the lowest critical P requirement, displayed a high root length density, the highest specific root length, and the longest root hairs. Acquisition of P from P-deficient soil was facilitated by development of a large root hair cylinder (i.e. a large root-soil interface). This, in turn, was determined by the intrinsic root morphology attributes of each genotype, and the plasticity of its root morphology response to internal P stress. Root acclimation in low-P soil by all species was mostly associated with preferential allocation of mass to nutrient-foraging roots. Only O. sativus and four of the Trifolium species adjusted specific root length beneficially, and only O. sativus increased its root hair length in low-P soil.

Rotation crop root performance and its effect on soil hydraulic properties in a clayey Utisol

Poor soil hydraulic properties (SPH) limit the productivity of clayey Utisol (red soil) under a humid subtropical climate in southern China. The roots performance of rotation crops was compared, and the effects on SPH were investigated in the field. Five treatments (two cultivars of oilseed rape, one-year-old lucerne, and one- and five-year-old vetiver) were employed as pre-crops before summer maize, and their root performances were examined in spring. The soil-water characteristic curve (SWCC) and soil porosity were measured with soil cores, saturated hydraulic conductivity (Ks), and near-saturated hydraulic conductivity with a tension infiltrometer in situ. The two rape cultivars had the thinnest root diameter at an average of 0.45−0.50 mm and the shallowest distribution at a depth of 40 cm, while two vetivers had the thickest mean root diameter at 0.79 mm and the deepest distribution >80 cm. Taproot crops of rape and lucerne did not show stronger rooting ability than fibrous root crops of vetivers. All crops increased soil total and aeration porosity, but no bio-pores larger than 2 mm were formed. Rapes were beneficial for increasing soil aeration porosity (diameter >30 μm), while vetivers increased active capillary porosity (30−0.2 μm). The SHP, namely, SWCC and Ks, was improved by all crops, with the best effects in the five-year old vetiver due to its higher root length density (RLD) and the balanced distribution between diameter classes. Ks was significantly correlated with RLD (p < 0.001) but insignificantly correlated with root diameter (p = 0.9929). The SHP was improved mainly by RLD and influenced by root diameter distribution, suggesting that fine roots played a key role in forming aeration and active capillary pores.

Digging roots is easier with AI.

The scale of root quantification in research is often limited by the time required for sampling, measurement, and processing samples. Recent developments in convolutional neural networks (CNNs) have made faster and more accurate plant image analysis possible, which may significantly reduce the time required for root measurement, but challenges remain in making these methods accessible to researchers without an in-depth knowledge of machine learning. We analyzed root images acquired from three destructive root samplings using the RootPainter CNN software that features an interface for corrective annotation for easier use. Root scans with and without non-root debris were used to test if training a model (i.e. learning from labeled examples) can effectively exclude the debris by comparing the end results with measurements from clean images. Root images acquired from soil profile walls and the cross-section of soil cores were also used for training, and the derived measurements were compared with manual measurements. After 200 min of training on each dataset, significant relationships between manual measurements and RootPainter-derived data were noted for monolith (R2=0.99), profile wall (R2=0.76), and core-break (R2=0.57). The rooting density derived from images with debris was not significantly different from that derived from clean images after processing with RootPainter. Rooting density was also successfully calculated from both profile wall and soil core images, and in each case the gradient of root density with depth was not significantly different from manual counts. Differences in root-length density (RLD) between crops with contrasting root systems were captured using automatic segmentation at soil profiles with high RLD (1-5 cm cm-3) as well with low RLD (0.1-0.3 cm cm-3). Our results demonstrate that the proposed approach using CNN can lead to substantial reductions in root sample processing workloads, increasing the potential scale of future root investigations.

Comparison of early season crop types for wheat production and nitrogen use efficiency in the Jianghan Plain in China.

The rice-wheat (RW) cropping system is one of the most prevalent double-cropping systems used to farm the Jianghan Plain in China. However, it can lead to low wheat yields and reduced nitrogen use efficiency compared with dryland wheat (DW). We evaluated wheat yield and nitrogen use efficiency for two rotations (summer rice-winter wheat and summer soybean-winter wheat) from 2017 to 2019 and applied the results to improve nitrogen management for planting wheat after rice in the Jianghan Plain. Field experiments were conducted over two years with two nitrogen treatments: traditional nitrogen management (M1: 90 kg N ha−1 was applied at sowing and jointing, respectively ) and optimized nitrogen management (M2: 60 kg N ha−1 was applied at sowing, wintering and jointing, respectively). The highest total wheat production was achieved under M2 for both cropping systems and the two-year average yield was 6,128 kg ha−1 in DW and 6,166 kg ha−1 in RW. The spike number in DW was 15% higher than RW in M1 and 13% higher in M2, but the kernel per spike and 1,000-grain weight was lower than RW. The nitrogen accumulation of DW was 24% higher than RW in M1 and 33% in M2. Compared with RW, DW had higher NO3− content in the soil surface layer (0–20 cm) and a higher root length density (RLD) in the deeper layer (40–60 cm), which may account for the higher N uptake in DW. Our results show that the grain yield of RW was comparable to that of DW by optimum nitrogen management. The rice-wheat cropping system combined with optimum nitrogen management may be of economic and agronomic benefit to the wheatbelt in the Jianghan Plain in China.

Conservation tillage and preceding rainy-season crops on root: shoot characteristics, productivity, profitability and nutrient uptake of succeeding mustard under semi-arid rainfed ecosystem

Conservation tillage practices are poplar, environmental friendly and economically feasible approaches to increase the productivity and resource-use efficiency of arid and semi-arid rainfed ecosystems. Rainfed field experiments were accomplished at IARI, Pusa, New Delhi in 2010-11 and 2011-12 to evaluate root: shoot growth, productivity, profitability and nutrient uptake in mustard under the various conservation tillage practices with preceding rainy- season crops; pearlmillet, clusterbean and greengram; and organic mulches, viz. no residues, crop residues and Leucaena twigs applied to both rainy- season crops and mustard grown with common recommended package of practices. Higher root length density (RLD), root surface area (RSA), root volume density (RVD), average root diameter (RD), crop growth rate (CGR), relative growth rate (RGR) and net assimilation rate (NAR) were recorded under clusterbean–mustard and greengram–mustard systems over the pearlmillet- mustard system. Interaction between crop residues and preceding rainy-season crops on growth parameters exerted significant variations, while yield attributes showed the mixed responses. Mustard seed yield was significantly higher (+51%) in 2010-11 (1.80 t ha-1) than that of 2011-12 (1.19 t ha-1). Economic analysis exhibited the highest returns and net returns/ Rs invested after clusterbean with Leucaena twigs mulching. The nutrient uptake followed the same trend as that of seed and stalk yield. It was concluded that growing mustard after clusterbean with Leucaena twigs mulching was high-yielding and profitable cropping system under conservation tilled semi-arid rainfed ecosystem.

Improving Water Use Efficiency by Optimizing the Root Distribution Patterns under Varying Drip Emitter Density and Drought Stress for Cherry Tomato

The spatial distribution of root systems in the soil has major impacts on soil water and nutrient uptake and ultimately crop yield. This research aimed to optimize the root distribution patterns, growth, and yield of cherry tomato by using a number of emitters per plant. A randomized complete block design technique was adopted by selecting eight treatments with two irrigation regimes and four levels of emitters under greenhouse conditions. The experiment results showed that the root distribution extended over the entire pot horizontally and shifted vertically upwards with increased emitter density. The deficit irrigation resulted in reduced horizontal root extension and shifted the root concentrations deeper. Notably, tomato plants with two emitters per plant and deficit irrigation treatment showed an optimal root distribution compared to the other treatments, showing wider and deeper dispersion measurements and higher root length density and root weight density through the soil with the highest benefit–cost ratio (1.3 and 1.1 cm cm−3, 89.8 and 77.7 µg cm−3, and 4.20 and 4.24 during spring–summer and fall-winter cropping seasons, respectively). The increases in yield and water use efficiency (due to increased yield) were 19% and 18.8%, respectively, for spring–summer cropping season and 11.5% and 11.8%, respectively, for fall–winter cropping season, with two emitters per plant over a single emitter. The decrease in yield was 5.3% and 4%, and increase in water use efficiency (due to deficit irrigation) was 26.2% and 27.9% for spring-summer and fall-winter cropping seasons, respectively, by deficit irrigation over full irrigation. Moreover, it was observed that two, three, and four emitters per plant had no significant effects on yield and water use efficiency. Thus, it was concluded that two emitters per plant with deficit irrigation is optimum under greenhouse conditions for the cultivation of potted cherry tomatoes, considering the root morphology, root distribution, dry matter production, yield, water use efficiency, and economic analysis.

Manipulating plant community composition to steer efficient N‐cycling in intensively managed grasslands

Abstract Minimizing nitrogen (N) losses and increasing plant N uptake in agroecosystems is a major global challenge. Ecological concepts from (semi)natural grasslands suggest that manipulating plant community composition using plant species with different traits may represent a promising opportunity to face this challenge. Here, we translate these trait‐based concepts to agricultural systems in a field experiment, aiming to reveal the main determinants of how plant community composition regulates N‐cycling in intensively managed grasslands. We focused on key N pools (plant N from soil and from biological N‐fixation, soil mineral N and N2O emissions) as well as on biological drivers of N‐cycling in soil (abundance of N‐cycling microbial communities, earthworm populations and arbuscular mycorrhizal fungi), using three common grass and one legume species in monoculture, two‐ and four‐species mixtures. We hypothesized that: (a) plant species mixtures increase plant N uptake, reduce soil mineral N concentrations and N2O emissions and promote the abundance of biological N‐cyclers; (b) legume presence stimulates N pools, fluxes and biological N‐cycling activity, (c) but in combination with a grass with acquisitive traits, more N is retained in the plant community, while N2O emissions are reduced. We found that mixtures increased plant N and lowered the soil mineral N pool compared to monocultures. However, plant species identity played an overarching role: Legume presence increased N2O emissions, plant N pools, soil mineral N and the abundance of N‐cycling microbes and earthworms. Combining the legume with a grass with low leaf dry matter content and high root length density (and with high root biomass) reduced the higher soil mineral N and N2O emissions induced by the legume, while harnessing positive effects on plant N pools and biological N‐fixation. Synthesis and applications. Our results show the potential of plant community composition to steer N‐cycling in fertilized agroecosystems, paving the way for a more biologically based agriculture. Legumes will play a crucial role, but selecting an optimum companion species is key for the sustainability of the agroecosystem.

Vertical Root Distribution of Different Cover Crops Determined with the Profile Wall Method

Many benefits of cover crops such as prevention of nitrate leaching, erosion reduction, soil organic carbon enhancement and improvement of soil structure are associated with roots. However, including root characteristics as a criterion for cover crop selection requires more knowledge on their root growth dynamics. Seven cover crop species (crimson clover, winter rye, bristle oats, blue lupin, oil radish, winter turnip rape and phacelia) were grown in a two-year organically managed field experiment in Germany to screen them for root intensity and vertical root distribution. Root length density (RLD) and proportion of root length in large-sized biopores were determined before and after winter with the profile wall method. RLD and cumulative root length were analysed using a three-parameter logistic function, and a logistic dose-response function, respectively. Fibrous rooted winter rye and crimson clover showed high RLD in topsoil and had a shallow cumulative root distribution. Their RLD increased further during winter in topsoil and subsoil. The crops with the highest RLD in the subsoil were taprooted oil radish, winter turnip rape and phacelia. Bristle oat had intermediate features. Blue lupin had low RLD in topsoil and subsoil. Phacelia, oil radish, winter turnip rape and bristle oat showed the highest share of root length in biopores. These complementary root characteristics suggest that combining cover crops of different root types in intercropping may be used to enhance overall RLD for maximizing cover crop benefits.

Interactive Effects of Nitrogen and Drip Irrigation Rates on Root Development of Corn (Zea Mays L.) and Residual Soil Moisture

Deficiencies in water and nitrogen (N) can lead to poor crop growth and production. This study was carried out during 2012–2014 to determine (1) the effect of drip irrigation regimes and N fertilizer rates on root length density (RLD) of corn (Zea mays L. cv. Single cross 704) and soil moisture dynamics and (2) the relationship between root development and water availability. The experiment was arranged into a split-plot design with three irrigation regimes as the main factor (I1 = 60, I2 = 80, and I3 = 100% evapotranspiration [ETc]) and five levels of N fertilizer (N1 = 0, N2 = 50, N3 = 100, N4 = 150 and N5 = 200 kg/ha) as the subfactor. The combination I1N4 produced the highest grain yield and yield components while I3N5 gave the lowest performance. The highest RLD was recorded at full irrigation water requirement and it increased with increasing N rate, but not in a linear trend, as higher N rates showed less effect. Nitrogen application under drip irrigation increased the RLD in soil depending on irrigation level. Soil moisture was optimized at full irrigation water requirement and 150 kg/ha N.

Root architecture, rooting profiles and physiological responses of potential slope plants grown on acidic soil.

Globally, there has been an increase in the frequency of landslides which is the result of slope failures. The combination of high intensity rainfall and high temperature resulted in the formation of acidic soil which is detrimental to the healthy growth of plants. Proper plant coverage on slopes is a prerequisite to mitigate and rehabilitate the soil. However, not all plant species are able to grow in marginal land. Thus, this study was undertaken to find a suitable slope plant species. We aimed to evaluate the effect of different soil pH on root profiles and growth of three different potential slope plant species namely, Melastoma malabathricum, Hibiscus rosa-sinensis and Syzygium campanulatum. M. malabathricum showed the highest tolerance to acidic soil as it recorded the highest plant height and photosynthetic rate. The root systems of M. malabathricum, H. rosa-sinensis and S. campanulatum were identified as M, VH- and R-types, respectively. The study proposed M. malabathricum which possessed dense and shallow roots to be planted at the toe or top of the slope while H. rosa-sinensis and S. campanulatum to be planted in the middle of a slope. S. campanulatum consistently recorded high root length and root length density across all three types of soil pH while M. malabathricum showed progressive increase in length as the soil pH increased. The root average diameter and root volume of M. malabathricum outperformed the other two plant species irrespective of soil pH. In terms of biomass, M. malabathricum exhibited the highest root and shoot dry weights followed by S. campanulatum. Thus, we propose M. malabathricum to be planted on slopes as a form of soil rehabilitation. The plant species displayed denser rooting, hence a stronger root anchorage that can hold the soil particles together which will be beneficial for slope stabilization.

Root and crop responses of sweet pepper (Capsicum annuum) to increasing N fertilization

Rooting is the mechanism by which roots explore soil resources to nourish and anchor the plant to the ground. In vegetable crops, nitrogen (N) application exceeds crop demand due to over fertilization, thereby contributing to N losses through nitrate (NO3−) leaching. To improve N fertilization, knowledge of the response of rooting behaviour and root dynamics to N fertilization will be very useful. In this study, the effect of rates of N application on rooting were assessed in two sweet pepper (Capsicum annuum) crops grown in an artificially layered soil, with sand mulch, in Almería (south-eastern Spain). The treatments were very deficient, conventional, and very excessive in terms of N application. Yield, crop N absorption and dry matter of the shoot part were determined. Statistically significant differences were found in shoot dry matter between the very deficient N, compared to conventional and very excessive N. Root length density decreased with increasing application of N, with significantly higher density in the very deficient N application. In relation to depth, root length density in the very deficient N was nearly double (in the 2016 crop) and triple (in the 2017 crop) than in conventional N in the sand mulch layer (0–0.10 m depth). In contrast, root length density in the very deficient N treatment was in general lower than in conventional and very excessive N application in the 0.10–0.20 m layer. In the deeper layers, 0.20–0.30 and 0.30–0.40 m, no effects of N treatments on root length density were found. In relative terms, plants subjected to very deficient N treatment allocated relatively more roots in the sand mulch layer and less roots in the 0.10–0.20 m layer than when subjected to conventional and very excessive N. Root length density was negatively correlated with shoot dry matter, crop N absorption, yield and residual soil mineral N at the end of the crops. Overall, results of the present work suggest that conventional and very excessive N application maximized the development of the shoot part and crop yield and diminished root length density, particularly in the sand mulch layer (0–0.10 m depth). A higher root length density was not sufficient under very deficient N in terms of matching dry matter and yield of the conventional N treatment.