Irrigated Sandy Soils Research Articles

Response of dark red kidney beans to nitrogen on irrigated, sandy soil

AbstractThere is a lack of nitrogen response research on dark red kidney beans (Phaseolus vulgaris L.). This is of particular importance as most cultivars form nodules and are commonly grown on sandy soil. The objectives of this study were to determine the effects of nitrogen rates and irrigation amounts on leaf area index, white mold occurrence, yield, and N uptake of dark red kidney beans. The study occurred at the University of Wisconsin Hancock Agricultural Research Station over two growing seasons (2020 and 2021), across four N rates, three irrigation levels, and five cultivars. Preceding crop for each study year was potato and field corn, respectively. More heavy rainfall events that may lead to leaching were observed in 2021. Neither irrigation effect nor general cultivar difference was observed on bean yield, disease resistance, and nitrogen use across the 2 years. Bean yield was significantly influenced by N rates across the five cultivars in 2020 but not in 2021, with 56 kg ha−1 more total N uptake at the lowest N rate in 2021. This highlights large site‐year influences on N supply from fixation. Furthermore, although greater N application did lead to greater yield in 1 year, it was also associated with greater white mold disease pressure and lower partial factor productivity (PFP). Thus, there is economic risk in N application to dark red kidney beans on irrigated sandy soil from reduced quality (mold damage) and lower N use efficiency (indicated by lower PFP), although site‐year effects remain unknown.

Changes in the morphological structure and mechanical properties of sandy soils

The analysis of the genesis, properties of sand and sandy soils developed in different periods in Central Fergana, the changes in the agro-ecological and reclamation conditions under the influence of anthropogenic factors involves in the efficient use of land resources. The main purpose of the study is to study the genesis, geography, and formation of soils formed in sandy areas, eco-reclamation processes occurring under the influence of natural conditions and irrigation, to determine the agrochemical, physicochemical and other properties of irrigated sandy soils. The research was carried out in the field, laboratory, and cameral conditions according to generally accepted standard methods in soil science, the research used geographical, morphological, natural-historical, chemical-analytical, and cross-sectional methods. The scientific significance of the results of the study is explained by the laws of specific formation and distribution of sandy soils and irrigated sandy soils of Central Fergana, changes in the eco-reclamation state under the influence of anthropogenic factors, disclosure of physical and mechanical dynamics, productivity, conservation, and restoration.

Effect of Zinc Nanoparticles on Plant Growth and Some Soil Properties

A field experiment with three replications was conducted on sprinkler irrigated sandy soil during two successive summer and winter seasons (summer 2021 and winter 2021/2022), which cultivated with corn (Zea mays) and faba bean (Vicia faba L.) at Agricultural Research Station farm in Ismailia Governorate, Egypt. Faba bean (Vicia faba L.) was cultivated as an indicator crop to evaluate the residual effect of different rates of zinc nutrient in nanoparticles form versus mineral zinc sulphate fertilizer and studying their effects on growth and crop yield and some soil chemical properties. The zinc nutrient forms were applied by fertigation through sprinkler irrigation system. The obtained results revealed that the corn and bean parts dry matter, yield and some soil chemical properties including available soil nutrients content, EC, pH and SOM were greatly improved in general with additions of these nutrients forms. During zinc nanoparticles treatments, the most effective treatment was with the rate of half dose from minerals at recommended dose (ZnNPs at 50% MNRD). Mineral forms in normal recommended dose (MNRD) gave nearly equal effect with ZnNPs at 50 % MNRD.

Properties of Humic Acids in Meadow Soils Irrigated with the Slope-and-Flooding System

The still-advancing soil degradation and the related losses of soil organic carbon stocks due to the limited inflow of organic residues in agro-ecosystems encourage more and more soil protection. Establishing meadow ecosystems is one of the key methods of agricultural land use preventing losses of organic carbon in soils. Based on the research on the properties of humic acids, it is possible to determine the advancement of the processes of transformation and decomposition of soil organic matter. The obtained results may allow for the development of a soil protection strategy and more effective sequestration of organic carbon. Therefore, the aim of the research was to determine the properties of humic acids defining the quality of organic matter of meadow soils irrigated for 150 years with the slope-and-flooding system. The research was performed based on the soils (Albic Brunic Arenosol) sampled from Europe’s unique complex of permanent irrigated grasslands (the same irrigation management for 150 years), applying the slope-and-flooding system: the Czerskie Meadows. The soil samples were assayed for the content of total organic carbon (TOC) and the particle size distribution. HAs were extracted with the Schnitzer method and analysed for the elemental composition, spectrometric parameters in the UV-VIS (ultraviolet-visible) range, hydrophilic and hydrophobic properties and the infrared spectra. The research results showed that the HAs properties depend on the depth and the distance from the irrigation ditch. The HAs of soils sampled from the depth of 0–10 cm were identified with a lower “degree of maturity” as compared with the HAs of soils sampled from the depth of 20–30 cm, reflected by the values of atomic ratios (H/C, O/C, O/H), absorbance coefficients, and the FT-IR (Fourier transform infrared) spectra. The mean values of the H/C ratio in the HAs molecules of soils sampled from the depth of 20–30 cm were lower by 8.2% than those from the depth of 0–10 cm. The mean values of the absorbance coefficient A4/6 in the HAs molecules of soils sampled from the depth of 20–30 cm were lower by 9.6% than in the HAs molecules of soils sampled from the depth of 0–10 cm. The HAs molecules of the soils sampled 25 m from the irrigation ditch were identified with a higher degree of humification, as compared with the HAs of the soils sampled 5 m from the irrigation ditch. The results identified that humic acids produced in the many-year irrigated sandy soils were identified with a high degree of humification, which proves the relative stability of the soil’s organic matter. It confirms the importance of meadow soils for the carbon sequestration process. It should also be emphasized that the research area is interesting, although hardly described in terms of organic matter properties. Further and more detailed applicable research is planned, e.g., monitoring of total organic carbon content and comparing the properties of irrigated and non-irrigated meadow soils. Continuity of research is necessary to assess the direction of the soil organic matter transformation in such a unique ecosystem. The obtained results may allow for the development of, inter alia, models of agricultural practices that increase carbon sequestration in soils. In the long term, this will allow for greater environmental benefits and, thus, also increased financial benefits.

Split application of stabilized ammonium nitrate improved potato yield and nitrogen-use efficiency with reduced application rate in tropical sandy soils

Urea is the dominant nitrogen (N) fertilizer used for potato (Solanum tuberosum L.) cultivation in most parts of the world. Fertilizers containing a nitrification inhibitor (NI) claim to improve performance of crops including potato. No studies to date have conducted comprehensive assessment of N sources and the effectiveness of NI under varying N rates or application timings to enhance potato yield, tuber quality or N-use efficiency (NUE) in tropical regions. Three field experiments were conducted on irrigated sandy soils in southeastern Brazil to determine whether single or split application of ammonium sulfate nitrate (ASN) with the NI 3,4-dimethylpyrazole phosphate (DMPP) at reduced (75%) or recommended N rates (RNR, 100% = 160 kg ha-1) could improve yield, quality and/or NUE of ‘Agata’ potato over conventional split-applied urea at 100% of RNR. Compared to the conventional practice, split-applied ASN + DMPP, at either 75% or 100% of RNR, increased fresh tuber yield by an average of 15% across all site-years (SYs) and reduced N surplus in SYs with greater rainfall events suggesting that reactive N losses to the environment were also reduced. With split-applied ASN + DMPP at 75% of RNR, fresh tuber yield per unit of applied N increased by 34% compared to split-applied ASN + DMPP at 100% of RNR, and by 50–75% compared to a single application of ASN + DMPP at planting. These results demonstrate a mutually beneficial opportunity, where the rate of split-applied ASN + DMPP can be reduced by 25% while at the same time increasing yields, thus resulting in agronomic, economic, and environmental benefits due to the decreased potential for off-site reactive N losses.

Nitrogen source and rate effects on residual soil nitrate and overwinter NO3-N losses for irrigated potatoes on sandy soils

Residual soil NO3-N (RSN) is susceptible to loss during the non-growing season. This 5 yr study investigated the effects of three N fertilizer sources [ammonium nitrate (AN), ammonium sulfate (AS), and polymer-coated urea (PCU)] applied at four rates (60, 120, 200, and 280 kg N ha−1) plus an unfertilized control on RSN following potato production and on overwinter NO3-N changes in an irrigated sandy soil in Quebec, Canada. Composite soil samples were collected at the 0–15, 15–30, 30–60, and 60–90 cm depths immediately after potato harvest in fall and again in the following spring from 2008 to 2012. Residual soil NO3-N content within the 0–30 cm depth (RSN0–30) was highly correlated with the RSN content in the 0–90 cm depth (RSN0–90), indicating that RSN0–30 can be used as an indicator of soil profile NO3-N accumulation. Overall, RSN0–90 increased with fertilizer N application rate, particularly for above the minimum fertilizer N rate required to maximize yield (Nmax), and was generally higher for years with greater pre-plant soil NO3-N. The split application of AN and AS resulted in lower RSN0–90 than the single application of PCU at above Nmax. Overwinter losses of soil NO3-N were generally increased with increasing RSN0–90 in fall. The results suggest that reducing the fertilizer N rate is more important than the choice of N source in managing RSN.

Polymer‐coated UREA use for corn on irrigated sandy soil

Improved nitrogen (N) management in corn production is needed to optimize economic returns to farmers and minimize environmental concerns associated with agricultural N use. This study examines the optimum timing and rates of polymer‐coated urea on corn yield and N use efficiency under varying seasonal precipitation on irrigated sandy soils. Earn 0.5 CEUs in Nutrient Management by reading this article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/726.

Assessing the Benefit of Polymer‐Coated Urea for Corn Production on Irrigated Sandy Soils

Core Ideas Polymer‐coated urea led to greater yields compared to other N fertilizers when all applied preplant. The performance of preplant polymer‐coated urea is reduced in high rainfall years. Split application of ammonium sulfate consistently produced the greatest yields on irrigated sands. Nitrification inhibitor showed little impact on corn yield on irrigated sandy soils. Polymer‐coated urea (PCU) is an enhanced‐efficiency fertilizer product that can potentially increase N use efficiency, thereby reducing N losses to the environment. However, the optimum timing and rates of PCU application under varying seasonal precipitation is less known. Here we studied the response of corn (Zea mays L.) yield and N use efficiency to N timing (preplant, sidedress, and split application) and rates (112–280 kg N ha−1) of PCU, ammonium sulfate (AS), and urea, including a control treatment without N, on an irrigated sandy soil (90% sand) in central Wisconsin from 2003 to 2006. The effect of N rate on grain yield was significant in 2003, 2004, and 2005, but not in 2006. Grain yield and N recovery efficiency (RE) with preplant PCU was greater in 2004 and 2005, and similar in 2003 and 2006 compared with preplant AS or urea. Preplant PCU had similar or greater yield and RE compared with split‐applied AS in 3 yr, but lower yield and RE in the year with the greatest early season rainfall. Nitrification inhibitor (dicyandiamide) showed little impact on corn yield. These results indicated that PCU, when applied preplant, was agronomically and environmentally advantageous over the other N fertilizer sources and typically performed as well as split application of other N fertilizers. However, under conditions where there is a lot of early season rainfall, use of preplant PCU would still result in N losses and then crops would need supplemental N to achieve high yields.

Phosphorus requirement for irrigated bush beans production on coastal plain soils

Economic agricultural production of coastal plain sandy soils requires intensive nutrient and irrigation management. Optimization of nitrogen and phosphorus applications will bring environmental sustainability also to the production. A greenhouse study was conducted on irrigated sandy soils with bush beans comparing six different phosphorus (P) rates set in completely randomized blocks with four replications during 2016 and 2017 to determine optimum P requirement. Soil and tissue nutrients, plant height, dry matter, and relative yield (RY) data were collected. Agronomic Use Efficiency (AUE) was calculated. Highest RY and AUE were recorded at 53 or 59 kg ha−1 of P application rates, above which there was no response. A negative P: zinc (Zn) impact was also documented. A maximum soil application rate of 59 kg P ha−1 can be suggested as adequate to optimize the yield of bush beans produced on coastal plain sandy soils of the southeastern United States.

Nitrogen Source and Rate Effects on Irrigated Potato in Tropical Sandy Soils

Core Ideas A suitable nitrogen source and optimum nitrogen rate can improve potato yield and nitrogen‐use efficiency in tropical sandy soils. Regardless of the nitrogen source, the nitrogen fertilization increased the potato tuber yield up to rates between 136 kg nitrogen ha−1 and at least 160 kg nitrogen ha−1. Ammonium sulfate nitrate plus DMPP promoted greater total and marketable tuber yields than urea and higher agronomic efficiency compared to urea and ammonium sulfate. There is a potential for ammonium sulfate nitrate plus DMPP to improve the synchronization between soil nitrogen availability and potato nitrogen demand when potato is cultivated in a tropical sandy soil. A suitable N source and an optimal application rate can improve the N‐use efficiency of potato (Solanum tuberosum L.) while minimizing N losses, especially when potato is grown in sandy soils. Three experiments were conducted at irrigated sandy soil sites in São Paulo State, Brazil, to evaluate the effects of ammonium sulfate (AMS), ammonium sulfate nitrate with the nitrification inhibitor 3,4‐dimethylpyrazole phosphate (ASN+DMPP), and urea applied at three N rates (80, 120, and 160 kg ha−1), as well as a zero‐N control on potato (cv. Agata). Leaf N and S concentrations, tuber yield, and agronomic efficiency (AE) were measured. The 80 kg N ha−1 rate was applied in the furrow at planting, and the other rates were split‐applied, with 40 kg N ha−1 in the furrow at planting and the remainder applied at hilling. Regardless of the N source, the N fertilizer rates increased the potato leaf N concentration and tuber bulking of the potato crop, which in turn increased the tuber yield up to rates between 136 kg N ha−1 and at least 160 kg N ha−1. Among the N sources, ASN+DMPP fertilizer resulted in a higher potato tuber set and yield than urea and led to the highest AE compared to AMS and urea. Overall, these results suggest the potential for ASN+DMPP to improve the synchronization between soil N availability and potato N demand and provide a more appropriate balance of N forms in the soil when potato is cultivated in sandy soils in a tropical climate.

Chemical composition of Mentha pulegium L. (Pennyroyal) plant as influenced by foliar application of different sources of zinc

Background and objective Mentha pulegium L. is commonly known as pennyroyal and it is highly aromatic than any other mint. The essential oil could be considered as a possible candidate for human cancer chemotherapy. This study was carried out to evaluate the effect of different sources of zinc (algae extract, zinc sulfate, zinc multi, and zinc chelated) on herb yield, nutrient contents and their uptake, carbonic anhydrase, and essential oil production of M. pulegium plant. Materials and methods A field experiment was carried out under drip irrigated sandy soil at the Experimental Station of National Research Centre in Nubaria district, El-Behira Governorate, Egypt. Macronutrients and micronutrients contents of herb, nutrient uptake, carbonic anhydrase activity, and essential oil content were determined. Essential oil constituents were analyzed by chromatography-mass spectrometry. Results The results showed that algae extract followed by zinc multi significantly increased herb fresh and dry weight yield, nutrients content and their uptake, as well as showed the stimulatory impact on carboxylation enzyme activities. The highest essential oil yield (0.93 ml/plant and 20.67 l/ha) was recorded with algae extract, followed by zinc multi (0.80 ml/plant and 17.78 l/ha) than zinc chelate (0.50 ml/plant and 11.11 l/ha). Chromatography-mass spectrometry analyses of the essential oil showed that the essential oil composition was characterized by a high percentage of oxygenated compounds (96.83–97.33%) while the nonoxygenated compounds ranged from 2.48 to 2.89%. The major constituents of oxygenated compounds were found to be pulegone (67.75–74.43%) followed by neomenthone (10.66–17.12%). Algae extract and zinc multi produced the highest relative concentration of neomenthone (17.12 and 16.72%) and the lowest concentration of pulegone (67.75 and 67.97%). In contrast, foliar application of zinc chelated and zinc sulfate increased the biosynthesis of pulegone (74.43 and 73.98%) and decreased the percent of neomenthone (11.39 and 10.66%). Conclusion It might be concluded that the foliar application of zinc as algae extract followed by zinc multi chelated gave remarkable higher increases in herb yield, nutrients content and their uptake, carbonic anhydrase and essential oil production of M. pulegium plant.

Various soil amendments and environmental wastes affect the (im)mobilization and phytoavailability of potentially toxic elements in a sewage effluent irrigated sandy soil

Contamination of long-term sewage effluent irrigated soils by potentially toxic elements (PTEs) is a serious concern due to its high environmental and health risk. Our scientific hypothesis is that soil amendments can cause contradictory effects on the element mobilization and phytoavailability depending on the type of element and amendment. Therefore, we aimed to assess the impact of the application (1%) of several low cost amendments and environmental wastes on the (im)mobilization, availability, and uptake of Al, Cd, Cr, Cu, Fe, Mn, Ni, and Zn by sorghum (Sorghum bicolor) in a long term sewage effluent irrigated sandy soils collected from Egypt. The used materials include activated charcoal (AC), potassium humate (KH), phosphate rock (PR), phosphogypsum (PG), triple superphosphate (TSP), phosphoric acid (PA), sulfur (S), sugar beet factory lime (SBFL), cement bypass kiln dust (CBD), egg shell (ES), bone mill (BM), brick factory residual (BFR), ceramic powder (CP), and drinking water treatment residual (WTR). The mobilization and availability of the elements in the soil were extracted using NH4NO3 and ammonium bicarbonate- diethylene triamine penta acetic acid (AB-DTPA), respectively. The above-ground biomass samples were analyzed for the elements studied.The results confirmed our hypothesis and concluded that although some amendments like S, PA, and TSP can be used for reducing the plant uptake of Al, Cr, and Fe, they might be used with KH for enhancing the phytoextraction of Cd, Cu, Mn, and Ni. Moreover, several wastes such as BFR and WTR might be used for enhancing the phytoextraction of Al, Cd, Cr, Cu, Fe, and Ni and reducing the uptake of Mn from the studied soil. Although SBFL decreased the plant uptake of Al, Fe, Mn, and Zn, it's increased the plant uptake of Cd, Cu, and Ni. Therefore, the amendments which reduce the plant uptake of an element might be suitable candidates for its immobilization, while the amendments which increase the plant uptake of an element might be used for enhancing its phytoextraction when using bioenergy crops like sorghum in similar contaminated sandy soils. The studied materials offered the potential for effective and low cost media for the treatment of PTEs contaminated sewage effluent irrigated sandy soils. These results should be verified in a field study.

Nitrogen Management for Corn and Groundwater Quality in Upper Midwest Irrigated Sands.

Groundwater contamination from NO-N leaching in corn ( L.) production with coarse-textured soils poses an environmental concern. Our objectives were to evaluate NO-N leaching in continuous corn (CC), corn after soybean ( L.) (CSb), and soybean after corn (SbC) in irrigated sandy soils in Minnesota related to (i) N rate using best management practices of split-N application, (ii) a split-N application and single preplant applications of enhanced-efficiency fertilizers (EEF), and (iii) residual N treatment in SbC. Urea (0-315 kg N ha in 45-kg increments) was broadcast as a split application (half at preplant and half at the V4 development stage) and polymer-coated urea (ESN), ESN/urea, and SuperU at preplant at a rate of 180 kg N ha on an Arvilla sandy loam soil. In May and June, 75% of the total drainage and 73% of the total NO-N leached occurred. At the economic optimum N rate (EONR), season-long NO-N leaching rates were 86 and 106 kg NO-N ha for CC and CSb, respectively. In CC, reducing the EONR by 20% reduced grain yield by 4% and NO-N leached by 9%, and a 25% reduction in EONR resulted in an additional 2% reduction for both, whereas no significant reductions occurred for CSb. Similar NO-N leaching occurred with EEFs and the split-N application. After 4 yr of no N application, we measured 9 to 20 mg NO-N L and leaching of 21 to 51 kg NO-N ha, highlighting the difficulty of meeting drinking water quality standards in corn cropping systems.

Maize Yield and Nitrogen Use Efficiency in Upper Midwest Irrigated Sandy Soils

Corn (Zea mays L.) in irrigated coarse‐textured soils can be very productive with N applications, but excess N can increase groundwater contamination. Our objectives were to (i) determine the economic optimum nitrogen rate (EONR) for continuous corn (CC) and corn after soybean [Glycine max (L.) Merr.] (CSb), (ii) evaluate corn yield and nitrogen use efficiency (NUE) of split urea‐N and single pre‐plant application of enhanced‐efficiency fertilizers, and (iii) determine the utility of canopy sensors and basal stalk nitrate‐N test to manage N. Rotations of CC in Dakota County, Minnesota, and CC, CSb, and soybean after corn (SbC) in Pope County, Minnesota, were established in 2011 to 2014 with 0, 45, 90, 135, 180, 225, 270, and 315 kg urea‐N ha−1 as split‐application (half at pre‐plant and half at V4), and pre‐plant applications of SuperU (Koch Fertilizer LLC, Wichita, KS) at 180 kg N ha−1, ESN(Agrium Advanced Technologies, Loveland, CO)/urea blend 90/90 kg Nha−1, and ESN at 180 and 225 kg N ha−1. The EONR for CC was 233 kg N ha−1. The fertilizer replacement value in CSb was 56 kg N ha−1 and the EONR was 49 kg N ha−1 less than in CC. Canopy sensors and basal stalk nitrate‐N generally under estimated N rate. A split‐urea application increased corn grain yield by 5.4% (0.63 Mg ha−1), partial factor productivity (PFP) by 6% and agronomic efficiency (AE) by 12% relative to mean single pre‐plant application of enhanced‐efficiency fertilizers. In irrigated sandy soils, applying high rates of N needed for economic optimum yield is best accomplished by splitting the application.Core Ideas In irrigated sandy soils, applying high rates of N needed for economic optimum yield is best accomplished by splitting the application. Canopy sensors and basal stalk nitrate‐N generally under estimated N rate needed to optimize grain yield. Enhanced efficiency fertilizers applied at pre‐plant are not as effective as split applications of urea in irrigated sandy soils.

Potato Response to Nitrogen Sources and Rates in an Irrigated Sandy Soil

Management strategies to reduce N losses to the environment from potato (Solanum tuberosum L.) production while maintaining yields depend on selecting the right N source and rate. A 5‐yr (2008‐2012) field experiment was conducted on an irrigated sandy soil in Quebec, Canada, to examine the effect of N fertilizer source and rate on total (TY) and marketable tuber yield (MY), total plant N accumulation (vines + tubers), specific gravity, culls (unmarketable tubers), and apparent fertilizer N recovery (ANR). The treatments included an unfertilized control, and three N sources [ammonium nitrate (AN), ammonium sulfate (AS), and polymer‐coated urea (PCU)] applied at four rates (60, 120, 200, and 280 kg N ha−1). The PCU was applied 100% at planting and the AN and AS were applied 40% at planting and 60% at hilling. The TY and MY increased with N rate up to 200 kg N ha−1, but were similar among the N sources. On average, total plant N accumulation and ANR were greater for AN and PCU than AS. However in 2008, when there was a greater risk of N loss due to high rainfall, total plant N accumulation and ANR were greater for PCU than AN and AS. Tuber specific gravity and culls were influenced by N rate, but the response was dependent on soil and climatic conditions. Results suggest that, under humid conditions with irrigation, a one‐time application of PCU in potato production can minimize the risk of N loss without reducing tuber yield and quality.

Seasonal monitoring of soil salinity by electromagnetic conductivity in irrigated sandy soils from a Saharan oasis

Monitoring soil salinity over time is a crucial issue in Saharan oases to anticipate salinisation related to insufficient irrigation management. This project tested the ability of electromagnetic conductivity surveys to describe, by means of regression-tree inference models, spatiotemporal changes in soil salinity at different depths within a complex 10-ha pattern of irrigated plots in an Algerian oasis. Soils were sandy Aridic Salic Solonchaks with a fluctuating saline watertable at less than 2 m. Apparent electrical conductivity (ECa) was measured by an EM38 device at fixed 10- or 20-m intervals (2889 points) at four sampling dates between March 2009 and November 2010. For calibration and validation purposes, soil salinity was measured from a 1 : 5 diluted extract (EC1:5) in three layers (0–10, 10–25, 25–50 cm) at 30 of these points randomly chosen at each date. ECa measurements were used to predict EC1:5 using calibration regression trees created with the software Cubist, including either parameters specific to the study site (specific model) or more general parameters (general model), allowing extrapolation to other sites. Performance of regression tree predictions was compared with predictions derived from a multiple linear regression (MLR) model adjusted for each date using the software ESAP. Salinity was better predicted by Cubist regression tree models than MLR models. For the deep layer (25–50 cm), Cubist models were more accurate with the specific model (r2 = 0.8, RMSE = 1.6 dS/m) than the general model (r2 = 0.4, RMSE = 2.5 dS/m). Prediction accuracy of both models decreased from the bottom to the top of the soil profile. Salinity maps showed high inter-plot variability, which was captured better by the more flexible regression-tree inference models than the classic MLR models, but they need to build site-specific prediction models. Overall, the monitoring surveys, combined with the Cubist prediction tool, revealed both the seasonal dynamics and spatial variability of salinity at different depths.

Impact of activated charcoal and tannin amendments on microbial biomass and residues in an irrigated sandy soil under arid subtropical conditions

Effects of goat manure application combined with charcoal and tannins, added as feed additives or mixed directly, on microbial biomass, microbial residues and soil organic matter were tested in a 2-year field trial on a sandy soil under Omani irrigated subtropical conditions. Soil microbial biomass C revealed the fastest response to manure application, followed by microbial residue C, estimated on the basis of fungal glucosamine and bacterial muramic acid, and finally soil organic C (SOC), showing the slowest, but still significant response. At the end of the trial, microbial biomass C reached 220 μg g−1 soil, i.e. contents similar to sandy soils in temperate humid climate, and showed a relatively high contribution of saprotrophic fungi, as indicated by an average ergosterol to microbial biomass C ratio of 0.35 % in the manure treatments. The mean fungal C to bacterial C ratio was 0.55, indicating bacterial dominance of microbial residues. This fraction contributed relatively low concentrations of between 20 and 35 % to SOC. Charcoal added to manure increased the SOC content and the soil C/N ratio, but did not affect any of the soil microbial properties analysed. Tannins added to manure reduce the 0.5 M K2SO4-extractable N to N total ratio compared to manure control. These effects occurred regardless of whether charcoal or tannins were supplied as feed additive or directly mixed to the manure.

Impact of manure and slurry applications on soil nitrate in a maize–triticale rotation: Field study and long term simulation analysis

Estimation of nitrate leaching from agricultural systems is critical to environment impact studies. Simulation models can help to assess and understand the dynamics of nitrates in the soil and in relation to fertilizer types and agronomical management. The main hypothesis of this study was that the long term annual application of mineral and organic N fertilizers, in irrigated sandy soil areas increases dramatically the quantity of NO3− in the soil for potential nitrate leaching. The main objectives of this research were then to quantify inorganic N concentration in soil layers affected by mineral and organic N (manure and slurry) fertilizers; and to test the SALUS crop simulation model to identify the best N management strategy able to minimize NO3− leaching without compromising crop growth and yields. A first set of rotational simulations were carried out for the 2007 and 2008 experiments, with the goal of comparing measured and simulated results. A second set of rotational simulations were carried out for a long term assessment (50years) of the two treatments in comparisons. Additional long term rotational simulation runs were carried out considering two different fertilization strategies based on the maize crop uptake in 2007 (276kgNha−1) and on the PUA (“Best Nitrogen Management with manures”) which defines the fertilization practices adopted in the nitrate vulnerable zones (no more than 170kgNha−1year−1). Measured data showed that in the manure treatment, the highest nitrate-N concentration was 627.3mgkg−1 at 0.10m depth on August 2008, while the lowest was 2.50mgkg−1 at 1.40m depth on July 2007. In the slurry treatment, the maximum nitrate N concentration was 344.6mgkg−1 at 0.10m depth on August 2008 and the minimum was 8.9mgkg−1 at 0.60cm depth on September 2007. The model was able to closely reproduce the measured results. The simulation results of the inorganic soil N were 1228kgha−1 and 1370kgha−1 for the manure and slurry treatment respectively versus the measured soil inorganic N content at the beginning of the experiment of 1267kgha−1 for the manure treatment and 1323kgha−1 for the slurry treatment. The simulated cumulative amount of nitrate leaching was 9251kgha−1 for the manure treatment and 11,101kgha−1 for the slurry treatment for the 50years simulations.The simulations results also showed that when the inorganic N was used alone, the amount of leaching and soil N were significantly reduced.

Potato Response to Nitrogen Form and Nitrification Inhibitors

Several previous experiments where nitrification inhibitors have been used with potato have resulted in yield and/or tuber quality reductions, especially when used in combination with all-ammonium fertilizer N sources. This experiment examined the effectiveness of inhibitors over a 3-year period when used with several N sources with varying ammonium-N contents, all applied at emergence on an irrigated loamy sand in central Wisconsin. In 3 of 6 site-years, use of an inhibitor increased total tuber yield with one or more of the N sources. Inhibitor use also sometimes increased tuber N accumulation and apparent recovery of applied fertilizer N. However, in 4 of 6 site-years, inclusion of an inhibitor with all-ammonium fertilizer N decreased harvested U.S. No. 1 tubers. This decrease was primarily due to an increased proportion of off-shape cull tubers, likely in response to the aversion of potato to ammonium nutrition. While use of inhibitors may have some application for potato production on irrigated sandy soils, it is clear that when they are used, the N fertilizer should be a mixed ammonium/nitrate fertilizer source.

Nutrient and carbon balances in organic vegetable production on an irrigated, sandy soil in northern Oman

AbstractOur understanding of nutrient and carbon (C) fluxes in irrigated organic cropping systems of subtropical regions is limited. Therefore, leaching of mineral nitrogen (N) and phosphorus (P), gaseous emissions of NH3, N2O, CO2, and CH4, and total matter balances were measured over 24 months comprising a total cropping period of 260 d in an organic‐cropping‐systems experiment near Sohar (Oman). The experiment on an irrigated sandy soil with four replications comprised two manure types (ORG1 and ORG2) characterized by respective C : N ratios of 19 and 25 and neutral detergent fiber (NDF)‐to‐soluble carbohydrates (SC) ratios of 17 and 108. A mineral‐fertilizer (MIN) treatment with equivalent levels of mineral N, P, and potassium (K) served as a control. The three treatments were factorially combined with a cropping sequence comprising radish (Raphanus sativus L.) followed by cauliflower (Brassica oleracea L. var. botrytis) or carrot (Daucus carota subsp. sativus). Over the 24‐months experimental period gaseous N emissions averaged 45 kg ha–1 (59% NH3‐N, 41%N2O‐N) for MIN, 55 kg N ha–1 (69% NH3‐N, 31%N2O‐N) for ORG1, and 49 kg N ha–1 (59% NH3‐N, 41% N2O‐N) for ORG2. Carbon losses were 6.2 t ha–1 (98% CO2‐C, 2% CH4‐C) for MIN, 9.7 t C ha–1 (99% CO2‐C, 1% CH4‐C) for ORG1, and 10.6 t ha–1 (98% CO2‐C, 2% CH4‐C) for ORG2. Exchange resin–based cumulative leaching of mineral N amounted to 30 kg ha–1 for MIN, 10 kg ha–1 for ORG1, and 56 kg ha–1 for ORG2. Apparent surpluses of 361 kg N ha–1 and 196 kg P ha–1 for radish‐carrot and 299 kg N ha–1 and 184 kg P ha–1 for radish‐cauliflower were accompanied by K deficits of –59 kg ha–1 and –73 kg ha–1, respectively, for both cropping systems. Net C balances for MIN, ORG1, and ORG2 plots were –7.3, –3.1, and 1.5 t C ha–1 for radish‐carrot and –5.0, 1.3, and 4.6 t C ha–1 for radish‐cauliflower. The results underline the difficulty to maintain soil C levels in intensively cultivated, irrigated subtropical soils.