Total Root Production Research Articles

Age‐related changes in root dynamics of a novel perennial grain crop

AbstractBackgroundStanding root biomass stocks are larger in the perennial grain intermediate wheatgrass (IWG; Thinopyrum intermedium [Host] Barkworth and Dewey) than annual spring wheat (Triticum aestivum L.). However, previous studies have not separated root growth from root decomposition, which presents a significant gap in our understanding of how roots can contribute to soil organic carbon (C) accrual or other soil properties through time.MethodsWe used paired sequential coring and root ingrowth cores to measure standing root stock, new root production, root decomposition, and decomposed root C and N from 0 to 15 cm soil depth of 1‐year‐old IWG (IWG‐1), 2‐year‐old IWG (IWG‐2), and annual spring wheat.ResultsStanding root stock was 3.2–6.5 and 6.3–9.9 times higher in IWG‐1 and IWG‐2 than wheat. Total root production was 1.7 times greater in IWG‐1 than IWG‐2. Conversely, root decomposition almost doubled from 1.39 to 2.43 kg m−3 between IWG‐1 and IWG‐2.ConclusionsIn IWG, decreased root production and increased root decomposition with stand age suggest a change in growth strategy that could reduce the contribution of root‐derived C to stabilized soil C pools as IWG stands age.

Fine root dynamics of Kandelia obovata, Rhizophora stylosa and Bruguiera gymnorrhiza in a mangrove environment in Okinawa, Japan

The present study investigates the fine root dynamics including comparison of fine root production, mortality and decomposition of Kandelia obovata (S., L.) Yong, Rhizophora stylosa Griff. and Bruguiera gymnorrhiza (L.) Lamk. in the Manko Wetland of Okinawa, Japan considering the importance of fine root to the ecosystem carbon dynamics. Our objective was to investigate seasonal dynamics of fine root of the three species and explore whether there is variation among species using sequential core and ingrowth core methods. The root systems were separated into living and dead mass fractions and these were subsequently separated as very fine roots (<0.5 mm) and fine roots (0.5—2 mm). Total fine root production of K. obovata, R. stylosa and B. gymnorrhiza ranged from 4.7 to 7.1 Mg ha −1 y−1, 1.7 to 3.6 Mg ha −1 y−1 and 2.9 to 4.9 Mg ha −1 y−1, respectively whereas mortality ranged 2.9 to 5.9 Mg ha −1 y−1, 0.6 to 2.3 Mg ha −1 y−1 and 0.8 to 3 Mg ha −1 y−1. The mean fine root turnover of K. obovata, R. stylosa and B. gymnorrhiza were estimated as 3.42, 2.78 and 3.37 y−1 having a longevity of 3.46, 4.32 and 3.56 months, respectively. The amount of decomposition through sequential core and ingrowth core methods for K. obovata, was estimated at 47 and 28 g m−2y−1, respectively, whereas for R. stylosa and B. gymnorrhiza these were 6 and 11 g m−2y−1, and 15 and 19 g m−2y−1, respectively. Significant variation of soil salinity, soil N, soil pH among three species plots was observed although the result was insignificant in different seasons. Using ingrowth core method, we observed significant correlations of fine root production with soil salinity and soil pH, but the results were insignificant with sequential core data. Finally, the significant effect of soil pH was found in the regression model as the predictor of fine root production. Although the seasonal pattern was absent in fine root production, the seasonal change in the biomass and necromass was obvious. The high amount of fine root necromass available can be a great source of organic matter in the forest for carbon and nutrient cycling.

PERFORMANCE OF EXPERIMENTAL ORANGE-FLESHED SWEET POTATO GENOTYPES IN THE WESTERN REGION OF SÃO PAULO

The orange-fleshed sweet potato has interesting nutritional characteristics, as it has a high concentration of β-carotene, which is a precursor of vitamin A. Vitamin A deficiency is a public health problem and can be avoided by adequate intake of β-carotene-rich foods, like the orange-fleshed sweet potato (OFSP). However, few OFSP genotypes are available to growers. The objective of this study was to evaluate the agronomic performance of OFSP experimental genotypes under the edaphoclimatic conditions of Western São Paulo. The experiment was carried out in the municipality of Álvares Machado-SP in a sweet potato production area on a commercial scale. Planting was carried out in October 2021 using a randomized block design with four replications. Five experimental genotypes of OFSP were evaluated, namely: F-09, F-34, U2-05, U2-19 and C-14. The cultivar Beauregard was adopted as control. At 139 days after planting, the tuberous roots were harvested and the following were assessed: total tuberous root production in Kg ha-1; number of commercial tuberous roots in roots ha-1, production of commercial tuberous roots in Kg ha-1; average mass of commercial tuberous roots in g; dry mass percentage of commercial tuberous roots; length of roots in cm, diameter of roots in cm and soluble solids, in °Brix, appearance of roots using a scale of grades, and resistance to damage caused by insect pests. The commercial yield of the evaluated genotypes ranged from 38,27 t ha-1 (Beauregard) to 89,25 t ha-1 (F-34). The experimental genotypes present tuberous root quality similar to the commercial control 'Beauregard'. Genotypes F-34 and C-14 have flesh color similar to 'Beauregard', and genotype F-09 has dark orange flesh, a class above the control. All evaluated genotypes can potentially contribute to the increase in yield in Western São Paulo.

Pisum sativum has no competitive responses to neighbors: A case study in (non)reproducible plant biology.

Plant–plant competition is ubiquitous in nature. However, studying below ground behavior of roots has always posed certain difficulties. Pea ( Pisum sativum L.) has become a common study species for questions about how plant roots respond to neighboring plant roots and barriers in soil. However, published results point in several different directions. This has sometimes been interpreted as pea having sophisticated context dependent responses that can change in complex ways depending on its surroundings, but it could also just point to small statistical power resulting in type I or II statistical errors. To explore this further, here, we combine the result of five new experiments with published results to examine 18 unique experiments from 10 different studies and 6 cultivars of pea for a total of 254 replicate plants. We used a Bayesian hierarchical meta‐analysis approach to estimating the likely effect size from the available data, as well as quantify heterogeneity among different experiments, studies and cultivars. The posterior distributions show that, at the coarsest possible scale of total root production, it is unlikely that P. sativum root growth is influenced by either neighbors or pot volume that varies primarily by depth. We find no evidence of publication bias and conclude that this is simply due to statistical sampling error and the scientific method combined with frequentist statistics operating as intended. We suggest that further work on pea should consider repeating experiments that reported finer scale root plasticity at the rhizosphere scale or consider exploring different pot geometries such as volume that varies by depth or width. We also suggest that more diversity in study species are needed to better understand the neighbor‐volume response.

Estimation of genetic parameters and selection gains for sweet potato using Bayesian inference with a priori information

The selection of superior sweet potato genotypes using Bayesian inference is an important strategy for genetic improvement. Sweet potatoes are of social and economic importance, being the material for ethanol production. The estimation of variance components and genetic parameters using Bayesian inference is more accurate than that using the frequently used statistical methodologies. This is because the former allows for using a priori knowledge from previous research. Therefore, the present study estimated genetic parameters and selection gains, predicted genetic values, and selected sweet potato genotypes using a Bayesian approach with a priori information. Root shape, soil insect resistance, and root and shoot productivity of 24 sweet potato genotypes were measured. Heritability, genotypic variation coefficient, residual variation coefficient, relative variation index, and selection gains direct, indirect and simultaneous were estimated, and the data were analyzed using Bayesian inference. Data from 11 experiments were used to obtain a priori information. Bayesian inference was a useful tool for decision-making, and significant genetic gains could be achieved with the selection of the evaluated genotypes. Root shape, soil insect resistance, commercial root productivity, and total root productivity showed higher heritability values. Clones UFVJM06, UFVJM40, UFVJM54, UFVJM09, and CAMBRAIA can be used as parents in future breeding programs.

Fine Root Production and Soil Available Nutrients in Rubber Monoculture versus Rubber–Flemingia macrophylla Agroforestry

In the present study, we examined fine root production and soil available nutrients (N, P and K) across different soil depths in rubber monoculture and rubber–Flemingia macrophylla agroforestry of different stand ages. We used the ingrowth cores method and sampled 360 soil cores over four growth intervals, representing one year of growth for the present study. The results showed that root production and macronutrient concentrations generally decreased with increasing soil depth. Total fine root production was comparatively high in the youngest stand age (12 years) rubber monoculture; a similar trend was observed for the soil available P and K, but available N was greater in older than younger stand ages. Root growth and soil available P and K were all lower in the agroforestry system than the monoculture. Significant differences in fine root production with stand ages, management system and seasons suggest that fine root responses to the soil available nutrients are vital to understanding the precise response of above- and belowground biomass to environmental changes.

Estimation of total fine root production using continuous inflow methods in tropical mangrove forest on Pohnpei Island, Micronesia: Fine root necromass accumulation is a substantial contributor to blue carbon stocks

AbstractFine root decomposition, mortality, and production are fundamental components of belowground carbon dynamics in mangrove ecosystems. Mangroves are highly productive ecosystems with huge carbon stocks; however, information on the dynamics of submerged fine roots in mangrove soils is limited. To estimate fine root production in several sites of mangrove communities on Pohnpei Island, Micronesia, we estimated continuous inflows using a simple mass balance model to combine ingrowth core and litterbag experimental results. According to our findings, previously reported mangrove fine root production values were severely underestimated because the fine root decomposition process was disregarded during the experimental period. We estimated that annual fine root production up to 0.3 m in depth ranged from 13.8 (Bruguiera gymnorrhiza in a landward plot) to 56.3 Mg ha−1 year−1 (B. gymnorrhiza in a seaward plot). However, comparing the fine root production with respect to the unit of stem cross‐section area increase in the sample tree, the fine root production of Rhizophora spp. was greater than that of other species. The annual fine root mortality and decomposition to annual fine root production was 70%–105% and 11%–52% of annual production, respectively. The annual fine root production estimated here was much higher than that previously reported. These findings begin to quantify the contribution and importance of highly productive mangrove fine roots for carbon sequestration in blue carbon ecosystems. Moreover, this study provides new insights into the organic carbon dynamics in mangrove soils with mangrove vegetation succession.

Development of wheat bread added with insoluble dietary fiber from ginseng residue and effects on physiochemical properties, in vitro adsorption capacities and starch digestibility

In general, fresh ginseng is largely produced globally by four countries (South Korea, China, Canada, and the USA) accounting for 99% of total world ginseng root production (79,769 tons). This study was aimed at preparation of wheat bread supplemented with ginseng insoluble dietary fiber (GSI) and effects of GSI supplementation on physicochemical properties, bioactive compounds, antioxidant activities, absorption capacities, starch digestibility and sensory attributes were evaluated. Overall, GSI addition up to 4% significantly (p < 0.05) improved nutritional components, polyphenolic compounds, antioxidant activities, and sensory scores of supplemented bread samples, whereas addition levels above 4% led to development of undesirable texture and sensory properties. Concentration-dependent increases in NO2− ion, cholesterol and bile acid adsorption capacities were evident with corresponding rises in GSI addition levels from 2 to 8%. GSI-addition showed significant concentration-dependent decreases in glucose release response during various in vitro starch digestion intervals. Based on the sensory properties, wheat bread with GSI (4%) showed excellent overall acceptability. GSI-supplemented bread up to 4% could be utilized as a convenience food and hence may serve as a resource of important nutritional bioactive compounds with improved functional properties.

High tolerance to simulated root herbivory in hydroponically grown cuttings of Salix phylicifolia

The shortage of information regarding the effects of root damage on forest plants, especially trees and shrubs, is the most critical gap in our knowledge of belowground insect herbivory. This study examines how the tea-leaved willow, Salix phylicifolia, responds to simulated root herbivory and how nutrient availability affects these responses. Hydroponically grown cuttings were used to precisely apply the desired levels of root damage. Root: shoot ratios increased proportionally to the intensity of root damage, whereas specific leaf area, leaf water content and chlorophyll fluorescence were not affected. The removal of 2–64% of roots once in early summer and the removal of 25% of roots three times during the summer did not change biomass production by cuttings. The repeated removal of 50 and 75% of roots decreased shoot biomass and, to a lesser extent, total root production. The tolerance of tea-leaved willow to root damage was greater in low nutrient treatment than in high nutrient treatment, thus supporting the Growth Rate Model. According to this model, in low resource conditions plants do not attain their maximum growth rate and therefore have a higher capacity for regrowth after damage. We conclude that, in the absence of water limitations, tea-leaved willow shows high tolerance to root losses and is unlikely to be affected by realistic levels of root herbivory.

Remarkable Similarity in Timing of Absorptive Fine-Root Production Across 11 Diverse Temperate Tree Species in a Common Garden.

Long-term minirhizotron observations of absorptive fine roots provide insights into seasonal patterns of belowground root production and carbon dynamics. Our objective was to compare root dynamics over time across mature individuals of 11 temperate trees species: five evergreen and six deciduous. We analyzed the timing and growth on 1st-and 2nd-order roots in minirhizotron images down to a vertical depth of 35 cm, as well as monthly and total annual length production. Production patterns were related to total annual precipitation of the actual and previous year of root production over 6 years. The main or largest peak of annual fine-root production occurred between June and September for almost all species and years. In most years, when peaks occurred, the timing of peak root production was synchronized across all species. A linear mixed model revealed significant differences in monthly fine-root length production across species in certain years (species x year, P < 0.0001), which was strongly influenced by three tree species. Total annual root production was much higher in 2000–2002, when there was above-average rainfall in the previous year, compared with production in 2005–2007, which followed years of lower-than-average rainfall (2003–2006). Compared to the wetter period all species experienced a decline of at least 75% in annual production in the drier years. Total annual root length production was more strongly associated with previous year’s (P < 0.001) compared with the actual year’s precipitation (P = 0.003). Remarkably similar timing of monthly absorptive fine-root growth can occur across multiple species of diverse phylogeny and leaf habit in a given year, suggesting a strong influence of extrinsic factors on absorptive fine-root growth. The influence of previous year precipitation on annual absorptive fine-root growth underscores the importance of legacy effects in biological responses and suggests that a growth response of temperate trees to extreme precipitation or drought events can be exacerbated across years.

Studies on effect of rootstocks on root distribution pattern of cashew

The present investigation on the root distribution pattern of cashew rootstocks was carried out at ICAR-Directorate of Cashew Research (DCR), Experimental Station, Santhigodu, Karnataka. The study aimed to understand the root distribution of two dwarfing rootstocks (NRC 492, Taliparamba- 1) and one vigorous rootstock (Vengurla-4) of eight-years-oldcashew tree, as determined by the root excavation method. The root samples were collected vertically from different depths (0-200 cm) and laterally at different distances (0-300 cm) from the tree trunk. Results indicated that the root distribution pattern showed significant genotypic variation. Regarding the vertical distribution of roots, 95 percent of the roots were distributed in 0-100 cm horizons, while very few roots were in the 100-200 cm horizons. In the lateral distribution, 97 percent of root density was in the 0-200 cm area from the tree trunk. Vengurla-4 (vigorous rootstock) had a higher root length, root volume and two-fold increases in total root production compared to dwarf rootstocks. PCA study revealed that the selection of rootstocks based on tree height, TCSA, canopy spread, lateral and vertical distribution of roots represent the main morphological indices for evaluating the effect of cashew rootstocks.

Potential of Neglected and Underutilized Yams (Dioscorea spp.) for Improving Nutritional Security and Health Benefits.

Food and nutritional security are the major concerns in many countries of the world and may have potential to contribute to sustainable food systems under climate change. To address the food and nutritional insecurity, it has become extremely important to diversify the present-day agricultural system as well as to search for alternative food and feed ingredients. Some wild root and tuber crops occupy a remarkable position toward food security of the developing world due to their high calorific value and superior carbohydrate content. Yam (Dioscorea spp.) provides food and medicines to millions of people in the world especially in the tropics and sub tropics. It is recognized as the fourth most important tuber crop after potatoes, cassava, and sweet potatoes. It contributes about 10% of the total root and tubers production around the world. Yams also considered as famine food and plays a prime role in the food habit of small and marginal rural families and forest-dwelling communities during the food scarcity periods. These species are unique for their food, medicinal and economic values but their wider utilization is limited due to the presence of anti-nutritional compositions. This paper describes the ethnobotany of yam species in relation to their nutritional, anti-nutritional and pharmacological properties and highlights the potentiality for food and nutritional security for combating the “hidden hunger” caused by micronutrient deficiencies.

Vertical distribution and production of fine roots in an old-growth forest, Japan

Fine roots (≤ 2 mm in diameter) account for up to 50% of total net primary production in forests, representing a major flow of both carbon and nutrients into the soil. We investigated the vertical distribution and production of fine roots in a warm temperate old-growth evergreen broadleaved forest in southwestern Japan. We used a continuous inflow method that considered different rates of diameter-dependent root mortality, decomposition, and thickening. Fine roots were classified into two classes (≤ 1 mm and 1–2 mm diameter). The experiment was conducted over a 1-year period to collect data on the mass of live fine roots and mass of dead fine roots in January, May, November and the following January. Decomposition ratios were assessed for three intervals (January to May, May to November, and November to January). More than 70% of fine roots occurred in the 0–20 cm soil layer, and less than 4% were found in the 50–80 cm soil layer. Decomposition ratios varied seasonally in both root size classes, peaking in summer and reaching a minimum in winter. The same pattern was found for production, mortality, and decomposition. The peak rate of production was 1.62 g·m–2·day–1 in ≤ 1 mm and 0.63 g·m-2·day–1 in 1–2 mm fine roots. The lowest production was 0.62 g·m–2·day–1 in ≤ 1 mm and 0.38 g·m–2·day–1 in 1–2 mm fine roots. Total fine root production over a 1-year period was 6.61 t·ha–1. A mass of 2.70 t·ha–1yr–1 of dead fine roots was decomposed to return nutrients to the soil. It is concluded that a warm temperate old-growth evergreen broadleaved forest in southwestern Japan plays an important role in carbon cycle and nutrient return through a high amount of production and decomposition.

Temperature and moisture dependence of daily growth of Scots pine (Pinus sylvestris L.) roots in Southern Finland.

Scots pine (Pinus sylvestris L.) is one of the most important conifers in Northern Europe. In boreal forests, over one-third of net primary production is allocated to roots. Pioneer roots expand the horizontal and vertical root systems and transport nutrients and water from belowground to aboveground. Fibrous roots, often colonized by mycorrhiza, emerge from the pioneer roots and absorb water and nutrients from the soil. In this study, we installed three flatbed scanners to detect the daily growth of both pioneer and fibrous roots of Scots pine during the growing season of 2018, a year with an unexpected summer drought in Southern Finland. The growth rate of both types of roots had a positive relationship with temperature. However, the relations between root elongation rate and soil moisture differed significantly between scanners and between root types indicating spatial heterogeneity in soil moisture. The pioneer roots were more tolerant to severe environmental conditions than the fibrous roots. The pioneer roots initiated elongation earlier and ceased it later than the fibrous roots. Elongation ended when the temperature dropped below the threshold temperature of 4 °C for pioneer roots and 6 °C for fibrous roots. During the summer drought, the fibrous roots halted root surface area growth at the beginning of the drought, but there was no drought effect on the pioneer roots over the same period. To compare the timing of root production and the aboveground organs’ production, we used the CASSIA model, which estimates the aboveground tree carbon dynamics. In this study, root growth started and ceased later than growth of aboveground organs. Pioneer roots accounted for 87% of total root productivity. We suggest that future carbon allocation models should separate the roots by root types (pioneer and fibrous), as their growth patterns are different and they have different reactions to changes in the soil environment.

Effects of Microtopography on Absorptive and Transport Fine Root Biomass, Necromass, Production, Mortality and Decomposition in a Coastal Freshwater Forested Wetland, Southeastern USA

Forested wetlands are an important carbon (C) sink. Fine roots (diameter < 2 mm) dominate belowground C cycling and can be functionally defined into absorptive roots (order 1–2) and transport roots (order ≥ 3). However, effects of microtopography on the function-based fine root dynamics in forested wetlands are poorly understood. We studied fine root biomass allocation and biomass, necromass, mass loss rate, production, mortality and decomposition of absorptive and transport roots in hummocks and hollows in a coastal plain freshwater forested wetland (FFW) in the southeastern USA using dynamic-flow method. Biomass ratios of first- to second-order roots and absorptive to transport roots and the biomass and necromass of absorptive and transport roots were significantly higher in top 0–10 cm organic peat layer than in 10–20 cm muck and mineral layer, and were significantly higher in hummocks than in hollows. The mass loss rate, production, mortality and decomposition were significantly higher in hummocks than in hollows. Absorptive roots did not have a lower mass loss rate than transport roots. Microtopography significantly affected the contributions of absorptive and transport roots to the total production, mortality and decomposition. Production, mortality and decomposition of absorptive roots were higher than those of transport roots in hummocks but lower than those of transport roots in hollows. Total (hummocks plus hollows) fine root production, mortality and decomposition were 455 ± 106 g m−2 y−1, 475 ± 79 g m−2 y−1 and 392 ± 60 g m−2 y−1, respectively. Greater mortality than decomposition resulted in net fine root C input to soil. The observed microtopographic controls on fine root dynamics have great implications for soil C cycling. As sea level rises, the relative area of hollows in coastal plain FFWs will increase, causing a decrease in fine root mass loss rate, biomass, production, mortality and decomposition and it is the balance of these processes that will determine future soil C storage and cycling.

Root growth dynamics during recovery of tropical mountain forest in North-east India

Ever increasing pressures on tropical forests worldwide due to anthropogenic disturbances have greatly affected both above- and belowground functioning of these forests. While fine roots play major ecological roles in forests through assisting in nutrient and water uptake and returning elements to the soil environment, coarse roots play an important role in C sequestration. We studied changes in fine and coarse root biomass, production, turnover and carbon and nitrogen return to the soil in two regenerating forest stands (RFs) following stone-mining that were 5 years (RF-5) and 15 years (RF-15) post-disturbance compared with a natural forest stand (NF) in Mizoram, North-east India. Fine (§2 mm) and coarse root (2-10 mm) biomass differed significantly among the forest stands and ranged from 239 (RF-5) to 415 (NF) and 230 (RF-5) to 436 (NF) g m−2, respectively. Total root (fine + coarse) biomass increased during stand development but the proportion of very fine root (<0.5 mm) to total root production decreased. Fine root biomass decreased with increasing soil depth. Fine and total root biomass showed strong seasonal correlations with soil moisture, more so than for rainfall and temperature, whereas these relationships were less clear for the coarse root biomass. The amount of N (25–55 kg ha−1) and C (1.9–3.6 t ha−1) stored in root biomass increased with stand age with a corresponding increase in production and turnover of C and N to the soil. Disturbance to these tropical forests negatively affected root dynamics, influenced their spatio-temporal patterns, and reduced the production, amount and availability of nutrients returned to the soil along with a strong reduction in the root biomass carbon pool and sequestration in carbon residence time. We observed that root growth, especially fine roots, is dependent on abiotic variables, and plays a significant role in early stages of secondary succession by adding organic matter and nutrients through high turnover rates in these forests.

Seasonal Patterns of Root Production with Water and Nitrogen Additions Across Three Dryland Ecosystems

Root production is known to contribute at least 50% of total net primary production in dryland ecosystems, yet few studies have addressed seasonal dynamics of root production or the belowground response to altered resource availability. We aimed to identify how root production varies across three dryland ecosystems dominated by different plant functional types: the shortgrass steppe, dominated by C4 perennial bunchgrasses, the northern mixed-grass prairie, co-dominated by perennial C3 and C4 grasses, and the sagebrush steppe, dominated by a perennial shrub with an understory of C3 and C4 grasses and forbs. We also sought to determine how root production changes throughout a growing season for these three systems, and how it responds to increased water and nitrogen availability. We used root ingrowth cores to monitor root production in 6-week intervals between June 1 and October 5, 2017, and with water and nitrogen additions in shortgrass steppe, mixed-grass prairie, and sagebrush steppe in the western Great Plains of the United States. We found that the northern mixed-grass prairie had the highest total root production during our sampling period, and that seasonal patterns of root growth varied significantly across the dryland types, with root growth greatest during the middle of the growing season at the sagebrush steppe and greatest during the end of the growing season at the northern mixed-grass prairie. As expected, belowground root production was about half aboveground production in all sites. Root production responded less to water and nitrogen addition than did aboveground production.

Agro-biological and economic efficiency in a beetroot (Beta vulgaris L.) production system fertilized with hairy woodrose (Merremia aegyptia (L.) Urb.) as green manure

Beetroot (Beta vulgaris L.) is a tuberous vegetable that is under experimentation in the vegetable production system in Rio Grande do Norte state (Brazil). It is quite demanding, in nutritional terms. One of the alternatives to meet this need is green manuring using spontaneous species of the Caatinga biome. The aim of the present work was to optimize the agro-biological performance and economic profitability of the beetroot 'Early Wonder', fertilized with different doses of hairy woodrose (Merremia aegyptia (L.) Urb.) in this semi-arid environment. Hairy woodrose is a spontaneous species of the Caatinga biome that is widely distributed, being found in forests, fences, forest clearings and fields, growing in soils of different textures, producing biomass with a high content of macronutrients. This material was collected from spontaneous vegetation, native to the region, and used as green manure.The experimental design was a randomized complete block, with four treatments and five replicates. The treatments consisted of four amounts of hairy woodrose biomass incorporated into the soil (10, 25, 40 and 55 t ha-1 of dry matter). The following agronomic characteristics were evaluated in each beetroot treatment: plant height, fresh mass of shoots, number of leaves per plant, dry mass of shoots and dry mass of roots, total and commercial root productivity, and root productivity classified into scrap and extra roots, extra A roots, extra AA and great roots. Apart from these characteristics, the following economic indicators were also determined for each treatment: gross income, net income, rate of return and profit margin. The maximum agro-biological efficiency of beet root productivity (22.68 t ha-1) was obtained from 44.92 t ha-1 of hairy woodrose biomass added to the soil. The maximum economic efficiency of the yield of beet roots was achieved as a net income of AU$2,491.00 (R$6,406.36) ha-1, provided by the production of 22.04 t ha-1 of commercial roots, using 37.03 t ha-1 of hairy woodrose biomass incorporated into the soil. The use of hairy woodrose as green manure presents agro-economic feasibility in beet cultivation in this semi-arid environment.

Below- and aboveground production in cocoa monocultures and agroforestry systems

Farmers expect yield reduction of cash crops like cocoa when growing in agroforestry systems compared to monocultures, due to competition for resources, e.g. nutrients and water. However, complementarities between species in the use of resources may improve resource use efficiency and result in higher system performance.Cocoa trees have a shallow rooting system while the rooting characteristics of the associated trees are mainly unknown. This work investigates fine root distribution and production in five cocoa production systems: two monocultures and two agroforestry systems under conventional and organic farming, and a successional agroforestry system. In the organic systems a perennial leguminous cover crop was planted and compost was added, while herbicides and chemical fertilizers were applied in the conventional ones. We measured cocoa fine root parameters in the top 10cm of soil and annual total fine root production at 0–25 and 25–50cm depth. We related the root data with both the aboveground performance (tree and herbaceous biomass), and the cocoa and system yields.Cocoa fine roots were homogenously distributed over the plot area. Around 80% of the total fine roots were located in the upper 25cm of soil. The total fine root production was 4-times higher in the agroforestry systems and the organic monoculture than in the conventional monoculture.The roots of the associated tree species were located in the same soil space as the cocoa roots and, in principle, competed for the same soil resources. The cocoa yield was lower in the agroforestry systems, but the additional crops generated a higher system yield and aboveground biomass than the conventional cocoa monocultures, implying effective resource exploitation. The leguminous cover crop in the organic monoculture competed with the cocoa trees for nutrients, which may explain the lower cocoa yield in this system in contrast with the conventional monoculture.

COMBINATIONS OF CORIANDER AND SALAD ROCKET CULTIVARS IN BICROPPING SYSTEMS INTERCROPPED WITH CARROT CULTIVARS

ABSTRACT The objective of this study was to evaluate combinations of coriander and salad rocket cultivars in bicropping systems intercropped with carrot cultivars in strips under the conditions of Mossoró-RN. The work was conducted at the Experimental Farm Rafael Fernandes from July to December 2014. The experimental design was a randomized complete block design with four replications and treatments arranged in a factorial design with additional treatments of type 2 x 2 x 2 + 2. The treatments consisted of the combinations of two coriander cultivars (Verdão and Português) and two rocket cultivars (Cultivada and Folha Larga), intercropped with two carrot cultivars (Brasília and Esplanada) plus two additional treatments, where the first are the cultivars in monocropping and the second the types of cropping (single and intercropped). We evaluated fresh and dry shoot mass in coriander and rocket and fresh and dry shoot mass as well as dry root mass, commercial and total root productivity, and classified root productivity in carrot. In the intercropping systems we evaluated land equivalent ratio, productive efficiency index, and score of the canonical variable, besides the indicators of economic efficiency (gross income, net income, rate of return and profit margin). Highest agroeconomic efficiency in intercropping systems was achieved with the combination of the coriander cultivar 'Verdão' and the rocket cultivars 'Folha Larga' or 'Cultivada' as well as the carrot cultivars 'Brasília' or 'Esplanada'. Regardless of the tested cultivar combinations, systems with coriander and salad rocket intercropped with carrot showed higher efficiency than monocropping systems.