The evaluation of potato response to controlled-release fertilizers (CRFs), as a sole source of nitrogen (N) or as a blend with a soluble N source, is essential to 1) develop the best management recommendations for using CRFs in potato production and 2) provide guidelines to CRF manufacturers for developing an optimal product. This study aimed to evaluate the potato yield and quality responses to N CRFs (polymer-coated urea [PCU]) vs soluble N sources. The experiments were conducted in major potato-growing regions in the United States and China. The current industry-recommended practice of 112 kg N/ha pre-plant soil broadcast of urea plus five in-season fertigations of 224 kg N/ha as urea ammonium nitrate (UAN-32) was compared to a single pre-plant application of 224 kg N/ha as a CRF as the sole source of N or as multiple blends of CRFs and soluble N sources (i.e., urea) at various ratios. The results demonstrated that petiole nitrate_N (NO3_N) levels and tuber yield with single pre-plant broadcast applications of 224 kg N/ha as CRF/urea blends (ratio of 25/75 or 50/50) were similar to those obtained with industry-standard N management practice. N uptake and yield were significantly greater with 220 kg/ha N as the CRF than those with the same N rate as urea. Unlike the current potato industry N practice, using CRFs as either a sole source of N or blended with urea reduces the total N rate and application frequency.

A 2-year study was conducted to assess the effects of irrigation regimes using saline water on soil salinization, yield, water productivity, and net income of faba bean (Vicia faba L.) under actual farming conditions in arid regions of Tunisia. Faba bean (cvs. Luz de Otono and local) was grown on a sandy soil and drip-irrigated with water having an electrical conductivity of 6 dS m(-1). Two deficit irrigation (DI70 and DI40) and one full irrigation (FI) strategy consisting of applications of 40%, 70%, and 100% of crop evapotranspiration (ETc), respectively, were compared to the traditional farmers' irrigation method (FM) in which 16 mm irrigation were applied every 5 days from planting till harvest. Results showed that the lowest soil salinity values at harvest were observed under FI treatment, while the highest were obtained with DI40 and the FM. The maximum values of faba bean yields were obtained under FI and the lowest with the FM. No significant reduction in yields was observed with the DI70 treatment compared to FI, while DI40 and the FM significantly decreased the fresh pod yields. Using 12%-20% more irrigation water than FI treatment, the FM did not improve soil salinity but resulted in a significant yield reduction compared to FI. Total water productivity values varied between 4.9 (FM) and 14 kg m(-3) (DI40) across different years and treatments. Compared to the FM, which applies fixed amounts with the same frequency, the FI strategy, which adapts the irrigation amounts to the actual crop water requirements, was more productive and provided a significant advantage in terms of yield and net income. Under limited availability of irrigation water, adoption of the DI70 treatment was found to be a good alternative as it allowed 30% water saving and was subject to limited negative effects on soil salinity, yield, and net income.

The transport and fractionation of copper (Cu) were investigated in three soils which were under continuous citrus production for over 30 years. The above soils received 50 kg Cu ha−1, and were leached with eight pore volumes of water (equivalent to a total of 91 cm of rainfall). Following the completion of leaching, the leaching columns were sectioned into 5 cm depth increments for analyses of soil Cu. Concentrations of different forms of soil Cu were analyzed using a sequential fractionation procedure. The leaching column study indicated as much as 98% of the applied Cu remained in the upper 5 cm of the soil despite leaching eight pore volumes of water. Copper recovered in eight pore volumes of leachate accounted for 0.18–2.87% of Cu applied. The organically bound and precipitated forms of Cu accounted for 33–87% and 6–44% of total soil Cu, respectively.

Increasing the retention of nutrients by agricultural soils is of great interest to minimize losses of nutrients by leaching and/or surface runoff. Soil amendments play a role in nutrient retention by increasing the surface area and/or other chemical processes. Biochar (BC) is high carbon-containing by-product of pyrolysis of carbon-rich feedstocks to produce bioenergy. Biosolid is a by-product of wastewater treatment plant. Use of these by-products as amendments to agricultural soils is beneficial to improve soil properties, soil quality, and nutrient retention and enhance carbon sequestration. In this study, the adsorption of NH4-N, P, and K by a sandy soil (Quincy fine sand (QFS)) and a silty clay loam soil (Warden silty loam (WSL)) with BC (0, 22.4, and 44.8 mg ha−1) and biosolid (0 and 22.4 mg ha−1) amendments were investigated. Adsorption of NH4-N by the QFS soil increased with BC application at lower NH4-N concentrations in equilibrium solution. For the WSL soil, NH4-N adsorption peaked at 22.4 mg ha−1 BC rate. Biosolid application increased NH4-N adsorption by the WSL soil while decreased that in the QFS soil. Adsorption of P was greater by the WSL soil as compared to that by the QFS soil. Biosolid amendment significantly increased P adsorption capacity in both soils, while BC amendment had no significant effects. BC and biosolid amendments decreased K adsorption capacity by the WSL soil but had no effects on that by the QFS soil. Ca release with increasing addition of K was greater by the WSL soil as compared to that by the QFS soil. In both the soils, Ca release was not influenced by BC amendment while it increased with addition of biosolid. The fit of adsorption data for NH4-N, P, and K across all treatments and in two soils was better with the Freundlich model than that with the Langmuir model. The nutrients retained by BC or biosolid amended soils are easily released, therefore are readily available for the root uptake in cropped soils.

A large field potato experimental data set has been assembled for simulation modeling. The data are from temperate, subtropical, and tropical regions across the world and include 87 experiments with 204 treatments. Treatments include nitrogen fertilizer, irrigation, atmospheric CO2 levels, temperature, cultivars, and locations. For all experiments, measurements include tuber fresh and dry weight. For some experiments, measurements include in-season biomass, leaf area index, stem and leaf weight, N uptake, soil water, and soil N contents. Each experiment has soil characteristics and daily data for solar radiation, rainfall, and maximum and minimum temperature. The data have been quality checked and used in a previous simulation exercise. All data are in AGMIP format. Data access via doi 10.7910/DVN/4KJ5ME.

Crop models are essential tools in climate change impact assessments, but they often lack comprehensive field testing. In this study, we tested the SUBSTOR-potato model with 87 field experiments, including 204 treatments from 19 countries. The field experiments varied in potato species and cultivars, N fertilizer application, water supply, sowing dates, soil types, temperature environments, and atmospheric CO2 concentrations, and included open top chamber and Free-Air-CO2-Enrichment (FACE) experiments. Tuber yields were generally well simulated with the SUBSTOR-potato model across a wide range of current growing conditions and for diverse potato species and cultivars, including Solanum tuberosum, Solanum andigenum, Solanum juzepczukii species, as well as modern, traditional, early, medium, and late maturity type cultivars, with a relative RMSE of 37.2% for tuber dry weight and 21.4% for tuber fresh weight. Cultivars 'Desiree' and 'Atlantic' were grown in experiments across the globe and well simulated using consistent cultivar parameters. However, the model underestimated the impact of elevated atmospheric CO2 concentrations and poorly simulated high temperature effects on crop growth. Other simulated crop variables, including leaf area, stem weight, crop N, and soil water, differed frequently from measurements; some of these variables had significant large measurement errors. The SUBSTOR-potato model was shown to be suitable to simulate tuber growth and yields over a wide range of current growing conditions and crop management practices across many geographic regions. However, before the model can be used effectively in climate change impact assessments, it requires improved model routines to capture the impacts of elevated atmospheric CO2 and high temperatures on crop growth. (C) 2016 Elsevier B.V. All rights reserved.

The water withdrawals for agriculture across the United States account for 25–50%, unlike in the dry regions of the world this proportion can be >75–90%. About 57% of the total irrigated acreage in the US is in six states (California, Nebraska, Texas, Arkansas, Idaho, and Colorado), with the remaining states accounting for only 43% of the irrigated acreage. Western states represent the high percent of farmland under irrigation, i.e. 25–40% with some areas >40%. Surface water accounts for a larger portion of total irrigation water withdrawals in the western states, unlike the mid-western and the southern states where groundwater is the major source of irrigation water. The northeastern states show mixed trend, with both surface and groundwater contributing for irrigation water withdrawals. Real time, automated measurement of soil water, temperature, and electrical conductivity in the soil profile, within and below the root zone, is a critical component of best management of nutrients and irrigation aimed to optimize nutrient and water uptake efficiency while minimizing potential leaching of nutrients and water below the root zone. A case study described in this paper was conducted in a potato (cv. Umatilla Russet) and corn field on Quincy fine sand (mixed, mesic, Xeric Torripsamments) under center pivot irrigation in eastern Washington State. Annual precipitation in this region is about 160 mm with only 20% of this amount received during the growing season, i.e. May through August. Therefore, careful management of irrigation is critical to enhance water use efficiency and water productivity. Sensors were used for automated monitoring of soil water content, temperature, and electrical conductivity on a real-time basis at different depths in the soil profile to represent root zone (0–60 cm) and below the root zone (>60 cm). The utility of real time monitoring of soil water data for developing the irrigation set points to maintain the soil water content in the root zone within the management allowed deficit (MAD) to mitigate any impact of water stress while minimizing the water percolation below the root zone are discussed. Similar technologies using user friendly but low cost sensors have been tested in small farms in India (Punjab and Haryana) over the past year. The sensors use capacitance to determine volumetric soil water content in the root zone (0–30 cm). Farmers were advised on the soil water threshold values to be maintained for different crops (spinach, okra, cauliflower, bitter gourd, and rice). While these sensors resulted in initial high adoption of 80% of advisories, the efficacy was reduced after a short period. A new technology, where the sensors automatically control irrigation set points is now being tested. Initial feedback suggests that farmers have a greater level of confidence in the automation, leading to increased and longer adoption rates. This technology is now being tested in only a few sites; will be expanded across three more states in India.

Nitrate (NO3) leaching is a significant nitrogen (N) loss process for agriculture that must be managed to minimize NO3 enrichment of groundwater and surface waters. Managing NO3 leaching should involve the application of basic principles of understanding the site's hydrologic cycle, avoiding excess rates of N, and applying N in phase with crop demand. Other specific techniques to reduce NO3 leaching are presented in this entry.

Biochar, byproduct of pyrolysis for bioenergy production, is a good adsorbent of nutrients and pollutants from wastewater (WW). Efficiency of nutrient removal by biochar is dependent on the feedstock used. Removal of nitrogen (N) and phosphorus (P) from WW was evaluated using a commercial biochar, from Dynamotive company (DY), activated carbon (AC), or biochars produced from peanut hull (PH), bagasse (BG) or hickory wood (HW), at rates 2.5 to 100 g L -1 WW. Removal of NH4-N by DY and PH biochars increased significantly with an increase in biochar rate. In the case of BG and HW biochars, the highest removal of NH 4 -N was at 25 g L -1 rate. Removal of NH 4 -N by AC was extremely low, except at 100 g L -1 rate. The Ortho-P adsorption from WW increased with increasing rates of biochar, except for PH biochar. This study demonstrated that most of the biochars, except PH biochar, are more effective than AC in removal of NH 4 -N and P from wastewater. The N and P enriched biochar can be used as soil amendment to agricultural soils to supply nutrients and enhance carbon sequestration.

•Biochar and diary effluent were applied to corn grown on a Warden Silt loam soil.•Soil biochemical properties were significantly influenced by biochar.•Principal component analysis based soil quality index equation was developed.•Biochar and fertilization improved soil quality index.

Estimation of N uptake efficiency of fertilizer applications at different growth stages of crop plants is critical to develop management recommendations that enhance fertilizer use by minimizing N losses. In this study, the N-fertilizer uptake efficiency (FNUE) of two chipping potato (Solanum tuberosum L.) varieties (‘Atlantic’ and ‘FL1867’) under three typical fertilizer application timings was investigated. All treatments received a total of 225 kg ha−1 of N throughout the season, split into three applications of 75 kg ha−1 as ammonium nitrate (NH4NO3) applied at pre-plant, plant emergence and tuber initiation. FNUE at each application timing was evaluated by the substitution of conventional N-fertilizer by isotope labeled ammonium nitrate (15NH 4 15 NO3). Total tuber yield was similar between the two varieties at 48.8 and 37.5 Mg ha−1 in 2013 and 2014, respectively. Likewise, the overall FNUE was also similar at 45 % across both varieties and years. FNUE was 11 % for the pre-plant application, while 62 % for the applications at emergence and tuber initiation stages. Since a small fraction of the N applied at pre-plant was recovered in the plant, N fertilizer application closer to the potato planting may increase the FNUE.

A potato crop multimodel assessment was conducted to quantify variation among models and evaluate responses to climate change. Nine modeling groups simulated agronomic and climatic responses at low‐input (Chinoli, Bolivia and Gisozi, Burundi)‐ and high‐input (Jyndevad, Denmark and Washington, United States) management sites. Two calibration stages were explored, partial (P1), where experimental dry matter data were not provided, and full (P2). The median model ensemble response outperformed any single model in terms of replicating observed yield across all locations. Uncertainty in simulated yield decreased from 38% to 20% between P1 and P2. Model uncertainty increased with interannual variability, and predictions for all agronomic variables were significantly different from one model to another (P < 0.001). Uncertainty averaged 15% higher for low‐ vs. high‐input sites, with larger differences observed for evapotranspiration (ET), nitrogen uptake, and water use efficiency as compared to dry matter. A minimum of five partial, or three full, calibrated models was required for an ensemble approach to keep variability below that of common field variation. Model variation was not influenced by change in carbon dioxide (C), but increased as much as 41% and 23% for yield and ET, respectively, as temperature (T) or rainfall (W) moved away from historical levels. Increases in T accounted for the highest amount of uncertainty, suggesting that methods and parameters for T sensitivity represent a considerable unknown among models. Using median model ensemble values, yield increased on average 6% per 100‐ppm C, declined 4.6% per °C, and declined 2% for every 10% decrease in rainfall (for nonirrigated sites). Differences in predictions due to model representation of light utilization were significant (P < 0.01). These are the first reported results quantifying uncertainty for tuber/root crops and suggest modeling assessments of climate change impact on potato may be improved using an ensemble approach.

Over many years, high phosphorus (P) loading for intensive vegetable cropping in greenhouses of North China has contributed to excessive P accumulation, resulting in environmental risk. In this study, the influences of manure and nitrogen (N) application on the transformation and transport of soil P were investigated after nine years in a greenhouse tomato double cropping system (winter-spring and autumn-winter seasons). High loading of manure significantly increased the soil inorganic P (Pi), inositol hexakisphosphate (IHP), mobile P and P saturation ratio (PSR, >0.7 in 0-30 cm depth soil; PSR was estimated from P/(Fe + Al) in an oxalate extract of the soil). The high rate of N fertilizer application to the studied calcareous soil with heavy loading of manure increased the following: (i) mobile organic P (Po) and Pi fractions, as evidenced by the decrease in the ratio of monoesters to diesters and the proportion of stable Pi (i.e., HCl-Pi) in total P (Pt) in 0-30 cm depth soil; (ii) relative distribution of Po in the subsoil layer; and (iii) P leaching to soil depths below 90 cm and the proportion of Po in Pt in the leachate. More acidic soil due to excessive N application increased P mobility and leaching. The increase in Ox-Al (oxalate -extractable Al) and the proportion of microbe-associated Po related to N application at soil depths of 0-30 cm suggested decrease in the net Po mineralization, which may contribute to downward transport of Po in the soil profile. (C) 2016 Elsevier Ltd. All rights reserved.

This study evaluated the petiole uptake of nitrogen, phosphorus, potassium, and sulfur (N, P, K, and S) by the potato from two seed meals, mint compost, and five commercially available organic fertilizers under an irrigated certified organic production system. Available soil nitrate (NO3-N) and ammonium (NH4-N) from each amendment averaged 115 kg N ha(-1) at application and 25 kg N ha(-1) 30 d after planting through harvest, with minor differences between fertilizers. Petiole N declined from an average of 25,000 mg N kg(-1), 4 wk after emergence to 3,000 mg N kg(-1) prior to harvest. Petiole P and K concentrations were maintained above 4,000 mg P kg(-1) , 10,000 mg K kg(-1), and 2,000 mg S kg(-1) tissue, respectively, throughout the growing season in all treatments. Tuber yields were not different between fertilized treatments averaging 53 Mg ha(-1) . This study provides organic potato growers baseline information on the performance of a diverse array of organic fertilizers and amendments.

Field experiments were performed to study potato response to irrigation regimes using saline water on a sandy soil in southern Tunisia during the years 2011-2014. Irrigation regimes consisted in the replenishment of cumulated ETc when 35% of the root zone holding capacity is depleted at levels of 100% (I100), 70% (I70) and 40% (I40). The farmer used a fixed irrigation dose and interval, applying 16mm every 4days from planting till harvest. Higher soil salinity is observed at harvest under I40 and farmer treatments compared to I100. Highest potato yield was obtained with I100 treatment (24.4-27.5 t ha(-1)) across 3 years. Significant reductions in yields were observed under I70 and I40 as compared to I100. The farmer's method also caused significant reductions in yield and resulted in using 15-22% more irrigation water than I100. Water productivity (WP) values varied between 4.3 kgm(-3) (farmer) and 18.5 kgm(-3) (I40) across different years and treatments. The scheduling technique using the soil water balance (SWB) with variable amounts is more efficient than the farmer's method. Full and deficit treatments (I100 and I70) generated the highest net income. I100 appears to be a promising irrigation strategy for the potato crop in the arid climate of Tunisia. Nonetheless, under water scarcity, irrigation of potato could be scheduled using I70 deficit strategy, with some yield reductions (12.5-23.0%). Copyright (C) 2016 John Wiley & Sons, Ltd.

The Columbia Basin in the Pacific Northwest is a highly productive area for potatoes in the United States. Here, nitrate is the most frequently documented groundwater contaminant, and the challenge of maximizing crop productivity while minimizing the nitrate pollution still remains. This study assessed the responses of tuber yield, nitrate leaching, and profit margin to irrigation water amount, irrigation interval, nitrogen application rate, and soil type using 30 years of historical weather data and two representative soils in three locations of this region. A potato model was used to simulate the response variables for a total of 7500 scenarios (5 irrigation intervals x 5 irrigation amounts x 5 nitrogen rates x 2 soil types x 30 years) for each location. The results showed that nitrate leaching was greater with a larger irrigation, a longer irrigation interval, a higher nitrogen rate, and a lighter soil. Tuber yield was larger with a smaller irrigation, a higher nitrogen rate, and a heavier soil. Profit margin was larger with a smaller irrigation and a heavier soil. The optimum amount of irrigation water for the study region was 400 mm, at which both tuber yields and profit margins were the largest with the nitrogen application rate of 336 kg ha(-1). The increase in leaching with a larger irrigation was smaller for a longer irrigation interval and a lighter soil but larger for a higher nitrogen rate. These findings might be helpful to potato growers in this region in identifying irrigation and nitrogen application rates aimed toward maximizing yields and profits while minimizing the nitrate contamination of groundwater. (C) 2016 Elsevier B.V. All rights reserved.

Aboveground biomass of sugar beet influences tuber growth and sugar accumulation. Thus, accurate, rapid, and non-destructive technique of biomass estimation is important to optimize the crop management practices to attain the required aboveground biomass to support high tuber yields and optimal sugar content. The current research aimed to evaluate the performance of hyperspectral indices and band depth analysis, to remotely assess the aboveground biomass in sugar beet. The biomass and hyperspectral reflectance were collected at different growth stages in experimental and farmers’ fields. The model development was based on sugar beet plants sampled at various times during the growing period subject to seven nitrogen rates. The results showed that accuracy of biomass estimation was greater when using vegetation indices involving red edge bands (680–740 nm) as compared to that using the red light-based indices. Four types of optimized band depth information (band depth, band depth ratio, normalized band depth index, and band depth normalized to band area) involving the red edge further increased the accuracy of biomass estimation. This study demonstrated as the sugar beet biomass increased towards later growing period, biomass estimation using red light-based vegetation indices were less accurate as compared to that using band depth analysis in the vicinity of the red edge.

Effects of supplemental nitrogen (N), as either farmyard manure (FYM) or urea, on response of two wheat ( Triticum aestivum ) cultivars (a salt sensitive ‘Sakha 69’ and a salt tolerant ‘Sakha 93’) were investigated in a green house experiment under various salinity levels (control, 6, 9, or 12 dS m -1 ). Grain and straw yields of both cultivars decreased with an increase in salinity levels. Supplamental N application, using FYM or urea, mitigated the adverse effects of salinity only at the low salinity level (6 dS m -1 ). This effect was greater in a salt tolerant cultivar (Sakha 93) than that in a salt sensitive cultivar (Sakha 69). At the moderate and high salinity (9 and 12 dS m -1 ) levels the supplemental N had no beneficial effects in mitigating the salinity stress of both cultivars. The mean grain yields, across all salinity levels and cultivars, of the plants received FYM and urea were greater by 11, and 8%, respectively, as compared to that of the plants received no supplemental N. The corresponding values for straw were 12 and 7%. The concentrations of N, P and K in the grain and straw significantly decreased with increasing salinity levels. Concentrations of Na, Cl, and Ca in the grain and straw were greater in salt sensitive cultivar than those in a salt tolerant cultivar. Concentrations of these elements significantly increased with an increase in salinity levels. This study demonstrated that supplemental N, as either FYM or as Urea, can mitigate negative effects of mild salinity stress, and that this beneficial effect was greater in a salt tolerant cultivar as compared to that in a salt sensitive cultivar.