Soil Water Tension Research Articles

Study of the habitat, and potential distribution of Himalayan Ginseng (Panax pseudoginseng Wall.), and the diversity of its associated species in Nangkor and Shingkhar Geogs, Zhemgang, Bhutan

Panax pseudoginseng Wall. is a highly sought-after medicinal plant in Bhutan, but little is known about its distribution and habitat in the country. Therefore, this study aimed to determine suitable habitat, and potential distribution of P. pseudoginseng, and the diversity of its associated species in Nangkor and Shingkhar Geogs, Zhemgang, Bhutan. A total of 42 plots were laid using a purposive sampling method. Various parameters like slope, aspect, soil nutrients, soil pH, humidity, temperature, and soil water tension were collected. The Spearman’s correlation test indicated that the temperature and canopy cover had negative association with the counts of P. pseudoginseng. The Spearman's correlation test for NPK indicated that Phosphorus had significant difference with the counts of P. pseudoginseng. A total of 1,277 species distributed in 87 genera of 66 families were recorded including the trees, herbs and pteridophytes. Fagaceae was the most dominant family in the study area. Seven types of forest were classified based on the floristic composition of trees. Potential distribution was obtained using ArcGIS that combined observation data, reclassification and Weighted Overlay. Overall, 95.39% of an area under Zhemgang District is suitable for the growth of P. pseudoginseng.

Morphology, biochemistry, and yield of cassava as functions of growth stage and water regime

Water deficit affects morphological attributes and physiological and biochemical processes important to plants. Although cassava crop is known for its rusticity and adaptability to adverse environmental conditions, there have not been any studies reporting the effects of water deficit at different growth stages on cassava morphology and biochemistry. The objective of this research was to evaluate the morphological, anatomical, biochemical, and yield responses of cassava under different water regimes in three growth stages. The experimental design used was completely randomized 3 × 3 factorial scheme consisting of three growth stages (GS) [90–180 (GS3), 180–270 (GS4), and 270–360 days after planting (DAP) (GS5)] and three soil water tensions (-10, -40, and -70 kPa) with five replicates. Plants were affected, mainly in GS3, by -40 and -70 kPa soil tensions, with decreases in stem diameter, plant height and number of leaves. Leaf anatomy was also affected by water deficit in GS3, with reductions in the mesophyll thickness (13.7%), spongy parenchyma (19.9%), epidermal cells on the blade abaxial surface (18.0%) and in the number of xylem vessels (15.8%); in addition, there was an increase in the wall thickness (105.0%) and in the diameter (85.5%) of the xylem vessels. Under prolonged water deficit, there was an increase in the activity of superoxide dismutase and catalase, which were efficient in controlling H2O2. The imposition of water deficit drastically reduced the yield of commercial and tuberous roots in GS3 (82.1% and 65.0%) and GS5 (45.7% and 32.5%). Our study shows that the period of crop susceptibility to water deficit is longer than previously thought, evidencing the need for greater attention to water availability between 90 and 180 and between 270 and 360 DAP, as it may aid in reducing the negative effects of water deficit on the biochemistry, anatomy, and yield components of cassava.

Low-cost and high-efficiency automated tensiometer for real-time irrigation monitoring

ABSTRACT Knowing the soil moisture available to plants is important for adequate management of water use in agricultural farms, with automated methods being the most accurate. However, acquisition costs are high and most of the commercially available irrigation controllers still work using pre-set times. This study aimed to develop and calibrate a low-cost automated tensiometer with high efficiency in irrigation control, based on real-time monitoring. The research was conducted at the Laboratories of Hydraulics and of Water Soil Plant and Atmosphere Relationship, which belong to the Federal University of Grande Dourados (UFGD), in Dourados, MS, Brazil, with soil classified as an Oxisol. Pressure transducers and a microcontroller were used to assimilate the pressure inside tensiometers and transform it into readings of soil water matric potential (Ψm). Thus, the calibration was carried out by comparing the different readings of the transducer and digital tension meter. Different tensions were applied to obtain a soil moisture curve, starting from the most humid point (saturated) to the driest one (oven-dried soil), collecting 20 valid points. Subsequently, the data were subjected to the normality test, with subsequent statistical analysis and regression curve models. Linear adjustments with a high coefficient of determination (R2 = 0.99) were observed, with the automated system built in this study being capable of monitoring soil water tension in real-time.

Cowpea Root Growth under Water Availability and Co-inoculation with Growth Promoting Rhizobacteria

ABSTRACT Rainfall variations can occur with crops in field condition which can result in soil water restrictions and impair crop development. Inoculation with Azospirillum genus bacteria can be presented as an alternative, as it has the ability to fix N2, promote root growth and produce beneficial metabolites to plants under water stress conditions. Thus, the objective was to co-inoculate A. brasilense and Bradyrhizobium sp. in cowpea and verify the potential to minimizing the effects caused due to water availability on root growth and nodulation. The study was carried out in a greenhouse with completely randomized block design and 4 replications in 4 × 4 factorial arrangement, the treatments being: (i) non-inoculated, (ii) N-fertilizer, (iii) inoculated with Bradyrhizobium sp. and (iv) co-inoculated with Bradyrhizobium sp. + A. brasilense. All treatments were associated with soil water tension of 15, 30, 45 and 60 kPa. Co-inoculation increased dry mass and nodules number. The root surface area and dry mass of cowpea roots showed an increase from the 50.55 kPa tension with co-inoculation.

Biochar had minor effects on yield, quality, and water availability of irrigated alfalfa, corn, and wheat

AbstractOne approach to water optimization in agriculture is to increase soil water retention. A soil amendment that has received attention for its ability to increase soil water retention is biochar, the remaining biomass after high‐C materials have been pyrolyzed. Two studies were conducted in Utah at two sites each during 2018–2020 to evaluate how a fast‐pyrolysis wood biochar influenced the productivity and crop quality of irrigated alfalfa (Medicago sativaL.), corn (Zea maysL.), and wheat (Triticum aestivumL.) along with soil water tension. One study included a single biochar rate of 22 Mg ha−1at two levels of irrigation (full vs. partial), where soil‐incorporated biochar increased silage corn yield by 12% in 2018 and reduced yield by 10% in 2019. Topdressed biochar had no effect on alfalfa yield from 2018 to 2020 in either irrigation rate. The other trial had six to seven biochar rates (0–67 Mg ha−1) plus the addition of wood chips at a single rate (22 Mg ha−1) at one site. This trial displayed a yield decrease of 0.01 Mg ha−1of wheat grain for each additional 1 Mg ha−1of biochar applied; however, there were no effects on silage corn production. Data obtained over 10 site‐years showed minimal effects from this type of biochar on crop yield, quality, or soil water tension, leading us to conclude that this wood biochar was not an effective tool for enhancing short‐term crop production or conserving irrigation water in arid agriculture.

Effect of different soil water tensions and potassium fertilization on the production and quality of netted melon (cucumis melo l.) in the Amazon area

The objective of this study was to evaluate the production and qualitative behavior of netted melon in a protected environment subjected to different soil water tensions and potassium doses, applied via fertigation. The experimental design was randomized blocks (RBD) in a 4 x 5 factorial scheme with 20 treatments and three replicates, consisting of five percentage doses of potassium (0, 50, 100, 150 and 200%) and four soil water tensions (15, 30, 45 and 60 kPa). The variables analyzed were average yield (t ha-1), transverse and longitudinal diameter of fruits (mm), pulp thickness (mm), °Brix (%) and pH. Yield and fruit longitudinal diameter were decreased linearly with the increase in soil water tension. The best result for yield and fruit longitudinal diameter of 51.24 t ha-1 and 127.7 mm were achieved, respectively, when irrigation performed at 15 kPa tension. The lowest value was found at the maximum tension (60 kPa). Regarding potassium doses, a quadratic model fitted to the data, with maximum values of yield and longitudinal diameter at the K2O doses of 235.30 and 232.82 kg ha-1, respectively. The interaction of T x K led to higher values of °Brix under 247.68 and 371.52 kg ha-1 of K2O with tension of 24.67 kPa, with no difference between both. The best result of fruit transverse diameter was observed under combination of 371.52 kg ha-1 of K2O and 15 kPa tension. Irrigation at tension of 15 kPa and K2O dose of 247.68 kg ha-1 can be indicated for the study conditions

Effect of irrigation and nitrogen management on yield, nutrient uptake and water productivity of direct–seeded rice in India

Direct-seeded rice has the potential to address labor and water shortage problems, and avoid possible deleterious effects of puddling on sequence crops. However, the integrated effect of irrigation and nitrogen management on crop and water productivity is not well understood in alluvial soils of India. Therefore, a field study was conducted to evaluate different irrigation thresholds and N split applications on water use and productivity and N use efficiency in DSR. Treatments were established in a split-plot design with three replications . Main plots compared irrigation thresholds based on soil water tension: (i) 0 kPa; (ii) 10 kPa; (iii) 20 kPa; and (iv) 40/10 kPa). Sub plots evaluated N management practices: (i) no N application, (ii) 120 kg N ha−1 as three equal splits, and (iii) 120 kg N ha−1 as four equal splits. Irrigation at 0 and 10 kPa recorded the highest biomass accumulation which decreased by 10-16% with higher water stress. However, irrigation water productivity increased with an increase in water stress. Irrigation at 10 and 20 kPa combined with four N splits resulted in grain yield similar to when irrigation was applied at 0 kPa with three or four N splits. There was a saving of irrigation water up to 17 to 36%, 30 to 46% and 54- 61% with 10 kPa, 20 kPa, and 40/10 kPa, respectively. It was concluded that irrigation at 10 and 20 kPa, and four N splits were beneficial for increasing grain yield and water productivity of DSR.

Using Arduino sensors to monitor vacuum gauge and soil water moisture

Sensors associated with the Arduino board can be an alternative to traditional sensors. The objective of this study was to calibrate a capacitive sensor to measure soil moisture and determine the soil water retention curve (< 100 kPa) using the MPX5100DP pressure transducer in conjunction with capacitive sensor measurements. The soil used was Red Oxisol, which had a clay texture and a bulk density of 1.20 Mg m−3. The model 𝑦𝑦=𝑎𝑎−𝑏𝑏𝑐𝑐𝑥𝑥 was fitted to the capacitive sensor data, which had the following statistical parameters: 9% (MAPE, mean absolute percentage error), 0.025 (RMSE, root-mean-square error), 0.97 (d), and 0.93 (𝑅𝑅2). In general, the error for the retention curves obtained with the capacitive sensor and that obtained by weighing was 0.025 (RMSE). Despite the slight tendency of the capacitive sensor to underestimate the highest values of soil moisture, these sensors can be used as an alternative for measuring soil moisture and water tension.

Development and production of iceberg lettuce irrigated with magnetically treated water

Irrigated agriculture has become a concern, given the scarcity of freshwater. To reduce its water consumption, new techniques and technologies have been proposed. Based on this, the objective of this work was to evaluate the influence of different soil water tensions at initiation of irrigation with magnetically treated water, on ‘iceberg’ lettuce Lucy Brown (Lactuca Sativa L.) development and production. The experiment was conducted in a greenhouse, using a completely randomized factorial design, to evaluate two water types (magnetically treated water – MW and ordinary water – OW) and four soil water tensions at initiation of irrigation (T1 – 15 kPa, T2 – 25 kPa, T3 – 40 kPa and T4 – 70 kPa), with three replicates. Tensiometers were used to estimate soil water tension. The evaluated parameters were: aerial part fresh and dry total mass; commercial head fresh and dry mass, root fresh and dry mass; stem fresh and dry mass; stem length and diameter; percentage of leaves with tip burn, total and commercial yield; water use efficiency related to total and commercial yield; plant exposed area; and dry matter content. Despite achieving greater water use efficiency, the magnetic treatment may have hindered the removal of water from the soil by the crop, especially at increased soil water tension at initiation of irrigation.

Crop Response to Combined Availability of Soil Water and Its Salinity Level: Theory, Experiments and Validation on Golf Courses

The phenomenological expression showing crop yield to be directly dependent on water deficiency, under saline conditions, has encouraged a continued focus on salinity as a viable approach to increase crop yields. This work reassesses crop response to availability of saline soil water ASW in two stages (A) Develop a simple approach suggesting that permanent wilting point (WP) increases under high saline soil water tension and relative yield of Lettuce (Lactuca sativa L., var longifolia Lam., cv. Nevada) and maize (Zea mays L., cv. Jubilee sweet) decrease. (B) Using a deterministic numerical soil water model to validate the theory on Bermuda grass of golf courses. The experimental plots were established in the North Negev, Israel (Sweet corn) and the Algarve, Portugal (Lettuce and Bermuda grass covering the golf courses). Sprinkler irrigation and line source techniques were used for water application, creating a saline gradient under a precise irrigation water distribution. Two salinity empirical models were tested (Mass and Hoffman MH and van Genuchten–Gupta vGG). Their empirical models were modified and instead of soil electrical conductivity of irrigation water (ECe) we used wilting point (WP) and RASW to follow the changes in relative yield. The validation was conducted with theoretical soil plant atmosphere water (SPAW) to predict the results on golf courses. It is concluded that an alternative S-shaped response model provides better fit to our experimental data sets. Modified MH model (Yr = Y/Ymax = a ∗ (ASW–threshold’s constant) revealed that a single dimensionless curve could be used to express yield—salinity interference when represented by varying ASW. The vGG model: vGG can represent salt tolerance of most crops, by using varying wilting point of average root zone salinity, at which the yield has declined by 50%. The abscissa of both models was based on WP rather than the standard soil electrical conductivity (ECw). The correlation between the experimental data and WP or relative available soil water (RASW) was acceptable and, therefore, their usefulness for prediction of relative yield is acceptable as well. The objectives of this study were: 1. To develop a simple model describing the effect of salinity through soil water availability on crop production; 2. To replace the standard varying soil electrical conductivity ECe used by MH and vGG models by two soil parameters (at wilting point- θwp and at field capacity θfc) in order to describe the relationship between them and relative yield. 3. Validate the new model with respect to independent salinity on Golf courses and a mathematical deterministic model.

Ecohydrological implications of the variability of soil hydrophysical properties between two Sphagnum moss microforms and the impact of different sample heights

The ecohydrological and biochemical processes responsible for the globally significant stores of carbon in northern peatlands are largely controlled by the soil’s hydrophysical properties, in particular the relationship that soil water tension (ψ) has with soil water content (θ) and hydraulic conductivity (K). Despite the importance, little is known about how these relationships vary between species in different physiological Sphagnum microforms, such a hummock and hollow, as well as with depth within a profile. Complicating matters is that laboratory experiments to determine these relationships are almost always completed with 5 cm high samples, despite no real scientific evidence supporting this height. To address these shortcomings, we sampled 8 replicates/samples (moss surface to 15 cm depth) each from a S. magellanicum hollow and a S. fuscum hummock. We determined the K(ψ) and θ(ψ) relationships at various pressure heads (0 to –32 cm) and then sub-sectioned the 15-cm samples into 3x5-cm (top, middle, bottom) samples and repeated the tests. There were important differences in both K(ψ) and θ(ψ) relationships between the top, middle and bottom samples. Additionally, comparison of the average of the 3x5-cm samples versus the 15-cm samples suggested that the 15-cm samples were not a good representation due to not being fully compatible with the methodology, and that 3x5-cm samples were preferred. Using Hydrus-1D to simulate a 30-day drought period with local hydroclimatological data, we assessed whether the statistically significant differences were ecohydrologically significant when accounting for the different topographic niches of the two species. The different moss species responded differently, with S. fuscum becoming more water stressed than S. magellanicum, yet S. fuscum lost less water from soil water storage than S. magellanicum. This highlighted the critically important need to replicate the species’ niche in the landscape, and not give two distinct species the same hydrological modelling boundary conditions to compare results.

Competition, stress and benefits: Trees and crops in the transition zone of a temperate short rotation alley cropping agroforestry system

AbstractTree strips on agricultural production sites offer many economic, ecological and social advantages. However, the introduction of trees creates a transition zone between tree strips and crop land. Here, trees and crop plants compete for resources such as space, nutrients, water and light, which causes stress in the low‐competitive system. On the other hand, facilitation such as additional nutrient input through tree leaf litter and fine roots are possible. This study aims to provide indications for competition and benefits that can arise for plants growing in the transition zone of a temperate short rotation alley cropping agroforestry system (SRACS). Various climatic and plant‐growth parameters were investigated between 2013 and 2019 at different positions of an SRACS with fast‐growing poplars in northern Germany. Reduced yield of wheat, oilseed rape and silage maize close to the tree strip was associated with greater soil water tension in 30 and 60 cm soil depth due to the presence of poplar roots, reduced solar radiation due to tree shading and leaf litter coverage. In contrast, poplars growing in the outer rows produced more biomass than those in the inner rows due to the additional availability of space, light and nutrients taken from the crop field. Trees in the transition zone seem to be competitive with arable crops, but without effect on the average long‐term yield of arable crops.

Soil oxygen and water dynamics underlying hypoxic conditions in the root-zone of avocado irrigated with treated wastewater in clay soil

Alternative water sources for agriculture are in high demand in a world with diminishing fresh water (FW) availability. Treated wastewater (TWW) offers a reliable alternative, but increasing evidence is pointing to damage to TWW irrigated orchards planted in clay soils related to soil hypoxia. The mechanisms responsible for this hypoxia have not been extensively studied to date. The aim of this study was to elucidate meaningful insights into the mechanisms responsible for the hypoxia in TWW irrigated orchards planted in clay soils using a novel approach whereby parameters describing the soil oxygen and water temporal dynamics are analyzed. To that end, soil oxygen and soil water tension (SWT) measurements from a two year field experiment comparing TWW to FW irrigation in an avocado orchard planted in a clay soil (60 % clay) were used. The deterioration in oxygen levels occurred as the irrigation season progressed, and the oxygen availability decreased with depth (10–35 cm depth). During August-September, when the lowest oxygen concentrations were measured, the water content at which oxygen supply matched oxygen consumption at 35-cm depth did not differ between treatments (∼50 mbar), but the TWW irrigated soil experienced ∼47 % more time at wetter conditions. Lower oxygen decline rates were observed in the TWW irrigated plots which countered the previous concept that TWW leads to increased soil oxygen consumption. The findings point towards the rate of soil drying as the prime cause of differences – TWW irrigated plots dried in a rate which is nearly 4-times smaller than that in FW irrigated plots during the dark and light hours, reflecting slower drainage and water uptake respectively. It is suggested that soil hypoxia induced by the low soil drainage in TWW irrigated clay soils impairs tree water uptake, which further hinders the soil oxygen levels. Based on these results management tools are suggested to allow sustainable irrigation with TWW in the future. Furthermore, the work demonstrates how analysis of parameters describing the oxygen hourly changes can be utilized to gain mechanistic insights unto processes affecting the oxygen regime in the soil.

Nutritional status, yield components, and yield of cassava as influenced by phenological stages and water regimes

Water deficiency affects several important processes for the plants and, although cassava crop is known to have genotypes well adapted to drought, studies about the characteristics that may indicate tolerance or sensitivity to this abiotic stress are scarce for this crop. The objective of this research was to evaluate the nutritional responses and productive components in cassava plants, in different development stages and under different soil water tensions. The experiment was laid out following completely randomized design, composed by three growth stages, 90 to 180, 180 to 270 and 270 to 360 days after planting (DAP), and three soil water tensions (−10, −40 and − 70 kPa), with five replicates. The plants were mainly affected from 90 to 180 DAP, by soil tensions (−40 and −70 kPa), showing decreases in K and Fe levels and increases in P, Mg and Zn levels. The yield components were also affected by water deficit in this stage, with decreases in the shoot dry matter mass (61.7%), of the tuberous roots (80.4%) and of the stake (43.9%). The imposition of severe water deficit caused 100% of reduction in the diameter and length of the commercial root, in the peel thickness and in the pulp diameter. And yield was drastically affected by soil tensions −40 and −70 kPa in the third and fifth growth stages.

Peat depth as a control onSphagnummoisture stress during seasonal drought

AbstractPeatlands are globally important long‐term sinks of carbon, however there is concern that enhanced peat decomposition and moss moisture stress due to climate change mediated drought will reduce moss productivity making these ecosystems vulnerable to carbon loss and associated long‐term degradation. Peatlands are resilient to summer drought moss stress because of negative ecohydrological feedbacks that generally maintain a wet peat surface, but where feedbacks may be contingent on peat depth. We tested this ‘survival of the deepest’ hypothesis by examining water table (WT) position, near‐surface moisture content, and soil water tension in peatlands that differ in size, peat depth, and catchment area during a summer drought. All shallow sites (<40 cm depth) lost their WT (i.e., the groundwater well was dry) for considerable time during the drought period. Near‐surface soil water tension increased dramatically at shallow sites following WT loss, increasing ~5–7.5× greater at shallow sites compared to deep sites (≥40 cm depth). During a mid‐summer drought intensive field survey, we found that 60–67% of plots at shallow sites exceeded a 100 mb tension threshold used to infer moss water stress. Unlike the shallow sites, tension typically did not exceed this 100 mb threshold at the deep sites. Using species dependent water content – chlorophyll fluorescence thresholds and relations between volumetric water content and WT depth, Monte Carlo simulations suggest that moss had nearly twice the likelihood of being stressed at shallow sites (0.38 ± 0.24) compared to deep sites (0.22 ± 0.18). This study provides evidence that mosses in shallow peatland may be particularly vulnerable to warmer and drier climates in the future, but where species composition may play an important role. We argue that a critical ‘threshold’ peat depth specific for different hydrogeological and hydroclimatic regions can be used to assess what peatlands are especially vulnerable to climate change mediated drought.

Temporal variation and controlling factors of tree water consumption in the thornbush savanna

For a typical encroacher tree of the thornbush savanna, we studied the responses of water consumption to changes in soil water availability within 80 cm depth, vapor pressure deficit (VPD), and global radiation. Therefore, we monitored the sap velocities of Senegalia mellifera trees over 2 years in a maximum of 20 stems (6–15 plant individuals) per measurement period on a site in central Namibia. For this water-restricted ecosystem we aimed to understand the role of an encroacher tree on soil water dynamics and potential groundwater recharge.At the day-to-day scale, soil water was the primary driver of cumulative daily sap velocities (Qn-day). In the dry season, Qn-day decreased with increasing soil drought. Rainy seasons triggered multiple sapflow phases, initiated by soil-wetting rain events and associated with increase of soil water. Maximum attainable Qn-day increased with VPD and radiation. We hypothesize a 3-stage response of tree water use to soil water tension (SWT): (1) SWT < pF 2.6–2.7: soil water is optimal for transpiration; (2) pF 2.6–2.7 < SWT < pF 3.2–3.7: transpiration decreases with soil drought; (3) SWT > pF 3.2–3.7: trees minimize transpiration. Our findings contribute to the understanding of tree–grass coexistence in savannas. The responses of tree water use to soil water within 80 cm depth indicate that S. mellifera exploits the same depths as grasses, in contrast to the classic hypothesis of vertical niche differentiation.

Influence of the soil water retention curve type and magnetic water treatment on lettuce irrigation management responses

Abstract This study aimed to evaluate the influence of magnetized water use on lettuce irrigation management responses, and based on the generated data, to evaluate by simulation the influence of soil water retention curve type on the lettuce irrigation management responses. This work was divided into three stages: 1 – determination of field and laboratory soil water retention curves; 2 – lettuce crop irrigation management experiment using soil water retention curve with field data, evaluating different soil water tensions to start irrigation and different water types (magnetically treated water, and non-treated water); and 3 – estimation of the irrigation management responses (simulation) using the soil water retention curve performed in the laboratory (using non-treated water), compared with the experimental results (stage 2). The use of magnetically treated water determined the soil moisture maintenance for a longer time and fewer irrigation events, leading to less water being applied and electricity consumption. The use of the soil water retention curve derived from the field data determined less water and electric energy consumption in Lucy Brown lettuce irrigation, in comparison with the simulated use of the soil water retention curve from laboratory data.

Effect of water regime and harvest stage on essential oil accumulation in basil plant growing in sandy soil

Basil (Ocimum basilicum.L) is an aromatic herb with economic importance due to its essential oils useful for the production of foods, perfumes, and medicines. Its chemical composition may vary by genetic factors, harvesting stage, and water availability. This work evaluated the content, yield, and the composition of sweet basil essential oil irrigated at different levels of soil water tension and harvested at different flowering stages. Plants were grown in 14-L pots inside a greenhouse located at the Sao Paulo State University (UNESP), Brazil. The 15 treatments were the combination of 5 levels of soil water tension that define when to irrigate (20, 30, 40, 50, and 60 kPa) with 3 harvest stages (beginning of flowering, full flowering, and end of flowering). Growth traits including total dry and fresh mass per plant and inflorescences, plant height, stem diameter, and inflorescences number were highest in plants grown at lower soil water tensions, 20 and 30 kPa. The harvesting at the end of flowering generated the highest values of essential oil content and yield. The 60 kPa soil water tension showed the highest percentage of essential oil content in dry mass, indicating that water stress concentrated essential oil in the plant. However, the basil profit is a function of the essential oil yield. The highest essential oil yield (g, dry weight basis) occurred when irrigation started at 20 and 30 kPa. The chemical components of the essential oil showed low variation, regardless of the treatment. For all the treatments, linalool was the components found in a more considerable amount, and its highest accumulation occurred when irrigated at soil water tension of 20 kPa and 30 kPa. A useful recommendation for basil growers is irrigation scheduling with 30 kPa and harvest at the end of flowering.

Development and Nutrient Uptake by Physalis under Different Soil Water Tensions

ABSTRACT The water deficit generated by inadequate management of irrigation can affect the development and yield of crops. However, little is known about irrigation and irrigation management for physalis (Physalis peruviana L.). The objective of this work was to study different soil water tensions as an indicative for irrigation management in physalis crop and to evaluate its effects on crop development and yield, nutrient uptake, and soil chemical attributes. The experiment was conducted in field condition, soil Typic Quartzipsamment. A randomized block design with four soil water tensions (10, 20, 30, and 40 kPa) was used with four blocks and two replications of treatments per block. In order to monitor the soil water tensions, tensiometers were installed at a depth of 0.20 m. Increased soil water tension led to reduced growth and fruit productivity of physalis. Leaf concentrations of nitrogen (N) and potassium (K) increased, calcium (Ca), magnesium (Mg), sulfur (S), boron (B), iron (Fe), manganese (Mn) and zinc (Zn) reduced, and phosphorus (P) and copper (Cu), were not influenced by increased soil water tension. Values of soil pH, P, K, Ca and Mg and base saturation increased, while exchangeable aluminum (Al) and Al saturation decreased with increases in soil water tensions. The highest development and nutrient uptake of the physalis crop were under soil water tension of 10 kPa at 0.20 m deep. It was concluded that, for the evaluated soil, the irrigation management recommended for conducting the physalis crop is with the soil moisture close to the field capacity.

Tree resin as a cultivation strategy under water deficit

ABSTRACT The search for alternatives that enable the improvement of the soil water retention capacity should focus on a better water use by cultivated plants. This study aimed to evaluate the effect of natural tree resin rates and irrigation levels on the cotton (intermediate cycle) and wild radish (short cycle) crops. Two experiments were conducted in a completely randomized design, in a 5 × 5 factorial arrangement, with three replications and five tree resin rates (0, 0.67, 1.33, 2.00 and 2.67 g plant-1), five soil water tensions (15, 30, 45, 60 and 75 kPa) for cotton plants and five irrigation water levels (40, 60, 80, 100 and 120 % of the ETc) for wild radish plants. The plant height, stem diameter and number of leaves were evaluated at 93 days after sowing (DAS) for the cotton plants; while the plant height, root diameter and number of leaves were evaluated at 30 DAS for the wild radish plants, as well as quantified the shoot and root dry weights of both plant species. The application of tree resin reduces the susceptibility of the crop to water deficit, being 2.7 g plant-1 the highest recommended rate to improve the plant development. The use of tree resin increases the water-use efficiency in cotton and wild radish crops in up to 0.68 g L-1 and 69.6 g L-1, respectively.