Essential nutrients’ availability in pecan orchards affected by salinity in southern New Mexico and western Texas

Pecans [ Carya illinoinensis (Wangenh.) K. Koch] are a significant cash crop in the southwest of the United States, and soil properties, irrigation quality, and nutrient availability influence their production. This study was conducted in six orchards along the Rio Grande River in southern New Mexico and southwest Texas during the 2015 and 2016 growing seasons. The objective was to assess the effects of soil texture, irrigation with brackish groundwater, and nitrogen dynamics on pecan kernel percentage (KP), nut length (NL), and nut number per 1 kg (NP). Soil samples were collected from 0‐ to 120‐cm depth and analyzed for electrical conductivity (EC), nitrate (NO 3 − ), total Kjeldahl nitrogen (TKN), and ammonium (NH 4 + ) in February, June, and October. Results showed that NO 3 − concentrations peaked at 286 mg/kg in October 2016 at 20‐ to 40‐cm depth in Fabens 1 orchard, while TKN varied widely, with the highest value (1067 mg/kg) in Fabens 2 orchard at 0‐ to 20‐cm depth. Anthony orchard, with loamy soil and an EC of 5 dS/m, had the longest NL (41.34 mm), the lowest NP (146), and the lowest KP (53.16%). In contrast, Canutillo orchard, with clay loam soil and an EC of 4 dS/m, had the highest KP (57.66%) but shorter NL (27.94 mm). Orchards in sandy loam soils with lower EC showed higher nut production, while loamy soils with higher EC promoted longer nuts. These findings underscore the need for site‐specific nitrogen and salinity management strategies to optimize pecan yield and quality.

Irrigation with RO concentrate and brackish groundwater impacts pecan tree growth and physiology

A compost program was developed on-farm, utilizing tree trimming biomass from a commercial pecan farm comprised of 14-year-old improved cultivar Western Schley pecan (Carya illinoinensis) tree stands. The direct soil application of shredded pecan tree biomass (P) and dairy manure (M) served as a standard on-farm practice. Three composts were produced using P and M with varying levels of other inputs and processing. The PM compost contained only P and M and its production included only weekly turning and watering. The other two composts included P, M, unfinished compost, and clay inputs, and either additional landscaping residues (A) (designated PM/A compost) or “green chop” (on-farm grown legumes, G) (designated PMG/A compost); production of PM/A and PMG/A composts included additional processing steps intended to improve compost quality per the recommendations of a compost consulting company. Soil samples were taken at three depths (0–15 cm, 15–30 cm, 30–61 cm) in November 2017 from the 1.3 ha study plot of trees. The standard practice and compost treatments were applied at approximately 18 t/ha in January 2018 and 2019 at a 15 cm depth. Soils were re-sampled at the end of the two-year study. Composts and soils were analyzed for: pH, sodium adsorption ratio (SAR), electrical conductivity, and total carbon, organic matter, magnesium, calcium, sodium, nitrate-N, total Kjeldahl nitrogen (TKN), available phosphorus, potassium, zinc, manganese, iron, and copper contents. Pecan tree leaf nutrient content, stem water potential, and leaf greenness were also measured one and two years after soil amendment application. While increases in several soil properties were observed with the treatments, only available phosphorus content was significantly different between pre and post at all depths. Electrical conductivity, TKN, Fe, Cu, SAR, and Na content showed significant differences in the upper soil layers. No differences in leaf properties were observed. This suggests that there are minimal differences in the outcomes for compost application compared to in-situ biomass application; additional compost inputs and processing did not provide additional short-term soil or plant benefits for pecan tree production. More work is needed to determine if there are long-term benefits to soil quality, plant health and performance, or carbon sequestration that impact the economic and environmental decision-making processes for composting and application of local organic wastes.

In semi-arid to arid regions, both anthropogenic sources (urban and agriculture) and deeper Critical Zone (groundwater with long flow paths and water residence times) may play an important role in controlling chemical exports to rivers. Here, we combined two anthropogenic isotope tracers: uranium isotope ratios (234U/238U) and boron isotope ratios (δ11B), with the 87Sr/86Sr ratios to identify and quantify multiple solute (salinity) sources in the Rio Grande river in southern New Mexico and western Texas. The Rio Grande river is a major source of freshwater for irrigation and municipal uses in southwestern United States. There has been a large disagreement about the dominant salinity sources to the Rio Grande and particularly significant sources are of anthropogenic (agriculture practices and shallow groundwater flows, groundwater pumping, and urban developments) and/or geological (natural groundwater upwelling) origins. Between 2014 and 2016, we collected monthly river samples at 15 locations along a 200-km stretch of the Rio Grande river from Elephant Butte Reservoir, New Mexico to El Paso, Texas, as well as water samples from agricultural canals and drains, urban effluents and drains, and groundwater wells. Our study shows that due to the presence of localized and multiple salinity inputs, total dissolved solids (TDS) and isotope ratios of U, B, and Sr in the Rio Grande river show high spatial and temporal variability. Several agricultural, urban, and geological sources of salinity in the Rio Grande watershed have characteristic and distinguishable U, Sr, and B isotope signatures. However, due to the common issue of overlapping signatures as identified by previous tracer studies (such as δ18O, δD, δ34S), no single isotope tracer of U, Sr, or B isotopes was powerful enough to distinguish multiple salinity sources. Here, combining the multiple U, Sr, and B isotope and elemental signatures, we applied a multi-tracer mass balance approach to quantify the relative contributions of water mass from the identified various salinity end members along the 200-km stretch of the Rio Grande during different river flow seasons. Our results show that during irrigation (high river flow) seasons, the Rio Grande had uniform chemical and isotopic compositions, similar to the Elephant Butte reservoir where water is stored and well-mixed, reflecting the dominant contribution from shallow Critical Zone in headwater regions in temperate southern Colorado and northern New Mexico. In non-irrigation (low flow) seasons when the river water is stored at Elephant Butte reservoir, the Rio Grande river at many downstream locations showed heterogeneous chemical and isotopic compositions, reflecting variable inputs from upwelling of groundwater (deeper CZ), displacement of shallow groundwater, agricultural return flows, and urban effluents. Our study highlights the needs of using multi-tracer approach to investigate multiple solutes and salinity sources in rivers with complex geology and human impacts.

The productivity, in terms of ability to reproduce, of the earthworm Eudrilius eugeniae (Kinberg), was studied in the laboratory under three (sandy, loamy and clayey) soil conditions with and without cow dung enrichment, in order to determine their individual suitability for the culture and breeding of the species. Ten earthworms of equal sizes were each introduced into two groups of twelve pots, each subdivided into three groups of four pots each, containing 9500g of ordinary sandy, loamy or clayey soils (served as control), and 300g cow dung enriched sandy, loamy and clayey soils (served as experimental). Experimental and control pots were moistened with 750cm3 of water every three days for ten weeks. Both sets of pots were assessed for total earthworm population, their weights and lengths. Percentage increases in earthworm population in the control soil media were 72.5%, 92.5% and 170% in clayey, sandy and loamy soils respectively. Experimental pots yielded 560%, 1700% and 3395% increments in earthworm population for clayey, sandy and loamy soils respectively. Population increments amongst the three soil media differed significantly (P<0.05). Nutrient enriched soils produced significantly higher earthworm population than ordinary soils (P<0.05). The study shows superiority of loamy and nutrient enhanced soil in enhancing earthworm productivity.

Relationship between plant water stress and soil water depletion (SWD) is not investigated thoroughly for irrigated pecans of southern New Mexico. In this study, transient soil water contents, rootzone SWD, and midday stem water potential (SWP) were monitored in mature pecan orchards in sandy loam (Site 1) and silty clay loam (Site 2) soils near Las Cruces, New Mexico. Corresponding to transient variations of soil water content at different depths, daily SWD varied with soil depth but not spatially. The SWD within the rootzone (0–80 cm) was higher in the shallow depths (0–40 cm) where root length density (RLD) was also higher than in the deeper depths (40–80 cm). The SWD at Site 1 was higher compared to Site 2 due to the higher clay content of the latter. The SWD patterns at outside the tree driplines were similar to those under-canopy locations because of similar RLD at the shallow depths. At both pecan orchards, differences in SWP at 2.5, 4.5, and 7.6 m tree heights were evident particularly 10–14 days after irrigation. This was due to the stress caused by decreasing soil water contents at different depths, which were generally significantly correlated with SWP. Midday air temperature was as useful as midday atmospheric vapor pressure deficit for interpreting SWP. Combined influence of soil water content (0–40 cm) and air temperature on midday SWP was significant at both orchards, which can be used as an adjunct for the clear interpretation of SWP to help refine irrigation scheduling.

Soil quality changes due to flood irrigation in agricultural fields along the Rio Grande in western Texas

Soil salinization is a major restricting factor for crop growth and agriculture productivity in coastal areas. Exploring the evolution of soil salinization indicators and physicochemical properties and their relationships in a long-term scale can provide a basis for the restoration, utilization, and prediction of coastal salinized soil. This study aimed to investigate the impact of reclamation years on soil salinization indicators and physicochemical properties in reclaimed coastal tidal land, and analysis the linkage between soil salinization indicators and physicochemical properties after long-term reclamation. Soil sample sites were respectively collected from reclamation regions reclaimed in 1951, 1974, 1982, and 2007 according to typical land use types. Besides, the natural tidal flat was collected as control. Soil samples were divided into two parts to determine soil bulk density (BD), soil water content (SWC), soil particle size distribution (PSD), soil salt content (SSC), pH, sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), cation exchange capacity (CEC), total nitrogen (TN), total phosphorus (TP), organic matter (SOM), alkaline hydrolyzed nitrogen (AN), and available phosphorus (AP). One-way analysis of variations (ANOVA) was conducted to investigate the differences in soil properties within different reclamation years. The linkage between soil salinization indicators and soil physicochemical properties was analyzed by redundancy analysis and Monte Carlo permutation. Compared with uncultivated tidal land, soil salinization indicators (SSC, pH, SAR, and ESP) significantly decreased after 30 years reclamation owing to the natural leaching and field management. Soil nutrients (SOM, TN, TP, AN, AP, CEC) apparently increased after reclamation of 30 years due to long-term fertilization. Moreover, SWC, BD, and SAND gradually decreased, whereas SILT and CLAY gradually increased after reclamation of 61 years. Soil salinization indicators were observed have a positive correlation with SAND and a negative correlation with SILT, CLAY, and soil nutrients. Long-term reclamation could radically decreased soil salinization (SSC, pH, SAR, ESP) and apparently promoted soil nutrients accumulation (SOM, TN, TP, AN, AP, CEC). Furthermore, soil salinization indicators are closely related to soil physicochemical properties, and soil PSD and soil nutrients were considered as the key factors for the differences of soil salinization.

通过硝化抑制剂抑制土壤硝化作用是实现作物铵硝混合营养和提高氮肥利用率的重要途径之一。本试验采用室内模拟的方法, 在人工气候室(25 ℃)黑暗培养条件下, 应用新疆石灰性土壤研究了不同剂量的双氰胺(dicyandiamide, DCD)在砂土、壤土、黏土3 种不同质地土壤中对土壤硝态氮、铵态氮转化的影响及DCD 的剂量效应和硝化抑制效果。处理30 d 内, 各剂量DCD 处理对砂土的硝化抑制率为96.5%~99.4%(平均值为98.3%), 在黏土上为66.9%~85.6%(平均值为77.6%), 在壤土上为49.3%~79.4%(平均值为67.7%), 总体硝化抑制率表现为砂土>黏土>壤土。在砂土上DCD 的剂量效应不明显, DCD 用量从纯氮的1.0%增加到7.0%时, 土壤中硝态氮含量仅增加1.9~10.7 mg·kg^-1(培养30 d 时); 而在壤土和黏土中, 土壤硝态氮含量随DCD 浓度的增加而显著下降, 存在明显剂量效应。这说明施用DCD 可显著抑制新疆石灰性土壤的硝化作用过程, 在砂土、壤土、黏土中DCD 的最佳浓度分别为纯氮用量的6.0%、7.0%和7.0%, 并在培养30 d 内发挥显著作用。

Continuous application of direct sowing: Traffic effect on subsoil compaction and maize (Zea mays L.) yields in Argentinean Pampas

Calocybe indica (milky mushroom), an edible mushroom with significant nutritional value, shows potential for cultivation in subtropical regions. Investigating the composition and diversity of the microbial community structure of the casing materials of C. indica is of great significance for understanding the stable yield of the mushroom. This study evaluated four casing materials—loamy soil (LS), loamy soil + cow dung (LS + CD), loamy soil + sand (LS + S), and plant ash (PA)—for their effects on mushroom yield, soil physicochemical properties, and microbial dynamics. The results demonstrated that LS + CD significantly enhanced the yield (2078.50 g) and fruiting body quality, with the shortest pinhead formation time (7.67 days) and superior morphological traits (e.g., cap diameter: 10.10 cm). Physicochemical analysis revealed LS + CD’s elevated moisture retention (19.7%), nutrient availability (e.g., available P: 59.63 mg/kg), and microbial biomass (C: 399.22 mg/kg), alongside a distinct microbial community dominated by Basidiomycota and Actinobacteria. Conversely, LS + S exhibited poor performance due to low water retention and nutrient deficiencies. Redundancy analysis highlighted strong correlations between soil nutrients (nitrogen, potassium, phosphorus) and microbial composition, with LS + CD fostering a microbiome conducive to mushroom growth. These findings underscore LS + CD as the optimal casing material for C. indica cultivation, improving both yield and soil health. Future studies should explore the functional roles of key microbes and refine organic amendments for sustainable practices.

The use of brackish groundwater (BGW) to supplement irrigation shortfalls has increased because of decreasing surface water availability in the arid areas of the southern United States. Reuse of reverse osmosis (RO) concentrate, a by‐product resulting from desalination of BGW, can increase irrigation portfolio. This 2‐yr greenhouse study aimed to quantify changes in physical and thermal soil properties, and evapotranspiration (ET) rate of pecan [ Carya illinoinensis (Wangenh.) K. Koch] irrigated with BGW and RO concentrate. Another objective was to predict soil thermal conductivity ( K ) using soil electrical conductivity (EC) and soil volumetric water content (VWC) data of 2017–2018. Three irrigation water treatments with four replications were prepared namely, control (EC = 0.8 dS m −1 ), BGW (EC = 4.0 dS m −1 ), and RO concentrate (EC = 8.0 dS m −1 ). Soil physical properties determined were texture, moisture content, bulk density, hydraulic conductivity, and moisture retention. Thermal properties measured were conductivity ( K ), diffusivity ( D ), resistivity (ρ), and heat capacity ( C ). The ET and leaching fractions (LF) were determined using water balance. Pecan irrigated with RO concentrate had the lowest ET among irrigation treatments. Soil thermal conductivities and soil water contents in BGW and RO irrigated pots were higher than the control. However, increases in heat capacity with increasing irrigation water salinity were most pronounced. The new four parameters‐based model using EC and VWC explained 96% of variability of K (average R 2 = .96, RMSE = 0.096, normalized RMSE [NRMSE] = 11.14%). The sensitivity analysis showed that the contribution of VWC to K was greater than that of EC. Results indicate that continuous irrigation with RO concentrate can be done for up to 1 yr. A new irrigation scheduling protocol based on optimal LF and soil salinity is needed to sustain pecan production in southern New Mexico.

Potassium (K) deficiency is a major constraint to crop productivity in Egyptian soils, particularly in coarse-textured soils. In pot experiments, the study evaluated impact of application of biochars at a rate of 3% (w/w) produced at 450 °C for 4 h, from four agricultural residues (sugarcane bagasse residues biochar (SBR), olive stone pomace biochar (OSP), orange fruit pomace biochar (OFP), and maize stover residues biochar (MSR)) on K availability, K dynamics, and specific soil physicochemical properties across four Egyptian soil types (sandy, loamy, clayey, and calcareous), in addition to its effects on wheat growth. Biochars varied in surface area (23.72–41.82 m² g⁻¹) and nutrient content, with MSR showing the highest plant available nutrients, while OSP exhibited the highest cation exchange capacity (56.78 cmol (+) kg⁻¹). Application of biochars increased soil water-holding capacity (WHC) by 17–35.5%, cation exchange capacity (CEC) by 18–163%, depending on soil type. Thermodynamic parameters of K were significantly improved; labile-K (KL) increased by 103.6% in sandy soil with MSR, 59.01% in loamy soil with OSP, 48.55% in clayey soil with SBR, 849% in calcareous soil with MSR. Activity ratio of K at equilibrium (:{mathrm{AR}}_{0}^{mathrm{K}}) increased by 33.33% in sandy soil with MSR, 20.00% in clayey soil with SBR, 75.0% in calcareous soil with MSR, while in loamy soil decreased by − 16.66% in loamy soil with OSP. Potential buffering capacity of K (PBCK) increased with application of MSR by 96.99%, 119.89%, 45.90% in sandy, loamy and clayey soils, while PBCK increased by 421.39% with OSP application in calcareous soil. Gibbs free energy (ΔG) became more negative (up to − 5.565 kcal mol⁻¹), and Gabon selectivity coefficient (KG) increased by 82.5%. Wheat fresh and dry biomass increased by 25.9–84.6% and 16.9–63.8%, respectively. Uptake of N, P, and K on wheat tissues increased by 27.3–142.2%, depending on biochar type and soil. In general, biochar-amended treatments produced higher wheat biomass and nutrient uptake than the unamended controls, with MSR demonstrating the most consistent performance across different soil types, followed by OSP. These findings highlight the importance of matching biochar type with soil characteristics to optimize K availability, improve K-use efficiency, reduce reliance on mineral fertilizers, and support sustainable soil fertility management under arid and semi-arid conditions.

Biochar application can alleviate the adverse effects of saline-alkali stress on crops. However, the long-term effects of one-off biochar application on soil physicochemical properties, salt concentration, nutrient availability, soil enzyme activities, and rice yield under highly saline-alkali paddy soils remain unclear. Here, a 6-year paddy field study was conducted in a saline-alkali paddy field using two nitrogen application levels (0 and 225 kg ha−1) and four biochar application rates [0 (T0), 1.5% (T1.5), 3.0% (T3.0), and 4.5% (T4.5) biochar, w/w]. The results showed that compared with T0, the bulk density (BD) under T1.5, T3.0, and T4.5 treatments significantly decreased by 11.21%, 16.33%, and 25.57%, while total porosity (Tp) and saturated hydraulic conductivity (Ks) increased by 19.15–27.34% and 3217.78–5539.83%, respectively. Biochar consistently improved soil macro-aggregates, mean weight diameter (MWD), and the percentage of water-stable aggregates (PWSA) over the years. Additionally, one-off application of biochar continuously reduced the soil Na+ concentration, Na+/K+ ratio, Na+/Ca2+ ratio, saturated paste extract (ECe), exchangeable sodium percentage (ESP), and sodium adsorption ratio (SARe). However, it reduced the pH in 2021 and 2022 only. It enhanced the concentration of K+, Ca2+, Mg2+, and cation exchange capacity (CEC) over the 6-year study, indicating its longer-term positive impact. Furthermore, the one-off biochar application, especially under high application rate treatments (T3.0 and T4.5), significantly and continuously improved nutrient availability and soil enzyme activities. However, alkali-hydrolysable nitrogen (AN) decreased in the initial year of biochar application. The grain yield of T1.5, T3.0, and T4.5 surpassed that of T0 by 116.38%, 141.24%, and 145.20%, respectively. Notably, the rice yield reached its peak with the treatment of 3.0% (w/w) in all 6 years of study period. These findings offered new perspectives on repairing and improving soil quality and production ability of highly saline-alkali paddy soils.Graphical

Fecal samples were taken from wild ducks on the lower Rio Grande River around Las Cruces, N. Mex., from September 2000 to January 2001. Giardia cysts and Cryptosporidium oocysts were purified from 69 samples by sucrose enrichment followed by cesium chloride (CsCl) gradient centrifugation and were viewed via fluorescent-antibody (FA) staining. For some samples, recovered cysts and oocysts were further screened via PCR to determine the presence of Giardia lamblia and Crytosporidium parvum. The results of this study indicate that 49% of the ducks were carriers of Cryptosporidium, and the Cryptosporidium oocyst concentrations ranged from 0 to 2,182 oocysts per g of feces (mean +/- standard deviation, 47.53 +/- 270.3 oocysts per g); also, 28% of the ducks were positive for Giardia, and the Giardia cyst concentrations ranged from 0 to 29,293 cysts per g of feces (mean +/- standard deviation, 436 +/- 3,525.4 cysts per g). Of the 69 samples, only 14 had (oo)cyst concentrations that were above the PCR detection limit. Samples did test positive for Cryptosporidium sp. However, C. parvum and G. lamblia were not detected in any of the 14 samples tested by PCR. Ducks on their southern migration through southern New Mexico were positive for Cryptosporidium and Giardia as determined by FA staining, but C. parvum and G. lamblia were not detected.