Field Capacity Moisture Content Research Articles

Characteristics of soil physical properties in different soil management of oxisols and inceptisols

Oil palm (Elaeis guineensis Jacq.) is a plantation crop that has a bright future. Soil management such as land clearing, burning, use of heavy equipment and fertilisation in oil palm plantations will affect changes in soil physical properties. This study aims to assess the physical properties of soil in various treatments (planting circle, dead interplant spacings and live interplant spacings) on Oxisol and Inceptisol soil types. This research was conducted in Rancabungur and Malingping Banbten in October 2021 - May 2022. The method used in this study was multistage random sampling. Soil samples were taken from the Malingping area of Banten for the Oxisol soil type (2005 and 2009 planting years), and the Rancabungur area for the 2005 Inceptisol soil type. Comparison of soil physical properties of Oxisol of 2005 planting year with Oxisol of 2009 planting year and the ratio of Oxisol soil type of 2005 planting year and Inceptisol of 2005 planting year in various treatments did not show significant differences in soil physical properties (organic matter, content weight, field capacity moisture content, permanent wilting point, and particle density) between planting circle, dead interplant spacings and live interplant spacings. However, there were significant differences in the physical properties of soil texture between each management and permeability.

ANALISIS KEBUTUHAN AIR TANAMAN SELADA (Lactuca sativa L.) PADA INCEPTISOL DAN VERTISOL BERBASIS INTERNET OF THINGS (IoT)

Lactuca sativa L. has good economic prospects, but lettuce production often declines due to the unmet water requirement of lettuce. This study aimed to determine the water needs of lettuce on Inceptisol and Vertisol based on the Internet of Things (IoT). The location study was in the green house, Huluduotamo Village, Bone Bolango Regency, from September to October 2021, while the Vertisol and Inceptisol samples were from Sidomukti Village, Gorontalo Regency. This study used the Penman method with the Cropwat 8.0 application which was integrated with a smartphone through the Blynk (IoT) application. The water requirement yield of lettuce plants in September on Vertisol and Inceptisol in the early phase was 2.45 mm/day, the middle phase was 3.73 mm/day, and the final phase was 3.54 mm/day. Soil moisture detection device at field capacity moisture content produces 319 Analog Digital Converter (ADC) and soil in moist conditions reaches 534 ADC. The analog data value of the water content of the Inceptisol field capacity is 343 ADC and the soil in a moist state is 574 ADC. The performance of the device for detecting soil moisture in the water condition of the 15% field capacity of Vertisol and 22% Inceptisol is more effective than the gravimetric method.

Analysis Of Water Requirements For Irrigation Of Green Honey Water Apple (Syzygium aqueum) In Pots

Plant irrigation water needs are important things to be met so that the plant growth is optimal starting from the vegetative phase to the generative phase. The current hot issue among potted fruit growers is the problem of dropping the ovary (pistil) on the plant. Many factors cause the fall of plant fruit, one of which is lack of water. This certainly needs special attention considering the nature of the water apple plant itself, in this study, especially the green honey water apple, it consumes quite a lot of water every day. To overcome the problem of water shortages in the green honey water apple plant, it is necessary to first know the average plant water requirement in pots through water content analysis in the laboratory at three stages of analysis and calculation of Pot Water Requirements (PWR) and Efficiency Needs Irrigation Water. Average Field Capacity Moisture Content of the potted planting media sample was 49.37%, Air Dry Moisture Content was 24.27 % and PWR 4.36 liters with an efficiency of irrigation water requirement for bulk systems (hand move or portable) of 5, 12-5.81 liters and a drip irrigation system (point source emitter) of 4.84-5.45 liters.

STUDI SIFAT FISIK TANAH PADA KEBUN KARET DAN KELAPA SAWIT DI DESA RASAN KECAMATAN NGABANG KABUPATEN LANDAK

This study aimed to compare the physical properties of soil on rubber and oil palm plantation in the village of the District Rasan Ngabang Porcupine District. Observation point soil samples taken at rubber plantations and palm oil to a depth of 0-30 cm and 30-60 cm. Parameter observations used in this study consists of the characteristic physical properties of the soil that is the color of the soil, soil structure, soil texture, bulk density soil, the water content of field capacity, soil porosity, permeability, stability of soil aggregates, content of organic C, N-total , C / N ratio, and soil reaction (pH).The observation of the color of the soil in the field on rubber plantations and palm oil is known that, there are some differences and similarities at each point of observation well was at a depth of 0-30 cm and 30-60 cm. The structure of a rubber garden soil to a depth of 0-30 cm and 30-60 cm blocky rounded grains (granular) while in the oil palm plantation with a depth of 0-30 cm and 30-60 cm soil structure is blocky angular. While the texture of the soil at a depth of 0-30 cm rubber plantations and 30-60 cm termaksuk sandy clay loam and clayey loam soil texture while the oil palm plantation with a depth of 0-30 cm and 30-60 cm including sandy clay loam, clay and loam clayey.T test results on soil bulk density rubber plantations and palm oil at a depth of 0-30 cm showed significantly different while the depth of 30-60 cm are not significantly different, while the t-test, field capacity moisture content in the rubber plantations and palm oil at a depth of 0-30 cm showed significantly different at a depth of 30-60 cm while not significantly different. The results of the t test soil porosity rubber plantations and palm oil at a depth of 0-30 cm and 30-60 cm are not significantly different. While the t-test, soil permeability in rubber plantations and palm oil to a depth of 0-30 cm and 30-60 cm showed no significant difference.Soil aggregate stability was higher in oil palm plantations over rubber either the depth of 0-30 cm and 30-60 cm. While the results of the analysis of organic materials in the rubber plantations and palm oil is low to very low both at a depth of 0-30 cm and 30-60 cm, N-total is low to very low, and C / N ratio is low and soil reaction ( pH) sour to very sour.

EFFECT OF COMPOST DOSES ON SOIL RESILIENCE IN PALU VALLEY

Applying organic matter to the soil surface is an effective effort to increase soil resilience in the Palu valley, which is classified as low. This study aimed to determine: 1) the effect of several doses of compost on the physico-chemical properties of the soil, 2) the correlation between the percentage of organic carbon and total nitrogen in the soil to several physico-chemical properties of the soil. The research was based on a randomized block design in a greenhouse of the Faculty of Agriculture, Tadulako University, Palu. Compost uses raw materials for plantain stems (Musa textilia) and leaves of Gamal (Gliricidia sepium). The compost doses used in the experiment consisted of 0%, 1%, 2%, 3%, 4%, and 5% of the weight of air-dry soil, respectively. The treatment was repeated three times. The results showed that compost application significantly affected soil content weight, total porosity, saturated hydraulic conductivity, field capacity moisture content, percentage of organic carbon, total nitrogen, and cation exchange capacity. The correlation test results showed a powerful relationship between the percentage of organic carbon or total soil nitrogen to other soil physico-chemical properties observed in the experiment.

A laboratory assay of in situ stabilization of toxic metals in contaminated boreal forest soil using organic and inorganic amendments

Metal-contaminated soils present a great threat to natural ecosystems and human health. Remediation studies focusing on metal-polluted soils with high organic matter (OM > 20%) are limited. This study evaluated the effectiveness of biochar, compost, diammonium phosphate (DAP), and iron oxides (Fe-O), in immobilizing metals from an OM-rich boreal forest soil contaminated with arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). A laboratory incubation study was conducted with soil amended with biochar (5% w w−1), compost (5% w w−1), DAP (0.2% w w−1), or Fe-O (0.2% w w−1), and a control (without amendment) for 6 months at field capacity moisture content. Metal concentrations were determined in pore water collected at 0, 2, 4, and 6 months after incubation. Soil was extracted sequentially for metals after the incubation period. Metal concentrations in pore water were significantly reduced by different amendments as follows: As by biochar and Fe-O, Cd by biochar, compost, and DAP, Cu by biochar, Pb by compost and DAP, and Zn by biochar and compost. Sequential extractions revealed biochar and (or) compost transferred Cd, Cu, Pb, and Zn from the labile pool to the non-labile pool confirming their effectiveness as amendments for remediation of metal-contaminated OM-rich boreal forest soil.

Changes in recovery of native and applied phosphorus with time as affected by soil properties in some calcareous soils

ABSTRACTIn an attempt to investigate variations in availability of native and applied phosphorus (P) with time, twenty five calcareous soil samples were treated with 0, 50 and 500 mg P kg−1 soil and incubated at 80–90% of field capacity moisture content in an open door glasshouse for a period of one year. Soil samples were taken out at certain intervals for P extraction with Olsen extractant under moist condition. Results indicated that following wetting the mean value of native Olsen-P decreased initially and then increased gradually with time of incubation. Generally, the short term (24 h) recoveries were not correlated with long term ones. The recovery of added P with time was described properly by the following new proposed model: R = 100/(1 + ktb), where R is percent recovery at time t, and k and b are empirical parameters. The values of k constant at 50 and 500 mg P kg−1 were in the ranges of 0.40 to 1.22 (0.84 ± 0.25, on average) and 0.04 to 0.52 (0.23 ± 0.14, on average), respectively. The corresponding respective values of b constant also ranged from 0.05 to 0.32 (0.15 ± 0.06, on average) and 0.12 to 0.92 (0.46 ± 0.23, on average).

Effect of Incubation Duration of Incorporated Organics on Saturated Hydraulic Conductivity, Aggregate Stability and Sorptivity of Alluvial and Red-Laterite Soils

Improvement in soil hydro-physical properties is a pre-requisite for maintaining soil quality and sustaining agricultural productivity. The objective of this study was to see the effect of degree of decomposition of farmyard manure (FYM) and vermicompost on aggregation indices viz., water stable aggregate (WSA), mean weight diameter (MWD) and aggregate stability (AS), and water transmission properties namely, saturated hydraulic conductivity (Ks) and sorptivity (S) of two contrasting soils (red-laterite and alluvial soils). Soils were incubated with FYM and vermicompost @ 20 t ha−1 for 60 days at field capacity moisture content under laboratory condition and analyzed at 0, 20, 40 and 60 days of incubation (DOI) for hydrophysical and soil organic carbon (SOC) content. Results indicated that the influence of organics was more predominant in red-laterite soil having more iron and aluminium oxides and lower clay content than alluvial soil. Upon incubation, the organic treated red-laterite and alluvial soils increased 73 and 15 per cent SOC, 16 and 13 per cent micro-porosity, 119 and 412 per cent Ks, 25 and 19 per cent WSA, 45 and 11 per cent MWD and 31 and 26 per cent S, respectively. Similarly, vermicompost and FYM treated soils increased 44 and 43 per cent SOC, 17 and 11 per cent micro-porosity, 622 and 239 per cent Ks, 31 and 13 per cent WSA, 33 and 24 per cent MWD and 46 and 11 per cent S. Bulk density (BD) varied from 1.54 to 1.38 and 1.31 to 1.24 Mg m−3, respectively for red-laterite and alluvial soils during the entire incubation period with a strong negative relationship (r =-0.97, p< 0.001) with micro-porosity. Strong positive correlations between WSA and SOC (r = 0.58, p < 0.01), MWD and SOC (r = 0.74, p < 0.001) and AS and SOC (r = 0.73, p < 0.001) were observed indicating that the AS would increase 3.8 per cent with the increase in SOC by 1% in both soils. Sorptivity was positively and significantly related to SOC (r = 0.55, p<0.01) and micro-porosity (r = 0.51, p<0.01), however, had a negative relationship with BD (r =-0.51, p<0.01). Vermicompost had shown better results in structural as well as hydro-physical properties as compared with FYM in both soils.

Basil (Ocimum basilicum L.) water needs calculated from the crop coefficient

The determination of the crop coefficient (Kc) throughout the phenological stages is important for the calculation of water requirements of plants. This study determined the Kc curve for Basil (Ocimum basilicum L.) in Candelaria, Valle del Cauca, and evaluated this Kc in greenhouse conditions. Three drainage lysimeters and a portable meteorological station were used to determine the reference evapotranspiration (ETo), which were set up randomly in an experimental plot. The field capacity (FC) moisture content was determined, and the soil moisture and drainage depth were periodically monitored. Daily water balance calculations were conducted to determine the crop’s water needs (ETc), and the Kc was calculated based on the quotient between ETc and ETo by performing statistical regression analysis. In the second experiment, in a completely randomized bifactorial design, four treatments were established in Cali (Valle). These treatments were amount of water necessary to maintain the soil moisture at FC and amount of water calculated with the Kc (72 % FC), both treatments with and without fertilizers application. The results showed that the Kc values for basil are: growth stage, 0,45 ± 0,02 (25 days after transplant, dat); maturity stage, 0,59 ± 0,02 (26 – 50 dat); and senescence stage, 0,42 ± 0,03 (51 – 71 dat). In greenhouse conditions, dry mass percentage, plant height, soil pH and electrical conductivity were similar for both water regimens. The reduction on water with Kc increased the nitrogen foliar but the water use efficient decreased.

Chemical forms of cadmium in a calcareous soil treated with different levels of phosphorus-containing acidifying agents

Calcareous soils with high background cadmium (Cd) levels are widely distributed in south-west China and soil acidity is a major environmental problem. However, little effort has been made to study the changes in chemical speciation as affected by soil acidification other than by acidic rain. In the present study, we investigated the impact of mono-ammonium phosphate (MAP) and phosphoric acid on soil pH and chemical transformation of Cd in calcareous soils. Calcareous soils collected from south-west China were treated with three concentrations (0.1, 0.2 and 0.4 mol kg–1 soil) of MAP and phosphoric acid, and without the addition of acidifying agent, before being incubated at 25 ± 2°C near field capacity moisture content for 60 days. The chemical forms of Cd in the soils were determined by the Tessier sequential extraction scheme. The concentration of Cd in the form bound to iron and manganese oxides (CdFeOx+MnOy) decreased significantly with increasing levels of the two acidifying agents, but the concentration of exchangeable Cd (CdEx) exhibited a significant increase, indicating that the two acidifying agents can effectively promote the transformation of CdFeOx+MnOy to CdEx. MAP may promote the same amount of CdFeOx+MnOy to CdEx as phosphoric acid at the same rate of addition, but the soil pH clearly differed, implying that an increase in water-soluble P with addition of acidifying agent may be one major factor affecting the chemical transformation of Cd. MAP and phosphoric acid should be used carefully as sources of water-soluble phosphorus for calcareous soils with high background concentrations of Cd.

Phosphate minerals and solubility in native and agricultural calcareous soils

Generally the direct identification of naturally occurring phosphate minerals, especially the reaction products of applied phosphate fertilizer with soil constituents, is very difficult. Nevertheless the characterization of phosphate (P) minerals and the understanding of their behavior in soils are very important with respect to fertilizer management and to safeguarding water quality. The objectives of this study were to determine the P minerals detectable in different particle size fractions of native and cultivated calcareous soils that are probably products of reactions between the soil and the fertilizer, and to examine the relationships between P mineral composition, phosphate solubility, chemical fractionation, and P activity. Fifteen calcareous soils representing four soil series were collected from native pineland and wetland, cultivated vegetable fields and fruit groves in south Florida. Soil samples were separated into sand, silt and clay with and without the removal of CaCO3 and organic matter. Mineralogy of selected fractions was determined by X-ray diffraction (XRD). Relatively distinctive crystalline apatite was identified by XRD of high-density separates from carbonate-free silt fractions of selected cultivated soils, but no phosphate minerals were detected in any fraction of the corresponding native soils. Soils were also incubated under field capacity moisture content for 30days, either without P application or with 66.8mgPkg−1 soil applied as KH2PO4. Soil solutions were extracted and the concentrations of both anions and cations were determined. The activities of Ca2+ and H2PO4− calculated using the MINTEQA2 speciation program were adequate to support the stability of hydroxyapatite (HA), fluorapatite (FA) and tricalcium phosphate (TCP) minerals in farmed soils, while TCP was unstable in unfarmed soils, and the solution points of TCP were close to the equilibrium of HA. The results indicated that phosphate activities in native and heavily fertilized calcareous soils were controlled by the solubility of different phosphate minerals. Sequential fractionation data suggested that Ca–Mg-associated P accounted for a dominant proportion of total P in farmed soils, but this fraction was below the detectable limit in unfarmed soils. These findings demonstrate that the repeated heavy application of phosphate fertilizer during many years has resulted in the formation of stable, crystalline calcium phosphate minerals in these farmed calcareous soils.

Evaluation of Soil Physical Quality under Amendments and Hydrogel Applications in a Soybean–Wheat Cropping System

A field study was conducted in alluvial sandy loam soil to assess the impact of amendments and hydrogel application on soil hydrophysical properties. Soil physical environment was characterized and quantified using soil physical quality index (S). The main treatments include farmyard manure (FYM) and tank soil applied at 5 t ha−1 and no amendment, and subtreatments included three rates of hydrogel: 5, 2.5, and 0 kg ha−1. Hydrogel was applied at 5–7 cm deep just below the seed in rows. Results revealed that FYM along with gel application at 5 kg ha−1 significantly increased mean weight diameter, field capacity moisture content, plant-available water content and relative field capacity, retention pores (Ret P), water-stable structural units, and structural coefficient and reduced transmission pores (TP), penetration resistance, and saturated hydraulic conductivity (Ks). Significantly greater values of S in hydrogel-treated plots and close associations of S with other soil physical parameters were obtained.

Nitrous oxide emissions from Chernozemic soils amended with anaerobically digested beef cattle feedlot manure: A laboratory study

Biogas production from beef cattle (Bos taurus) feedlot manure results in co-generation of anaerobically digested manure (ADM), a nutrient rich substrate with a solid fraction (SS) often applied to cropland. Application of SS to cropland may result in lower N2O emissions than raw manure due to biochemical changes occurring during anaerobic digestion. We tested this hypothesis using a laboratory incubation study in which N2O fluxes from two Alberta soils, being a Dark Brown Chernozem clay loam (Typic Haploboroll) and a Black Chernozem silty clay (Typic Haplocryoll) amended with raw beef cattle feedlot manure, SS, pelletized SS (PSS), and urea+monoammonium phosphate (UMP) were measured over 10weeks. Amendments were applied at rates corresponding to 100 and 200kgN/ha, with a 0N control included for comparison. Amended soils were maintained near 70% of field capacity moisture content and incubated for 10weeks at 22°C. Gas samples were collected 0, 3 and 7days after the start of the incubation and weekly thereafter for N2O and CO2 analysis by gas chromatography. The N2O fluxes differed among amendments with the differences dependent on soil, amendment application rate, and time. Across amendment rates, mean cumulative emissions from SS- (2.38mgN/kg) and UMP amended soils (0.59mgN/kg) did not differ, but were both lower than emissions from PSS amended soils (10.7mgN/kg) and those from the higher manure rate (15.6mgN/kg). The high N2O emissions from PSS amended soils were likely due to the concentrated microsites of N in pellets. A difference in cumulative N2O emissions between PSS and SS only occurred in Black Chernozem. Microbial activity as indicated by cumulative CO2 fluxes was highest in SS amended (6.7gCO2-C/kg) and lowest in UMP amended soils (0.14gCO2-C/kg). Post-incubation net mineral N content was highest in manure amended soils (144mgN/kg), marginal in SS amended soils (23mgN/kg), and lowest in PSS amended soils that had net N immobilization (−67mgN/kg) due to low available N content in the pellets. Results suggest that field application of SS may reduce N2O emissions relative to raw manure.This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.

A comparison of soil and water properties in organic and conventional farming systems in England

AbstractOrganic farming and improvements to agricultural sustainability are often seen as synonymous. However, an extensive European review demonstrated that in practice this is not always true. This study aims to compare the status of soil and water properties between separate fields managed in either an organic or a conventional manner. Soil samples were collected from 16 pairs of farms, throughout England, with both arable and grass fields within each pair on similar soil type. Chemical (nutrients, pesticides, herbicides) and physical (aggregate stability, field capacity, shear strength, soil organic matter, infiltration rates) soil properties were measured in four main soil texture classes in organic and conventional fields. The physical soil properties varied significantly between the different classes of texture and land use. The heavier textured soils have significantly higher soil organic carbon (SOC), aggregate stability and shear strength. The coarse‐textured soils have significantly lower field capacity moisture contents. The grassland has a significantly higher level of SOC, field capacity moisture content, aggregate stability and soil shear strength. However, there were no significant differences between organic and conventional treatments for any of the soil physical properties measured. There were fewer traces of agrochemicals in the soil water from the organic fields compared with the conventionally managed fields. The conventional arable fields had higher levels of total inorganic nitrogen than the other land uses and treatments. There was evidence to show that infiltration rates were significantly higher on organically managed grassland soils (7.6 mm/h) than conventionally managed grassland (2.5 mm/h) with lower stocking rates. The results suggest that improved grassland management, whether organic or conventional, could reduce predicted runoff by 28%.

Effects of soil conditioners on physical quality and bromide transport properties in a sandy loam soil

In coarse-textured soils, water and nutrients are lost from the root zone through deep percolation and preferential flow, resulting in poor soil quality. The objective of this study was to investigate the influences of polyacrylamide, cattle manure, vermicompost and biological sludge as soil conditioners on moisture retention and bromide transport parameters in a sandy loam soil. Polyacrylamide (0.25 and 0.5 g kg−1 of air-dried soil), cattle manure (12.5 and 25 g kg−1 of air-dried soil), vermicompost (2.5 and 5 g kg−1 of air-dried soil) and biological sludge (1.7 and 3.4 g kg−1 of air-dried soil) were mixed with the soil and uniformly packed into plastic pans and PVC columns, and incubated in a greenhouse at 0.7 to 0.8 field capacity moisture content (0.143–0.163 g g−1) and at 22 ± 4 °C for 6 months. Pans were used to take core samples to determine soil moisture curve parameters at 7, 30, 60, 120, and 180 days. Bromide breakthrough curves were measured at the same time in the PVC columns. Polyacrylamide significantly increased slope of soil moisture curve at its inflection point as compared to the control and other soil conditioners. Polyacrylamide also prevented early breakthrough of bromide at 7 days by decreasing saturated hydraulic conductivity, compared to the control and biological sludge. All soil conditioners reduced dispersivity parameter in convection–dispersion model. Significant (P ≤ 0.01) positive correlation (r = 0.81) was found between dispersivity parameter in convection–dispersion and mobile–immobile models at the five incubation times. The results showed that polyacrylamide was more effective than other soil conditioners in improving physical quality of sandy loam soils.

Humic Substances Generally Ineffective in Improving Vegetable Crop Nutrient Uptake or Productivity

Soil application of humic acid (HA), generally derived from leonardite shale, is a common practice in California vegetable production. Five commercial HA formulations were evaluated for their effects on soil microbial activity, seedling emergence, crop productivity, and nutrient uptake when applied to representative agricultural soils. Two soils differing in organic matter content (8 and 25 g·kg−1) were wetted to field capacity moisture content with solutions of water, nitrogen and phosphorus (P) fertilizer, HA, or fertilizer + HA and incubated aerobically at 25 °C. In the lower organic matter soil, a synergistic effect of fertilizer and HA was observed after 7 days of incubation on both microbial respiration and the amount of phospholipid fatty acids detected; these stimulatory effects were not observed in the higher organic matter soil. In a greenhouse pot study, the effects of HA on seedling emergence, dry mass accumulation, and P uptake of romaine lettuce (Lactuca sativae L.) were evaluated in four soils of low P availability; HA was applied to the soil at a rate simulating a field application of 2.2 kg·ha−1 a.i. HA had no significant effect on emergence rate or percentage, or P uptake, in any soil; plant dry mass was increased in one soil. Field trials were conducted in 2008 and 2009 evaluating the effects of pre-transplant soil application of HA at 1.1 or 3.4 kg·ha−1 a.i. on growth, nutrient uptake, and fruit yield of processing tomato (Lycopersicon esculentum Mill.). In neither year was macro- or micronutrient uptake increased with HA. Similarly, there was no significant HA effect on plant dry mass accumulation or fruit yield. We conclude that, at typical commercial application rates in representative field soils, HA is unlikely to significantly improve vegetable crop nutrient uptake or productivity.

Plant Available Moisture in Stone-soil Media for Use Under Pavement While Allowing Urban Tree Root Growth

Three avenues of experimental observation detail aspects of plant available water holding capacity in compacted stone-soil media designed for urban tree establishment in paved situations. The various compacted media provided an estimated plant available moisture content of 7%–11% by volume, comparable to a loamy sand. Changes in aggregate and of soil influenced initial field capacity moisture content, but high matric potential moisture content was consistent, presumably as a reflection of the aggregate content of the designed system. A large portion of plant available moisture was weakly held in large voids, consistent with related infiltration and permeability data, and could be an influence in water storage and irrigation planning to use layers of designed soils in a layered pavement section for urban vegetation.

Influence of dicyandiamide on nitrogen transformation and losses in cow-urine-amended soil cores from grazed pasture

In New Zealand, urine deposited by grazing animals represents the largest source of nitrogen (N) losses, as gaseous emissions of ammonia (NH3) and nitrous oxide (N2O), and leaching of nitrate (NO3−).We determined the effect of dicyandiamide (DCD) on gaseous emissions from pasture with increasing rates of urine-N application, mineral N transformations and potential leaching of N using undisturbed soil cores of Manawatu sandy loam at field capacity. The treatments included four levels of urine-N applied at 0 (control), 14.4, 29.0 and 57.0 g N/m2 with and without DCD at 2.5 g/m2. Results showed a significant (P &lt; 0.05) increase in NH3 and N2O-N emissions as urine application was increased. The addition of DCD to corresponding urine treatments reduced N2O emissions by 33, 56 and 80%, respectively. The addition of DCD with urine to the intact soil cores at field capacity moisture content resulted in a significant increase in the soil ammonium-N (NH4+-N) concentration but little change in NH3 emissions. Addition of DCD to urine reduced potential NO3−-N leaching by 60–65% but potential NH4+-N leaching increased by 2–3.5 times. There was no difference in pasture dry matter production with and without DCD treatments.

Soil Calcium Status Unrelated to Tipburn of Romaine Lettuce

Application of calcium (Ca) fertilizers is a common practice of California lettuce growers to minimize the occurrence and severity of tipburn, particularly in romaine lettuce (Lactuca sativa L. var. longifolia Lam.). An evaluation of the effect of soil Ca availability on the severity of tipburn in romaine lettuce was conducted in the Salinas Valley of central California in 2005 to 2006. Twenty representative soils from this region were evaluated for Ca availability by ammonium acetate extraction, saturated paste extraction, and extraction of soil solution through centrifugation of soil at field-capacity moisture content. Soil solution Ca in these soils was generally high, ranging from 5 to 80 mmolc·L−1, representing 44% to 71% of cations on a charge basis. Soil solution Ca was highly correlated with saturated paste Ca (r 2 = 0.70) but not with exchangeable Ca (r 2 = 0.01). However, saturated paste extraction significantly underestimated soil solution Ca concentration (regression slope = 0.19). A survey of 15 commercial romaine lettuce fields showed tipburn severity to be unrelated to either leaf Ca concentration or soil Ca availability. The most severe tipburn was observed in fields in which transpiration was reduced by foggy weather during the final 2 weeks of growth. Ca fertilizers (calcium nitrate, calcium thiosulfate, and calcium chloride) applied through drip irrigation during the final weeks of lettuce growth were ineffective in increasing romaine leaf Ca concentration in three field trials; tipburn was present in only one trial, and Ca fertigation had no effect on tipburn severity. We conclude that under typical field conditions in this region, tipburn severity is primarily a function of environmental conditions. Soil Ca availability plays no substantive role in tipburn severity, and Ca fertigation does not improve lettuce Ca uptake or reduce tipburn.

Factors Affecting Change in Soil Test Phosphorus Following Manure and Fertilizer Application

In many states, Morgan (M) or Mehlich‐3 (M3) extractions are the basis for P fertility recommendations and P runoff risk assessment. The impact of timing of sampling, P source, and extractable Al on agronomic soil test P (STP) and P release to the environment are not well understood. Incubation studies were conducted to determine: (i) changes in M‐P, M3‐P, and 0.01 M CaCl2–P with time following Ca(H2PO4)2 addition; (ii) the efficiency of liquid dairy manure, NH4HPO4, and Ca(H2PO4)2 in raising M‐P and M3‐P levels; and (iii) the degree to which initial P and extractable Al impact the efficiency of applied P. Twenty‐eight noncalcareous soils were incubated at 23°C, in the dark, at field capacity moisture content. Extractable P decreased over 60 d, with a greater proportion of P being lost from the more labile pools (CaCl2–P &gt; M‐P &gt; M3‐P). The increase in STP per unit P added (ΔP‐M and ΔP‐M3) was affected by P source: NH4HPO4 raised P levels more efficiently than Ca(H2PO4)2 or liquid dairy manure. There was a positive linear relationship between ΔP and initial STP. Extractable Al was inversely related to ΔP‐M and ΔP‐M3 and followed exponential decay functions. Extractable Al was positively and linearly related to the amount of P required to raise M‐P and M3‐P levels 1 mg kg−1, with Morgan Al as the most accurate predictor of ΔP. Our results suggest that the New York P index should include guidance on sampling time and account for the higher P sorption capacity of soils inherently high in extractable Al.