Boundary Line Approach Research Articles

Valores de referência para diagnose nutricional da palma-forrageira ‘Gigante’ pelo método da linha de fronteira

Abstract The objective of this work was to determine reference values for nutritional diagnosis of ‘Gigante’ cactus pear cultivated with organic fertilization under semi-arid conditions by boundary line approach. The contents of nutrients, determined in samples collected in newly mature cladodes, dry matter yield (DMY), and nutrient extraction of 72 plots of an experiment with ‘Gigante’ cactus pear, fertilized with cattle manure, were used to establish the reference values. The lower (L1) and upper (Lu) limits of the reference values were determined by fitted regression of DMY (y) as a function of nutrient contents in cladodes (x), considering a percentage of the maximum dry matter yield (slope = 0). The reference values, established by boundary line approach for macronutrients and micronutrients, are accurate for the nutritional diagnosis of ‘Gigante’ cactus pear and determine classes for interpretation of nutritional status. The normal reference values established for macronutrients, in g kg−1, are: N (≤11.2 – <19.0), P (≤1.0 – <2.1), K (≤26.7 – <44.2), S (≤0.9 – <2.1), Ca (≤22.1 – <32.6), and Mg (≤9.1 – <13.0); and micronutrients, in mg kg−1, are: B (≤21.6 – <33.5), Cu (≤1.7 – <4.8), Fe (≤49.0 – <125.4), Mn (≤0.0 – <680.4), Zn (≤28.3 – <80.6), and Na (≤19.3 – <72.2).

Obtaining reference values for nutrients in vineyard soils through boundary line approach using Bayesian segmented quantile regression on commercial farm data

Inefficient use of fertilizers in agriculture is a major issue in global food production as it hampers economic viability of farms and offers great risk of environmental pollution. Fertilizing recommendations are guided by plant nutritional assessments, which are compared to reference values so that decisions can be made regarding which nutrient and how much is to be supplied. Traditionally, these values are obtained by field trials that are particularly long and expensive for perennial crops such as grapevines. This research evaluated the use of boundary line (BL) approach and Bayesian segmented quantile regression (BSQR) in determining reference values for nutrients in vineyard soils using commercial farm data. Critical levels (CL) and sufficiency ranges (SR) of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), copper (Cu), zinc (Zn), boron (B) and manganese (Mn) were estimated using datasets from a winery in the Campanha Gaúcha region, Rio Grande do Sul, Brazil. Results indicated lower P and higher K, S, Zn and Mn levels, as compared to current state recommendations. Great inconsistencies were found in CL estimates for Cu and, to a lesser extend, Ca and Mg. Model assessments indicated that BSQR estimates were highly sensitive to quantile selection but poorly affected by changes in the prior. Data simulated using fitted models were consistently over-dispersed. Allowing for variable slopes and intercepts may partition data variability more properly, leading to better fit, higher parameter precision and greater accuracy of estimates. Despite current limitations, the BSQR model provides a flexible framework for BL analysis, enabling the use of commercial datasets in establishing reference values to support group- and site-specific recommendations, a valuable contribution to increase efficiency and sustainability of grapevine fertilization.

Determination of optimal soil pH and nutrient concentrations for cultivated rooibos tea using the boundary line approach

Optimal soil pH and nutrient conditions for rooibos cultivation in South Africa have not yet been established as limited field research has been conducted. Soil chemical (0–300 mm) and yield data were collected from 120 commercial rooibos plantations in the main (170 km wide) production region in the Western and Northern Cape Provinces. The optimum and 90%-yield sufficiency soil ranges were determined using the boundary line approach and quadratic regression. The optimum (sufficiency range) soil chemical properties were a pH (KCl) of 4.5 (4.2–4.7), electrical conductivity of 0.23 mS m−1 (0.16–0.30 mS m−1) and acid saturation of 27.5% (17.1–37.8%). The optimum (sufficiency range) soil available macro- and micronutrients (in mg kg−1) were: 16.9 (7.4–26.4) for P, 20.8 (11.5–30.0) for K, 140.3 (95.9–184.7) for Ca, 50.0 (32.3–63.7) for Mg, 8.3 (4.9–11.7) for S, 34.6 (17.2–52.1) for Fe, 5.5 (2.2–8.8) for Mn, 0.30 (0.16–0.45) for Zn, 0.11 (0.07–0.15) for Cu and 0.11 (0.06–0.16) for B. The resultant optimal values for soil pH and available P, K and Mg corresponded with previous published reports on cultivated fynbos species, while published values were not available for the other parameters. The findings of this study are important for sustainable soil fertility management in commercial rooibos tea production in South Africa.

Determination of foliar nutrient sufficiency ranges in cultivated rooibos tea using the boundary-line approach

Despite the global importance of rooibos tea (Aspalathus linearis (Burm.f.) R.Dahlgren) as a health-promoting crop, foliar nutrient sufficiency ranges have not yet been determined for commercially cultivated rooibos. Determination of these ranges is critical for assessing plant nutrient status and maximising productivity. The aim of this study was to determine optimal rooibos foliar macro- and micronutrient ranges using the boundary-line approach (BLA) method across the main rooibos production areas in South Africa. Foliar nutrient and yield data were collected from 120 different commercial rooibos plantations in the six main rooibos producing areas of the country: Nardouwsberg/ Agterpakhuys, Clanwilliam, Gifberg/ Vanrhynsdorp, Nieuwoudtville, Citrusdal and Sandveld. The BLA-derived optimum (late winter) rooibos foliar macronutrient and 90%-yield sufficiency range concentrations (%) were: 1.55 (1.30–1.80) for N, 0.12 (0.09–0.14) for P, 0.54 (0.34–0.75) for K, 0.20 (0.14–0.26) for Ca, 0.22 (0.19–0.25) for Mg, and 0.10 (0.08–0.11) for S. Optimum micronutrient contents and ranges (mg kg−1) were: 85.8 (57.6–114.1) for Fe, 58.2 (26.9–113.8) for Mn, 16.6 (12.7–20.5) for Zn, 2.8 (1.3–4.2) for Cu, and 26.9 (21.8–32.0) for B. Maintaining foliar nutrient concentrations within these ranges will support maximal yields (1 200 kg ha−1). The foliar nutrient guidelines are of importance for enhancing sustainable rooibos production in South Africa.

Establishment of nutrient sufficiency ranges in olive using boundary-line approach

The establishment of optimum nutrient concentrations provides excellent knowledge for the diagnosis and correction of plant nutritional status to maximize yield. This study was conducted to determine the optimum values and sufficiency ranges of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in olive trees grown in various land forms in Egypt by boundary-line approach. Over two consecutive years, foliar samples from 266 olive trees were collected from different growing areas in Egypt and fruit yields per tree were reported. The derived optimum concentrations for these nutrients by solving the first derivation of the inferred second-degree polynomial functions of the relationship between fruit yield and leaf nutrient concentrations were 1.54% for N, 0.19% for P, 0.87% for K, 1.48% for Ca, 0.22% for Mg, 125 ppm for Fe, 33.7 ppm for Mn, 23.5 ppm for Zn, and 8.6 ppm for Cu. Sufficiency ranges corresponding to 90% of the maximum fruit yield were 1.29%–1.80%, 0.14%–0.24%, 0.66%–1.08%, 1.09%–1.90%, 0.10%–0.33%, 63–165 ppm, 30.2–35.9 ppm, 16.6–30.2 ppm, and 2.8–13.9 ppm, respectively. Since standards of optimum nutrition are not readily available in Egypt and in similar places, the current study provides an important guideline for diagnosing olive trees nutritional status.

Boundary-Line Approach micro-nutrient optimum concentrations and sufficiency ranges for Opuntia ficus-indica (L.) Miller fruiting

Optimum concentrations and/or sufficiency ranges of nutrients are useful for correct diagnosis and improvements of nutrient status of cultivated plants. However, Opuntia ficus-indica nutrient storage at plant and cladode levels and best fit plant requirements for fruiting remain practically unknown. Then, this research work aimed to identify the Boundary-Line Approach (B-LA) micronutrient optimum concentrations linked to maximum fruit yield per one-year old fructification cladode and sufficiency ranges at 90% maximum fruit yield for O. ficus-indica variety ‘Rojo Pelón’. Four years (2012 – 2015) data of fruit yield per cladode and micronutrient concentrations (B, Cu, Fe, Mn, and Zn) were used for the elaboration of scatter diagrams (n = 228) and selection of 7 to 10 points to estimate the B-LA quadratic functions. Then, the vertices allowed estimation of the optimum micronutrient concentrations: B = 33.62 mg kg–1, Cu =11.74 mg kg–1, Fe = 108.51 mg kg–1, Mn = 149.33 mg kg–1 and Zn = 414.91 mg kg–1 as linked to estimated maximum yield per cladode; and the sufficiency ranges at 90% maximum fruit yield: B = 24.44 to 46.25 mg kg–1, Cu = 8.68 – 15.87 mg kg–1, Fe = 73.73 – 143.3 mg kg–1, Mn = 114.89 – 183.77 mg kg–1 and Zn = 334.31 – 514.95 mg kg–1. The linked estimated maximum fruit yield per cladode varies from 1999.48 g to 2139.59 g. The proposed B-LA standards can be used to perform reliable micronutrient diagnosis and proper fertilization recommendations.

Establishing optimal nutrient norms in leaf and soil for oil palm in India

Diagnosis and recommendation integrated system (DRIS)-based critical and optimum leaf nutrient standards for oil palm (OP) (Elaeis guineensis Jacq) have been estimated for some locations of India to find out the most critical nutrients. However, a well-established boundary line approach has not been evaluated for defining optimal ranges of leaf nutrients. Further, no defined standards are available for soil available nutrients in oil palm growing regions of India. Nutrient management in oil palm gains paramount importance due to its huge requirement as well as its spectacular influence on fresh fruit bunch (FFB) and oil yields. Therefore, apt norms need to be established for better productivity through precise nutrient management. With this objective, optimum concentrations for the most important leaf nutrients, their sufficiency ranges, nutrient ratios and their optimal ranges have been determined by employing boundary line approach and the results have been compared with that of DRIS approach based on average values of high yielding populations. Similarly, optimal soil available nutrient status in terms of optimal concentrations and their sufficiency ranges also have been standardized for oil palm and compared with DRIS method. For Krishna – Godavari basin area of Andhra Pradesh in India, the optimal concentrations of nutrients in oil palm leaves were established as 2.64, 0.16, 0.78, 1.3, 0.52, 0.16% for nitrogen (N), phosphorus (P), potassium (K), Calcium (Ca), Magnesium (Mg) and sulphur (S). For boron (B) the optimal concentration is 69.8 mg kg−1 through BLA approach. For the same area, the optimal values of soil available nutrients were 452, 144, 388 kg of N, P2O5 and K2O per ha, 1.96 and 1.7 meq 100 g−1 of Ca and Mg respectively, and 68 mg kg−1 for SO4-S and 8.4 ppm for B. The optimal pH level was 6.6. A variation of up to 10% was recorded between DRIS and boundary line approach and for better management optimal nutrient standards need to be established for each agro-eco region.

Potential nutrient-response curves and sufficiency ranges for ‘Prata-Anã’ banana cultivated under two environmental conditions

ABSTRACT: Proper plant nutrition is critical to increasing the yield of bananas. The objective was to establish the potential nutrient-response curves and sufficiency ranges using the boundary line approach (BLA) and the method proposed by Kenworthy (MK) to assess the nutritional status of ‘Prata-Ana’ bananas cultivated under two environmental conditions. The study was carried out using a database comprising leaf nutrient concentrations and banana yields grown at Missao Velha, Ceara, and Ponto Novo, Bahia, Brazil. The reference population consisted of high-yielding plants with yields greater than the mean yield plus 0.5 standard deviation. The database was divided into two datasets. One contained 253 leaf analysis results and a reference population with a mean yield greater than 39.81 t ha−1 yr−1 at Missao Velha. The other contained 147 samples and a reference population with a mean yield greater than 41.69 t ha−1 yr−1 at Ponto Novo. The sufficiency ranges obtained by the BLA for ‘Prata-Ana’ banana in Bahia and Ceara, respectively, are: a) for macronutrients (g kg−1): N (19.3-22.0) and (19.9-22.1); P (1.4-2.0) and (1.4-1.6); K (22.6-32.2) and (24.0-31.3); Ca (4.6-6.5) and (5.3-5.8); Mg (1.8-2.6) and (2.1-2.7); S (1.3-2.0) and (1.3-1.5); b) for micronutrients (mg kg−1): B (8.4-13.0) and (13.7-16.4); Cu (5.6-8.4) and (4.4-5.2); Fe (54.2-77.6) and (39.0-55.0); Mn (140.1-222.8) and (64.0-91.0); Zn (13.5-18.3) and (12.4-14.5). The sufficiency ranges obtained by the BLA are more assertive when assessing the nutritional status for ‘Prata-Ana’ banana.

Potential nutrient-response curves and sufficiency ranges of ‘Grande Naine’ banana cultivated in two environment

Abstract Adequate plant nutrition is essential to attain higher yields. The objective was to determine potential-nutrient response curves and sufficiency ranges using the boundary line approach and balance indices of Kenworthy for interpreting the nutritional status of ‘Grand Nain’ banana cultivated in two environments. The study was carried out using a database containing leaf nutrient concentrations and yields of bananas cultivated on two areas located in Missão Velha-CE, and Ponto Novo-BA, Brazil. Plots with high-yielding plants, which were those with yields above average plus 0.5 standard deviation, were used atem as reference population. The database was subdivided into two sets. One of them contained 46 leaf tissue samples and reference population with yield greater than 58.84 Mg ha-1 year-1, in Missão Velha-CE. The second data set contained 19 samples and reference population with yield greater than 76.12 Mg ha-1 year-1 in Ponto Novo-BA. Potential response curves were fitted to the relationship between relative yield and leaf element concentrations and balance indices of Kenworthy. Models expressed high predictive power. Sufficiency ranges for macro- and micronutrient concentrations and balance indices of Kenworthy were established. The ranges allow an improved nutritional status assessment of irrigated ‘Grand Nain’ bananas.

Boundary-Line Approach Macro-Nutrient Standards for Opuntia ficus-indica (L.) Miller Variety “Rojo Pelón” Fruiting

The aim of this research work was to identify the Boundary-Line Approach (B-LA) macro-nutrient optimum concentrations linked to maximum yield and sufficiency ranges at 90% maximum yield per 1-year-old fructification cladode for Opuntia ficus-indica (L.) Miller variety “Rojo Pelon”. Four years’ (2012–2015) data of yield per fructification cladode and macro-nutrient concentration [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), or magnesium (Mg)] were used to elaborate bivariate scatter diagrams (n = 228). Selection from 9 to 11 points was performed to estimate quadratic functions as boundary-lines in each bivariate scatter diagram. The vertices allowed estimation of the optimum macro-nutrient concentrations: ln N = 2.32 (10.20 g kg−1), P = 3.04 g kg−1, K = 35.18 g kg−1, Ca = 36.65 g kg−1, Mg = 13.83 g kg−1. The target maximum yield per fructification cladode varies between 1901.13 and 1984.41 g. The estimated sufficiency ranges at 90% of the maximum yield are ln N = 2.07–2.59 (7.86–13.40 g kg−1), P = 2.54–3.54 g kg−1, K = 25.36–45.01 g kg−1, Ca = 27.96–45.35 g kg−1, and Mg = 10.3–17.38 g kg−1. These nutrient standards may be used as a reference for maximizing yield per fructification cladode in O. ficus-indica, specifically for the variety “Rojo Pelon”.

Optimizing agronomic practices for closing rapeseed yield gaps under intensive cropping systems in China

A yield gap analysis for rapeseed (Brassica napus L.) is critical to meeting the oil demand by identifying yield potential and yield constraints. In this study, potential yield (Yp), attainable yield (Yatt), and actual yield (Yact) for winter rapeseed were determined in five different zones of China. A boundary line approach was adopted to calculate Yp, based on a large-scale field experimental database. A meta-analysis was conducted on the data obtained from 118 published studies to evaluate the effects of agronomic factors on rapeseed yield. The main results indicated that farmers only achieved 37–56% of the yield potential across the zones. The low altitude areas (L-URY) and lower reaches (LRY) of the Yangtze River Basin (YRB), China had high yield levels. The total yield gap was 1893 kg ha–1, due to the agronomic management factors, environmental factors, and socioeconomic factors. The meta-analysis showed that weed control and drainage were the best management practices to improve yields (45.6 and 35.3%, respectively), and other practices improved yields by 17.1–21.6%. Consequently, to narrow the yield gap over the short term, the study could focus on techniques that are easily implemented to farmers.

The utility of a boundary line approach for simulating denitrification and nitrous oxide emissions from a Regosol under summer maize-winter wheat crop rotation in Southwest China

Despite the ever-increasing measurements of denitrification and nitrous oxide (N2O) emissions globally, boundary line analyses of these important processes have only been applied to a limited number of agroecosystems. The primary aims of this study were to determine the responses of denitrification and N2O emissions from a subtropical cropland to several soil parameters through boundary line analyses, and to evaluate the ability of site-specific boundary line models for simulating gaseous nitrogen (N) losses using available soil parameters. We performed 403 measurements of denitrification and N2O emissions from two fields cropped with a winter wheat-summer maize rotation in the Sichuan Basin, Southwest China, from October 2004 to September 2005. Boundary lines were fitted for denitrification and N2O emission data against soil temperature, water content, ammonium and/or nitrate substrates, and heterotrophic respiration rates. The boundary lines were largely in agreement with existing theoretical concepts. By incorporating the regulatory effects of soil temperature, water content, N substrates, and an unknown factor that could be related to ammonium content, the boundary line models reasonably simulated the seasonal variations in denitrification and N2O emissions that were collected from a field trial in the same region during the maize season in 2012. The models overestimated the denitrification and N2O emissions on the sampling dates by 8% and 22% on average, respectively. We conclude that boundary line models are useful tools for estimating gaseous N losses from a given cropland. However, the application of the models is limited by the availability of input data.

Identifying the limiting factors driving the winter wheat yield gap on smallholder farms by agronomic diagnosis in North China Plain

North China Plain (NCP) is the primary winter wheat production region in China, characterized by smallholder farming systems. Whereas the winter wheat average yield of smallholder farmers is currently low, the yield potential and limiting factors driving the current yield gap remain unclear. Therefore, increasing the wheat yield in NCP is essential for the national food security. This study monitored wheat yield, management practices and soil nutrient data in 132 farmers' fields of Xushui County, Baoding City, Hebei Province during 2014–2016. These data were analyzed using variance and path analysis to determine the yield gap and the contribution of yield components (i.e., spikes per hectare, grain number per spike and 1000-grain weight) to wheat yield. Then, the limiting factors of yield components and the optimizing strategies were identified by a boundary line approach. The results showed that the attainable potential yield for winter wheat was 10 514 kg ha−1. The yield gaps varied strongly between three yield groups (i.e., high, middle and low), which were divided by yield level and contained 44 farmers in each group, and amounted to 2493, 1636 and 814 kg ha−1, respectively. For the three yield components, only spikes per hectare was significantly different (P<0.01) among the three yield groups. For all 132 farmers' fields, correlation between yield and spikes per hectare (r=0.51, P<0.01), was significantly positive, while correlations with grain number per spike (r=−0.16) and 1000-grain weight (r=−0.10) were not significant. The path analysis also showed that the spikes per hectare of winter wheat were the most important component to the wheat yield. Boundary line analysis showed that seeding date was the most limiting factor of spikes per hectare with the highest contribution rate (26.7%), followed by basal N input (22.1%) and seeding rate (14.5%), which indicated that management factors in the seeding step were the most important for affecting spikes per hectare. For desired spikes per hectare (>6.598 × 06 ha−1), the seeding rate should range from 210–300 kg ha−1, seeding date should range from 3th to 8th October, and basal N input should range from 90–180 kg ha−1. Compared to these reasonable ranges of management measures, most of the farmers' practices were not suitable, and both lower and higher levels of management existed. It is concluded that the strategies for optimizing yield components could be achieved by improving wheat seeding quality and optimizing farmers' nutrient management practices in the NCP.

Developing sustainable summer maize production for smallholder farmers in the North China Plain: An agronomic diagnosis method

With an increasing population and changing diet structure, summer maize is increasingly becoming an important energy crop in China. However, traditional farmer practices for maize production are inefficient and unsustainable. To ensure food security and sustainable development of summer maize production in China, an improved, more sustainable farmer management system is needed. Establishing this system requires a comprehensive understanding of the limitations of current farming practice and the ways it could be improved. In our study, 235 plots from three villages in the North China Plain (NCP) were monitored. Maize production on farms was evaluated; our results showed that the maize yield and nitrogen partial factor productivity (PFPN) were variable on smallholder farms at 6.6–13.7 t ha−1 and 15.4–88.7 kg kg−1, respectively. Traditional farming practices also have a large environmental impact (nitrogen surplus: −64.2–323.78 kg ha−1). Key yield components were identified by agronomic diagnosis. Grain yield depend heavily on grain numbers per hectare rather than on the 1000-grain weight. A set of improved management practices (IP) for maize production was designed by employing a boundary line (BL) approach and tested on farms. Results showed that the IP could increase yield by 18.4% and PFPN by 31.1%, compared with traditional farmer practices (FP), and reduce the nitrogen (N) surplus by 57.9 kg ha−1. However, in terms of IP effect, there was a large heterogeneity among different smallholder farmers' fields, meaning that, precise technologies were needed in different sites especially for N fertilizer management. Our results are valuable for policymakers and smallholder farmers for meeting the objectives of green development in agricultural production.

Boundary line approach applied among crop emergence parameters and soil physical properties

ABSTRACT The boundary line technique has been proposed for interpreting biological data where one variable is a biological response and the other is an independent variable. The objective of this study was to correlate maize and soybean emergence parameters with soil seedbed physical properties using a boundary line approach. The study was performed at the experimental farm belonging to the Universidade Estadual de Ponta Grossa, in the municipality of Ponta Grossa, Paraná State, Brazil. The area has been managed under a no-tillage system for 18 years. The emergence percentage (EP) and emergence rate (ER) were determined for maize and soybean crops. Soil seedbed physical properties were evaluated for both crop species and included soil penetration resistance, volumetric water content, aggregate stability, tensile strength, friability, saturated soil hydraulic conductivity, bulk density, and the least limiting water range. The boundary line approach was applied to pairs of values of plant emergence parameters and soil seedbed physical properties, and then the regression model was adjusted to the boundary points. The boundary line approach indicated that crop emergence was dependent on soil seedbed physical properties. It was possible to determine the optimum values of soil seedbed physical variables for crop emergence. The boundary line approach is a promising and complementary tool to better understand crop emergence responses to soil seedbed physical properties.

Nutrient sufficiency levels for haskap (Lonicera caeruleaL.) using the boundary-line approach

Adequate supply of plant nutrients is crucial for haskap plant growth and increased productivity. A study was carried out to determine the variability in haskap (Lonicera caerulea L. cv. Indigo Gem) plant characteristics in relation to soil and leaf tissue nutrient status. A total of 19 composite soil samples and corresponding plant leaf tissue samples were collected in 2016 from 12 locations in Nova Scotia. Plant parameters measured include growth rate, leaf size, leaf chlorophyll content, and visual observations. A boundary-line approach was used to determine nutrient sufficiency ranges in leaf tissues of 2.23%–2.96% for N, 0.22%–0.28% for P, 0.84%–1.32% for K, 1.63%–2.10% for Ca, and 0.14%–0.50% for Mg. Principal component and correlation analysis suggested a possible antagonistic interaction between leaf K and Mg. Negative associations were observed most frequently between Ca and Mg and other nutrients, especially K. Plant parameters such as bush volume, leaf size, and growth rate were closely related to soil and leaf K. Deficiencies in leaf tissue K and P were identified as potentially important factors limiting growth. Therefore, there is a need to adjust or balance the application of these nutrients. In conclusion, the sufficiency ranges derived can be used as a guiding principle in diagnosing the nutritional status of haskap cv. Indigo Gem on representative farms in Nova Scotia.

The disturbance regime of an Early Holocene swamp forest in the Czech Republic, as revealed by dendroecological, pollen and macrofossil data

A unique remnant of forest dating back to the period 9733–7897 yr BC and consisting of hundreds of tree bases was discovered in the Czech Republic. We aimed to reveal the complex disturbance history of this (sub)fossil forest using dendrochronology, and to describe its detailed plant species composition changes using palaeobotanical techniques. Analysing such Early Holocene forest dynamics should help us understand the ability of the forest community to actively adapt to climate change and generally to understand the role of dynamic instability in ecosystem evolution.We anatomically identified woody species in 488 samples, and determined the ages, growth suppressions, releases and fire scars in 116 well preserved tree ring series using a modern boundary line approach. This image of the forest structure and dynamics was supplemented with analyses of pollen spectra and plant macrofossils in excavated profiles. In order to achieve accurate dating, we dated 87 samples using 14C and synchronized tree ring series, and compared them with an existing Pinus sylvestris chronology.The developmental trajectory of the forest was unique, and did not match the general trend of postglacial pine growth in central Europe. Palaeobotanical proxies indicated that during the circa 2000 years the forest persisted, this Early-Holocene ecosystem passed through several phases, reflected in the species composition of the vegetation as well as in habitat conditions. Nevertheless, the dominance of pine and the complex fine-scale disturbance regime were relatively robust and did not change fundamentally. Low-severity fires and short-term changes in soil moisture regime were crucial disturbance agents in the ecosystem. Stand-replacing disturbances were not found up to the gradual collapse of the forest around 8300 yr BC, replaced by a swamp community. The disturbance regime was relatively stable, suggesting a mitigating effect of changing climate due to the predominance of pine in the forest.

Soil texture affects root penetration in Oxisols under sugarcane in Brazil

Two field trials were set up in Brazil to investigate the effects of soil tillage practices on soil physical condition, root distribution, and sugarcane yield in areas under sandy loam and clayey soils. Additionally, we identified the critical limits for sugarcane root development in soils under contrasting texture using the boundary line approach. The treatments with two tillage practices (conventional tillage - CT and no-tillage - NT) were established in a randomized block design with four replications within two paired areas, one under crop rotation and the other under bare fallow during the sugarcane replanting period. Measurements of soil bulk density (BD), macroporosity (MaP), microporosity (MiP), soil resistance to penetration (Pr), root biomass (RB) and sugarcane yield were performed. Soil MaP and MiP were not affected by the treatments in both soils. The Pr values were higher in NT than CT in both sites, especially in surface layers. For clayey soil, BD values were higher in NT at depths of 0.0–0.1 and 0.1–0.2 m in crop rotation and at the depth of 0.1–0.2 m in bare fallow area. Sugarcane yield for clayey soil (153 Mg ha−1) was more than twice that measured at the sandy soil (58 Mg ha−1). In general, the CT promoted a slight increase root production and did not affect sugarcane yields. In both soil types, most part of RB (60 to 70%) was concentrated near the sugarcane row (horizontal aspect) and within the top 0.4 m of depth (vertical profile), indicating that much of the root system is retained within the planting furrow. Our study demonstrates the potential for using the boundary line method to estimate the effects of BD and Pr on root growth. Root system was severely restricted at sandy soil when BD > 1.70 Mg m−3 and Pr > 1.5 MPa, while for clayey soil the critical values were BD > 1.25 Mg m−3 and Pr > 2.5 MPa. While our study provides valuable insights, we advocate that further studies should be done to better understand the effect of differing levels of BD and Pr for sugarcane yields in soils of different textures.

Nutrient Sufficiency Ranges in Mango Using Boundary-Line Approach and Compositional Nutrient Diagnosis Norms in El-Salhiya, Egypt

ABSTRACTNutrient sufficiency ranges are useful for diagnosing and correcting plant nutritional status in order to optimize yield and protect the environment. This study was conducted to determine nutrient sufficiency ranges for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in mango trees grown in El-Salhiya, Egypt, through boundary-line approach (BLA) and compositional nutrient diagnosis (CND) technique. For this purpose, foliar samples from 310 mango trees were collected during two successive years from the study area and fruit yields were recorded. The nutrient sufficiency ranges generated by BLA were 0.744–1.430% for N, 0.074–0.142% for P, 0.543–1.045% for K, 1.366–2.653% for Ca, 0.155–0.305% for Mg, 389–1148 ppm for Fe, 23.1–60.5 ppm for Mn, 28.4–56.3 ppm for Zn, and 2.37–12.10 ppm for Cu. The CND-derived nutrient sufficiency ranges were 0.917–1.215% for N, 0.066–0.106% for P, 0.585–0.943% for K, 1.003–2.077% for Ca, 0.112–0.378% for Mg, 277.5–849.2 ppm for Fe, 27.9–82.4 ppm for Mn, 29.2–44.6 ppm for Zn, and 2.42–11.37 ppm for Cu. The optimum nutrient concentrations generated from BLA were in general comparable to those obtained using CND technique. Only Ca and Fe optimum concentrations showed poor match. Seven significant nutrient interactions were strongly evidenced through principal component analysis of the computed CND indexes. The positive interaction was P-K, while the negative interactions were P-Mg, K-Mg, Ca-Zn, P-Fe, K-Fe, and Zn-Cu.

Cassava yield loss in farmer fields was mainly caused by low soil fertility and suboptimal management practices in two provinces of the Democratic Republic of Congo

Abstract A better understanding of the factors that contribute to low cassava yields in farmers’ fields is required to guide the formulation of cassava intensification programs. Using a boundary line approach, we analysed the contribution of soil fertility, pest and disease infestation and farmers’ cultivation practices to the cassava yield gap in Kongo Central (KC) and Tshopo (TSH) provinces of the Democratic Republic of Congo. Data were obtained by monitoring 42 and 37 farmer-managed cassava fields during two cropping cycles in KC and one cropping cycle in TSH, respectively. Each field was visited three times over the cassava growing period for the observations. Logistic model was fitted against the observed maximum cassava root yields and used to calculate the achievable yield per field and for individual factor. At field level, the factor that led to the lowest achievable yield (Y up(i)1 ) was considered as the dominant yield constraint. Cassava yield loss per field was expressed as the increase in the maximal root yield observed per province (Y att - attainable yield) compared to Y up(i)1 . Y att was 21 and 24 t ha −1 in TSH and KC, respectively. With the cassava varieties that farmers are growing in the study areas, pests and diseases played a sparse role in the yield losses. Cassava mosaic was the only visible disease we observed and it was the dominant yield constraint in 3% and 12% of the fields in KC and TSH, respectively. The frequent yield constraints were suboptimal field management and low soil fertility. Cultivation practices and soil parameters led to Y up(i)1 in 47% and 50% of the fields in KC, and in 47% and 41% of those in TSH, respectively. Individual soil parameters were the yield constraint in few fields, suggesting that large-scale programs in terms of lime application or recommendation of the blanket fertilisers would result in sparse efficacy. In KC, yield losses caused by low soil fertility averaged 6.2 t ha −1 and were higher than those caused by suboptimal field management (5.5 t ha −1 ); almost nil for cassava mosaic disease (CMD). In TSH, yield losses caused by low soil fertility (4.5 t ha −1 ) were lower than those caused by suboptimal field management (6.5 t ha −1 ) and CMD (6.1 t ha −1 ). Irrespective of the constraint type, yield loss per field was up to 48% and 64% of the Y att in KC and TSH, respectively. Scenario analysis indicated that the yield losses would remain at about two third of these levels while the dominant constraint was only overcome. We concluded that integrated and site-specific management practices are needed to close the cassava yield gap and maximize the efficacy of cassava intensification programs.