Crop production impacts on soil phosphorus removal and soil test levels

An 8-year field study documented the impact of tillage, crop rotations, and crop residue management on agronomic and soil parameters at Brookings, South Dakota. The greatest annual proportion of above-ground biomass phosphorus (P) removed was from the grain (78–87% of total) although crop residue removed some P as well. Greater above-ground total biomass P (grain P + crop residue P) was removed from corn than from soybean and spring wheat crops mainly due to the greater corn grain biomass harvested. Cumulative above-ground biomass P removal was greatest for the corn-soybean rotation (214 kg P ha^?1), while it was lowest for the soybean-wheat rotation (157 kg P ha^?1). Tillage treatments within crop rotation or residue management treatments did not influence annual or cumulative P removal rates. Olsen extractable soil orthophosphate-P levels declined consistently through time from a mean of 40 µg g^?1 (2004) to 26 µg g^?1 (2011). Biomass P removal was calculated to be 15.7 ha^?1 yr^?1 to decrease Olsen extractable soil orthophosphate-P levels by 1 µg g^?1 yr^?1 over 8 years of the study.     

Effect of soybean inoculation with Bradyrhizobium and wheat inoculation with Azotobacter on their productivity and N turnover in a Vertisol

A long-term field experiment was conducted for 8 years on a Vertisol in central India to assess quantitatively the direct and residual N effects of soybean inoculation with Bradyrhizobium and wheat inoculation with Azotobacter in a soybean–wheat rotation. After cultivation of soybean each year, its aerial residues were removed before growing wheat in the same plots using four N levels (120, 90, 60 and 30 kg ha^?1) and Azotobacter inoculation. Inoculation of soybean increased grain yield by 10.1% (180 kg ha^?1), but the increase in wheat yields with inoculation was only marginal (5.6%; 278 kg ha^?1). There was always a positive balance of soil N after soybean harvest; an average of +28 kg N ha^?1 yr^?1 in control (nodulated by native rhizobia) plots compared with +41 kg N ha^?1 yr^?1 in Rhizobium-inoculated plots. Residual and direct effects of Rhizobium and Azotobacter inoculants caused a fertilizer N credit of 30 kg ha^?1 in wheat. Application of fertilizers or microbial inoculation favoured the proliferation of rhizobia in crop rhizosphere due to better plant growth. Additional N uptake by inoculation was 14.9 kg N ha^?1 by soybean and 20.9 kg N ha^?1 by wheat crop, and a gain of +38.0 kg N ha^?1 yr^?1 to the 0–15 cm soil layer was measured after harvest of wheat. So, total N contribution to crops and soil due to the inoculants was 73.8 kg N ha^?1 yr^?1 after one soybean–wheat rotation. There was a total N benefit of 13.8 kg N ha^?1 yr^?1 to the soil due to regular long-term use of microbial inoculants in soybean–wheat rotation.     

Soil Physical Properties and Organic Matter Fractions Under Forages Receiving Composts,Manure or Fertilizer

A field study was conducted to assess the benefits, with respect to soil physical properties and soil organic matter fractions of utilizing composts from a diversity of sources in perennial forage production. A mixed forage (timothy-red clover (Trifolium pratense L.) and monocrop timothy (Phleum pratense L.) sward were fertilized annually with ammonium nitrate (AN) at up to 150kg and 300 N ha^?1 yr^?1, respectively, from 1998-2001. Organic amendments, applied at up to 600 kg N ha^?1 yr^?1 in the first two years only, included composts derived from crop residue (CSC), dairy manure (DMC) or sewage sludge (SSLC), plus liquid dairy manure (DM), and supplied C to soil at 4.6 and 9.2 (CSC), 10.9 (SSLC), 10.0 (DMC) 2.9 (DM) Mg C ha^?1. Soil samples (0-5cm; 5-10cm;10-15cm) were recovered in 2000 and 2001. Improvements in soil physical properties (soil bulk density and water content) were obtained for compost treatments alone. Composts alone influenced soil C:N ratio and substantially increased soil organic carbon (SOC) concentration and mass (+ 5.2 to + 9.7 Mg C ha^?1). Gains in SOC with AN of 2.7 Mg C ha^?1 were detectable by the third crop production year (2001). The lower C inputs, and more labile C, supplied by manure (DM) was reflected in reduced SOC gains (+ 2.5 Mg C ha^?1) compared to composts. The distribution of C in densiometric (light fraction, LF; >1.7 g cm^?3) and particulate organic matter (POM; litter (>2000μm); coarse-sand (250-2000μm); fine-sand (53-250μm) fractions varied with compost and combining fractionation by size and density improved interpretation of compost dynamics in soil. Combined POM accounted for 82.6% of SOC gains with composts. Estimated compost turnover rates (k) ranged from 0.06 (CSC) to 0.09 yr^?1 (DMC). Composts alone increased soil microbial biomass carbon (SMB-C) concentration (μg C g^?1 soil). Soil available C (C_ext) decreased significantly as compost maturity increased. For some composts (CSC), timothy yields matched those obtained with AN, and SOC gains were derived from both applied-C and increased crop residue-C returns to soil. A trend towards improved C returns across all treatments was apparent for the mixed crop. Matching composts of varying quality with the appropriate (legume/nonlegume) target crop will be critical to promoting soil C gains from compost use.     

Nitrogen Balance in the Magruder Plots Following 109 Years in Continuous Winter Wheat

Abstract

The Magruder plots are the oldest continuous soil fertility wheat research plots in the Great Plains region, and are one of the oldest continuous soil fertility wheat plots in the world. They were initiated in 1892 by Alexander C. Magruder who was interested in the productivity of native prairie soils when sown continuously to winter wheat. This study reports on a simple estimate of nitrogen (N) balance in the Magruder plots, accounting for N applied, N removed in the grain, plant N loss, denitrification, non‐symbiotic N fixation, nitrate (NO₃ ^?) leaching, N applied in the rainfall, estimated total soil N (0–30 cm) at the beginning of the experiment and that measured in 2001. In the Manure plots, total soil N decreased from 6890 kg N ha^?1 in the surface 0–30 cm in 1892, to 3198 kg N ha^?1 in 2002. In the Check plots (no nutrients applied for 109 years) only 2411 kg N ha^?1 or 35% of the original total soil organic N remains. Nitrogen removed in the grain averaged 38.4 kg N ha^?1 yr^?1 and N additions (manure, N in rainfall, N via symbiotic N fixation) averaged 44.5 kg N ha^?1 yr^?1 in the Manure plots. Following 109 years, unaccounted N ranged from 229 to 1395 kg N ha^?1. On a by year basis, this would translate into 2–13 kg N ha^?1 yr^?1 that were unaccounted for, increasing with increased N application. For the Manure plots, the estimate of nitrogen use efficiency (NUE) (N removed in the grain, minus N removed in the grain of the Check plots, divided by the rate of N applied) was 32.8%, similar to the 33% NUE for world cereal production reported in 1999.     

Catch Crop and Animal Slurry in Spring Barley Grown with Straw Incorporation

Abstract

Four rates of straw (0, 4, 8 and 12 t ha^?1 yr^?1) were incorporated in a field experiment with continuous spring barley. The experiment was conducted on a sandy soil (5.5% clay) and a sandy loam soil (11.2% clay). After eight years, the straw incorporation was combined with catch-crop growing with and without winter application of animal slurry and also spring fertilization with mineral fertilizer (0, 50, 100 or 125 kg N ha^?1 yr^?1). The combined experiment was conducted for three lyears on the sandy soil and for four years on the sandy loam soil. The effects on barley dry matter yield and N uptake are presented together with the long-term effects of the straw incorporations on crop growth and soil C and N. Grain yield on the sandy loam was unaffected by straw incorporation. On the sandy soil the highest straw application rates reduced grain yield in the unfertilized barley. When the barley received mineral fertilizer at recommended levels (100 kg N ha^?1 yr^?1), grain yield on this soil was also unaffected by the high straw rates. Including a catch crop had a positive effect on the grain yield of barley on both soils. The total N uptake in grain and straw generally increased with straw application up to 8 t ha^?1 yr^?1. With the highest straw application rate (12 t ha^?1 yr^?1), the total N uptake decreased but still exceeded N uptake in barley grown with straw removal. The barley accumulated higher amounts of N when a catch crop was included. The total N uptake in the barley was significantly higher after animal slurry application. The extra N uptake, however, was much lower than the amounts of N applied with the slurry. Incorporation of straw had only a small influence on N uptake after slurry application. The straw, therefore, was not able to store the applied N during winter. In the two four-year periods before the combined experiment, grain yield on the sandy loam was generally negatively affected by straw incorporations. In the second period, N uptake began to show a positive effect of the straw. On the sandy soil, grain yield and N uptake during the whole period were generally positively affected by the straw incorporations except for the highest straw rate (12 t ha^?1 yr^?1). The sandy loam soil showed higher increases in C and N content after the repeated straw incorporations and catch-crop growing than the sandy soil. When application of animal slurry was combined with the catch crop, no further increases in soil C and N were found relative to soil where a catch crop was grown without slurry application. Large amounts of the N applied with the slurry may therefore have been lost by denitrification or nitrate leaching.     

Filling the European blank spot—Swiss soil erodibility assessment with topsoil samples

Soil erodibility, commonly expressed as the K‐factor in USLE‐type erosion models, is a crucial parameter for determining soil loss rates. However, a national soil erodibility map based on measured soil properties did so far not exist for Switzerland. As an EU non‐member state, Switzerland was not included in previous soil mapping programs such as the Land Use/Cover Area frame Survey (LUCAS). However, in 2015 Switzerland joined the LUCAS soil sampling program and extended the topsoil sampling to mountainous regions higher 1500 m asl for the first time in Europe. Based on this soil property dataset we developed a K‐factor map for Switzerland to close the gap in soil erodibility mapping in Central Europe. The K‐factor calculation is based on a nomograph that relates soil erodibility to data of soil texture, organic matter content, soil structure, and permeability. We used 160 Swiss LUCAS topsoil samples below 1500 m asl and added in an additional campaign 39 samples above 1500 m asl. In order to allow for a smooth interpolation in context of the neighboring regions, additional 1638 LUCAS samples of adjacent countries were considered. Point calculations of K‐factors were spatially interpolated by Cubist Regression and Multilevel B‐Splines. Environmental features (vegetation index, reflectance data, terrain, and location features) that explain the spatial distribution of soil erodibility were included as covariates. The Cubist Regression approach performed well with an RMSE of 0.0048 t ha h ha^?1 MJ^?1 mm^?1. Mean soil erodibility for Switzerland was calculated as 0.0327 t ha h ha^?1 MJ^?1 mm^?1 with a standard deviation of 0.0044 t ha h ha^?1 MJ^?1 mm^?1. The incorporation of stone cover reduces soil erodibility by 8.2%. The proposed Swiss erodibility map based on measured soil data including mountain soils was compared to an extrapolated map without measured soil data, the latter overestimating erodibility in mountain regions (by 6.3%) and underestimating in valleys (by 2.5%). The K‐factor map is of high relevance not only for the soil erosion risk of Switzerland with a particular emphasis on the mountainous regions but also has an intrinsic value of its own for specific land use decisions, soil and land suitability and soil protection.     

An evaluation of the pesera soil erosion model and its application to a case study in Zakynthos, Greece

Abstract. The Pan‐European Soil Erosion Risk Assessment (pesera ) model was evaluated using existing soil erosion data collected under various types of climate, vegetation, landscape and soil conditions. The data used represent a variety of typical Mediterranean land uses such as winter wheat, vines, olives and bare, stony land prevailing in hilly areas. Using this data, the model was calibrated for sediment transport by overland flow and results compared to measured soil erosion values from runoff plots and a watershed on a monthly basis. The performance of the model was assessed statistically, showing that it can be satisfactorily used for predicting soil erosion rates under the conditions included in the study. The overall model estimate including all the available experimental data was 0.69 t ha^?1 yr^?1 with a maximum error of 1.49 t ha^?1 yr^?1. After validation, the model was applied to a small watershed (60 ha) of great ecological importance for the sea turtle Caretta caretta. For this purpose, soil and vegetation maps were compiled from all the necessary data for applying the model. The model was run for three years using daily data from an existing nearby meteorological station. The predicted and measured soil erosion rates for a 7‐month period were 0.31 t and 0.18 t, respectively. Application of the model to each mapping unit showed the over‐riding importance of land use for sediment generation under the given climatic conditions. Bare land, occupying 5.5% of the watershed area, generated up to 69% of the total sediments estimated for the watershed. It is concluded that the pesera model can be used as a regional diagnostic tool under a range of soil, topographic and climatic conditions for identifying the best land use type and vegetation cover to protect hilly areas from soil erosion. The calculated overall root mean square error for the model is 0.06 t ha^?1 yr^?1, compared to a soil erosion rate of 0.04 t ha^?1 yr^?1, which can be tolerated for protecting the area for the sea turtle.     

Long-term nitrogen balance for pearl millet (Pennisetum glaucum L.) in an acid sandy soil of Niger

On acid sandy soils of Niger (West Africa) fertilizer N recovery by pearl millet (Pennisetum glaucum L.) is often more than 100 per cent in years with normal or above average rainfall. Biological nitrogen fixation (BNF) by N₂-fixing bacteria may contribute to the N supply in pearl millet cropping systems. For a long-term field experiment comprising treatments with and without mineral fertilizer (F) and with and without crop residue application (CR) a N balance sheet was calculated over a period of six years (1983-1988). After six years of successive millet cropping total N uptake (36-77 kg N ha^?1 yr^?1) was distinctly higher than the amount of fertilizer N applied (30 kg N ha^?1 yr^?1). The atmospheric input of NH₄-N and NO₃-N in the rainwater was about 2 kg N ha_?1 yr^?1, 70 % in the form of NH₄-N. Gaseous NH₃ losses from urea (broadcast, incorporated) were estimated from other experiments to amount to 36 % of the fertilizer N applied. Nitrogen losses by leaching (15 to > 25 kg N ha^?1 yr^?1) were dependent on the treatment and on the quantity and distribution of single rainfall events (>50 mm). Decline in total soil N content (0-60 cm) ranged from 15 to 48 kg N ha^?1 yr^?1. The long-term N balance (1983-1988) indicated an annual net gain between 6 (+CR-F) and 13 (+CR+F) kg N ha^?1 yr^?1. For the control (-CR-F) the long-term N balance was negative (10 kg N ha^?1 yr^?1). In the treatment with crop residues only, the N balance was mainly determined by leaching losses, whereas in treatments with mineral fertilizer application the N balance depended primarily on N removal by the millet crop. The annual net gain in the N balance increased from 7 kg ha^?1 with mineral fertilizer to 13 kg ha^?1 in the combination mineral fertilizer plus crop residues. In both the rhizosphere and the bulk soil (0-15 cm), between 9 and 45% of the total bacterial population were N₂-fixing (diazotrophic) bacteria. The increased N gain upon crop residue application was positively correlated with an increase in the number of diazotrophic and total bacteria. The data on bacterial numbers suggest that the gain of N in the longterm N balance is most likely due to an N input by biological nitrogen fixation. In addition, evidence exists from related studies that the proliferation of diazotrophs and total bacteria in the rhizosphere due to crop residue application stimulated root growth of pearl millet, and thus improved the phosphorus (P) acquisition in the P deficient soil.     

Nutrient fluxes from a soil treatment process for pig slurry

Abstract. The effects of pig slurry applications to a hydrologically isolated field treatment plant (at Solepur) were studied over a period of eight years. Thirty repeated doses, averaging 160 m³ ha^?1 were applied from April to October of each year (1991–1995), to reach a total application of 4930 m³ ha^?1. All slurry samples were analysed for their total solids (TS), macronutrient (C, N, P, K, Ca) and micronutrient (Cu, Zn) content. In total, 284 tonnes of total solids (57 t TS ha^?1 yr^?1), 115 tonnes of carbon (23 t C ha^?1yr^?1), 24.5 tonnes of nitrogen (4900 kg N ha^?1 yr^?1), 7964 kg of phosphorus (1593 kg P ha^?1 yr^?1), 16 518 kg of potassium (3304 kg K ha^?1 yr^?1), 183 kg copper (37 kg Cu ha^?1 yr^?1) and 266 kg zinc (53 kg Zn ha^?1 yr^?1) were applied to the soil. Thus, this site provides an opportunity to assess the balance and to examine the long‐term behaviour of nutrients under conditions of intensive land application of pig slurries or similar effluents. The main nutrient fluxes through the soil‐water system were determined for each element. Over 40% of the total carbon applied was retained by the soil. About 25% of the slurry nitrogen applied remained in the soil profile and 12.5% was leached through the drainage water as nitrate. Most of the slurry phosphorus applied was retained in the soil profile either as P‐Dyer extractable (83%), or as total soil phosphorus (112%); <0.01% was found in the drainage water. Forty‐three per cent of the potassium applied in the slurry was recovered from the soil profile and 15% was recovered in the drainage water. Most of the copper (62%) and zinc (74%) applied in the slurry remained in the soil as EDTA extractractable forms; very low percentages (0.05% and 0.6% respectively) were found in the drainage water.     

Proton Budget for a Japanese Cedar Forest Ecosystem

The proton budget for a Japanese cedar (Cryptomeria japonica) forest in Gunma Prefecture, Japan, was studied by estimating biogeochemical fluxes. The proton budgets were estimated for three individual compartments of the ecosystem: vegetation canopy, and the upper (O horizon + 0–10 cm) and lower (10–100 cm) soil layers. The dominant proton sources in the compartments were atmospheric deposition (1.2 kmol ha^?1 yr^?1), nitrification (5.1 kmol, ha^?1 yr^?1) and base-cation uptake by vegetation (8.0 kmol, ha^?1 yr^?1) respectively. These proton sources were neutralized almost completely within the individual compartments mainly by base-cation release from the canopy or the soil. The sum of internal proton sources was five times as large as that of external ones. Nitrogen input from the atmosphere was 2.2 kmol ha^?1 yr^?1, whereas its output from the lower soil layer was 3.9 kmol ha^?1 yr^?1, indicating that a net loss of nitrogen occurred in the ecosystem. However, this did not cause the acidification of soil leachates because of a sufficient release rate of base cations from the soil.     

Nitrate leaching loss under annual and perennial pastures with and without lime on a duplex (texture contrast) soil in humid southeastern Australia

Mineral N accumulates in autumn under pastures in southeastern Australia and is at risk of leaching as nitrate during winter. Nitrate leaching loss and soil mineral N concentrations were measured under pastures grazed by sheep on a duplex (texture contrast) soil in southern New South Wales from 1994 to 1996. Legume (Trifolium subterraneum)‐based pastures contained either annual grass (Lolium rigidum) or perennial grasses (Phalaris aquatica and Dactylis glomerata), and had a control (soil pH 4.1 in 0.01 m CaCl₂) or lime treatment (pH 5.5). One of the four replicates was monitored for surface runoff and subsurface flow (the top of the B horizon), and solution NO₃^– concentrations. The soil contained more mineral N in autumn (64–133 kg N ha^?1 to 120 cm) than in spring (51–96 kg N ha^?1), with NO₃^– comprising 70–77%. No NO₃^– leached in 1994 (475 mm rainfall). In 1995 (697 mm rainfall) and 1996 (666 mm rainfall), the solution at 20 cm depth and subsurface flow contained 20–50 mg N l^?1 as NO₃^– initially but < 1 mg N l^?1 by spring. Nitrate‐N concentrations at 120 cm ranged between 2 and 22 mg N l^?1 during winter. Losses of NO₃^– were small in surface runoff (0–2 kg N ha^?1 year^?1). In 1995, 9–19 kg N ha^?1 was lost in subsurface flow. Deep drainage losses were 3–12 kg N ha^?1 in 1995 and 4–10 kg N ha^?1 in 1996, with the most loss occurring under limed annual pasture. Averaged over 3 years, N losses were 9 and 15 kg N ha^?1 year^?1 under control and limed annual pastures, respectively, and 6 and 8 kg N ha^?1 year^?1 under control and limed perennial pastures. Nitrate losses in the wet year of 1995 were 22, 33, 13 and 19 kg N ha^?1 under the four respective pastures. The increased loss of N caused by liming was of a similar amount to the decreased N loss by maintaining perennial pasture as distinct from an annual pasture.     

Phosphorus balances for arable soils in Southern England 1986–1999

The behaviour of P in a range of English arable soils was examined by plotting the change in resin P in the topsoil (ΔPres) at the end of a 3‐ to 5‐year period, against the P balance over the same period (fertilizer P applied minus offtake in crops, estimated from farmers’ reported yields and straw removal). Based on the assumption that values for offtake per tonne of crop yield used for UK arable crops are valid averages, 20–60% of ΔPres was explained by the balance. Applying excess P fertilizer increased Pres, and reducing P fertilizer use decreased it; typically 3–4 kg P ha^?1 was required for each mg L^?1ΔPres (6–8 kg ha^?1 for each mg L^?1 of Olsen P). About half the P balance seems to be resin extractable and this differed little between soil groups, except in cases of very low P (index 0) in which the P buffering was stronger, and on very high P soils (index 4/5) when buffering was less. However, on calcareous soils and red soils, when fertilizer was applied in accord with offtake, Pres fell by up to 4 mg L^?1 year^?1 (2 mg L^?1 yr^?1 olsen P) and to prevent this an extra 3–10 kg P ha^?1 year^?1 fertilizer was required. But on most non‐calcareous soils, replacing offtake maintained Pres, with perhaps slight rises on soils of low clay content or greater organic matter content. In soils under arable rotations, the apparent recovery of P from fertilizer was often around 100%, falling to 85% on Chalk soils and 75% on medium–heavy soils on limestone or Lower Chalk. The fate of the ‘missing’ P needs clarification. The case for corrections to current P fertilizer recommendations in the UK on certain soil types is discussed.     

Effects of land management on CO2 flux and soil C stock in two Tanzanian croplands with contrasting soil texture

Evaluation of carbon dynamics is of great concern worldwide in terms of climate change and soil fertility. However, the annual CO₂ flux and the effect of land management on the carbon budget are poorly understood in Sub-Saharan Africa, owing to the relative dearth of data for in situ CO₂ fluxes. Here, we evaluated seasonal variations in CO₂ efflux rate with hourly climate data in two dry tropical croplands in Tanzania at two sites with contrasting soil textures, viz. clayey or sandy, over four consecutive crop-cultivation periods of 40 months. We then: (1) estimated the annual CO₂ flux, and (2) evaluated the effect of land management (control plot, plant residue treatment plot, fertilizer treatment plot, and plant residue and fertilizer treatment plot) on the CO₂ flux and soil carbon stock at both sites. Estimated annual CO₂ fluxes were 1.0–2.2 and 0.9–1.9 Mg C ha^?1 yr^?1 for the clayey and sandy sites, respectively. At the end of the experiment, crop cultivation had decreased the surface soil carbon stocks by 2.4 and 3.0 Mg C ha^?1 (soil depth 0–15 cm) at the clayey and sandy sites, respectively. On the other hand, plant residue application (7.5 Mg C ha^?1 yr^?1) significantly increased the surface soil carbon stocks, i.e., 3.5–3.8 and 1.7–2.1 Mg C ha^?1 (soil depth 0–15 cm) at the clayey and sandy sites, respectively, while it also increased the annual CO₂ fluxes substantially, i.e., 2.5–4.0 and 2.4–3.4 Mg C ha^?1 yr^?1 for the clayey and sandy soils, respectively. Our results indicate that these dry tropical croplands at least may act as a carbon sink, though the efficiency of carbon accumulation was substantially lower in sandy soil (6.8–8.4%) compared to clayey soil (14.0–15.2%), possibly owing to higher carbon loss by leaching and macro-faunal activity.     

Soil conservation on road embankments using palm‐mat geotextiles: field studies in Lithuania

The application of geotextile mats constructed from the palm leaves of Borassus aethiopum (Borassus) and Mauritia flexuosa (Buriti) was investigated in field experiments. The use of geotextiles caused improved soil moisture storage during dry summer periods on a steep (21–25°) roadside slope in Lithuania. The enhanced soil moisture under the Borassus and Buriti mats encouraged better root development of perennial grasses, increased the number and weight of earthworms and increased the dry biomass of perennial grasses by 50.5 and 18.2%, respectively, compared with a grassland control. The mean rate of water erosion from bare soil during the study period from 17/04/2007 to 11/12/2008 was 33.21 Mg/ha. The cover of palm‐mat geotextiles decreased soil losses from bare fallow soil by 94.8–91.1%. An erosion rate of 0.85 Mg/ha over this 21‐month period was measured on the slope under perennial grasses without geotextile cover. Application of geotextile cover on perennial grasses completely prevented soil erosion by water. Therefore, use of geotextiles has clear soil and water conservation benefits on industrial slopes susceptible to erosion. The use of geotextiles has multiple benefits including soil conservation, the improvement of plant growth conditions and the encouragement of earthworm populations.     

Yard Trimmings as a Source of Nitrogen for Crop Production

Yard trimmings from sources rich in grass clippings have the potential to supply nutrients for crop production. Our objectives were to estimate N availability from yard trimmings and determine their effects on crop production, soil nutrients, and organic matter levels. We conducted a field experiment, comparing three consecutive years of yard trimmings applications (22, 44, or 66 Mg ha^?1 yr^?1 dry weight) with inorganic N (112 kg N ha^?1 yr^?1) and zero-N controls in a silage corn (Zea mays L.) - winter triticale (Triticosecale spp.) rotation. The yard trimmings were screened and ground, and allowed to heat for a short period. They were incorporated each spring before planting corn. We measured crop yield and N uptake, and estimated apparent N recovery (ANR). We measured soil inorganic N two weeks after yard trimmings application and after corn harvest. In a one-year on-farm demonstration, we compared three sources of yard trimmings applied at a single rate. Yard trimmings applied at 44 Mg ha^?1 dry weight provided sufficient available N to replace inorganic N. For silage corn grown with summer irrigation, estimated ANR in the crop was 7% in Year 1, 19% in Year 2, and 18% in Year 3 at the 44 Mg ha^?1 yard trimmings rate, compared with a mean ANR of 65% for the inorganic N treatment. Postharvest soil nitrate residual (0-to 120-cm depth) was similar for the 44 Mg ha^?1 treatment and inorganic N treatment. We observed variation in N availability with year and source of material. Yard trimmings also increased soil test K and organic matter.     

Agricultural zinc fluxes into soils and crops of central Iran at regional scale

Mass flux assessment can provide information that is essential for a sustainable management of elements in agricultural soils. In this article, we present an assessment of regional-scale averages of zinc (Zn) fluxes into agricultural soils and crops of central Iran for the period 1997–2011, using available databases such as regional agricultural statistics. The basic units of the balances were 15 townships of the provinces Qom, Isfahan and Fars. Averaged over the entire study region, the net Zn input into arable soil resulting from all fertilizer inputs – Zn removal with harvested crops was 1515 g ha^?1 yr^?1 across the entire region, with a range of 438–3009 g ha^?1 yr^?1 among townships. Estimated average Zn inputs with manure, mineral fertilizers, sewage sludge and compost were 1254, 531, 19 and 7 g ha^?1 yr^?1, respectively. The input-to-output ratio of these fluxes ranged from 1.8 to 12.9 among townships and averaged 6.1 for the entire study area. Considering that outputs other than with crop harvests are minor, Zn stocks are rapidly building up in the soils of the study region. Uncertainties in the manure and crop removal data were the main sources of estimation uncertainty in this study.     

Effects of nitrogen deposition on the acidification of terrestrial and aquatic ecosystems

The concentration of ammonium and nitrate in precipitation has increased during this century. The deposition of N compounds (wet + dry) is reaching 30 to 40 kg ha^?1yr^?1 in many areas in Central Europe and above 20 kg in the southern parts of Scandinavia. In extreme situations throughfall data indicate depositions above 60 kg ha^?1yr^?1 in Central Europe and above 40 kg ha^?1yr^?1 in south Sweden. Very high depositions are observed on slopes at forest edges and adjacent to areas with animal farms and manure spreading. In areas with low N deposition almost all deposited N (>95%) will be absorbed in the tree canopies or in the soil. In areas with high deposition an increased outflow is observed which in some cases reach 10 to 15 kg ha-lyr-1. The increased output is an indication of N saturation of the ecosystem and it leads to acidification effects in soils, soilwater, groundwater and surface waters.     

Soil and erosion features of the central plateau region of Tigrai,Ethiopia

The results of reconnaissance soil surveys covering 6,000 km² are used to describe the Central Plateau region, which lies at elevations of 2,000 to 2,800 m in northern Ethiopia. Landform and soil sequences on calcareous shales, dolerites and sandstones are described, in which the principal soil units are Lithosols, Luvisols, Cambisols, Arenosols and Vertisols. Detailed morphological and analytical data are presented for a profile representative of arable soils in each sequence.Small-scale subsistence cultivation of cereals is the dominant land use; all land which is physically cultivable is at present cultivated. Settlement patterns are closely related to soil type, nucleated settlement occurring on fine textured soils but dispersed settlement on coarser textured and more freely draining soils.Erosion and soil moisture features of the three landforms described were investigated and compared. Empirical methods and suspended sediment measurements indicate high rates of regional soil loss (17–33 t ha^?1 yr^?1), accounted for by seasonally high rates of rainfall erosivity, steep terrain and poor land use. The recent development of gully erosion is seen to be linked to the disintegration of waterfall tufas. Application of the universal soil loss equation to arable lands indicates potential annual soil losses in the range of 400 t ha^?1 on Vertisols to 200 t ha^?1 on Cambisols: differences in rates are ascribed principally to differences in crop planting dates, which affect the degree of vegetative protection during periods of high rainfall erosivity.Soil moisture is shown to be in the available range for less than three months in the year. The time at which moisture in the profile enters the available range differed between the three soils monitored and was found to be closely related to the crop planting date, thus indirectly affecting the erosion hazard.     

Long-Term Fertilization Effects on Rice Productivity and Nutrient Efficiency in Korean Paddy

ABSTRACT

Long-term fertilization tests evaluated rice (Oryza sativa) productivity in relation to application of nitrogen (N)-phosphorus (P)-potassium (K) (120-34.9-66.7 kg ha^{? 1}, respectively) during 1967–1972 and N-P-K (150-43.7-83.3 kg ha^{? 1}, respectively) during 1973–2000. The comparison treatments (NP, PK, and NK) and the control (not fertilized) were selected for calculating nutrient efficiency. Rice grain yield increased at a 17.78 kg ha^{? 1} yr^{? 1} in the control, mainly due to development of improved cultivars. Phosphorus management was found to be important for indigenous fertility and rice productivity in this paddy soil. Yield increased significantly with P fertilization. Without N fertilization (PK), rice productivity increased 56.85 kg ha^{? 1} yr^{? 1} from 62% of NPK at the initial stage to 74% after passing 34 years, which might be affected by increasing biological N fixation with P accumulation in soil. In NK treatment, rice yield increased at a relatively low rate (37.82 kg hr^{? 1} yr^{? 1}) from the same rice productivity with that of NPK in 1967 to 91% after 34 years. In comparison, yield increased at a high rate (62.82 kg hr^{? 1} yr^{? 1}) without K fertilization (NP) from ca. 90% of NPK and might exceed the yield of NPK after 64 years of long-term fertilization. Therefore, K fertilization level might be readjusted after long-term fertilizing in paddy soil.     

Assessing soil erosion and control factors by the radiometric technique in the Boussouab catchment,Eastern Rif,Morocco

In the Eastern Rif of N Morocco, soil conservation is seriously threatened by water erosion. Large areas of soil have reached an irreversible state of degradation. In this study, the ¹³⁷Cs technique was used to quantify erosion rates and identify the main factors involved in the erosion process based on a representative catchment of the Eastern Rif. To estimate erosion rates in terms of the main factors affecting soil losses, samples were collected taking into account the lithology, slope and land use along six selected transects within the Boussouab catchment. The transects were representative of the main land uses and physiographic characteristics of that Rif sector. The reference inventory for the area was established at a stable, well preserved, matorral site (value of 4250 Bq m^− 2). All the sampling sites were eroded and ¹³⁷Cs inventories varied widely (between 245 and 3670 Bq m^− 2). The effective soil losses were also highly variable (between 5.1 and 48.8 t ha^− 1 yr^− 1). Soil losses varied with land use. The lowest average values were on matorral and fallow land (10.5 and 15.2 t ha^− 1 yr^− 1, respectively) but much higher with alfa vegetation or cereal crops (31.6 and 27.3, respectively). The highest erosion rate was on a badland transect at the more eroded part of the catchment, with rates exceeding 40 t ha^− 1 yr^− 1 and reaching a maximum of 48.8 t ha^− 1 yr^− 1.The average soil losses increased by more than 100% when the slope increased from 10° (17.7 t ha^− 1 yr^− 1) to 25° (40. 8 t ha^− 1 yr^− 1). Similar results were obtained when comparing erosion rates in soils that were covered by matorral with respect to those under cultivation. Lithology was also a key factor affecting soil loss. Soils on marls were more erodible and the average erosion rates reached 29.36 t ha^− 1 yr^− 1, which was twice as high as soils on the glacis and old fluvial terraces (average rates of 14.98 t ha^− 1 yr^− 1). The radiometric approach was very useful to quantify erosion rates and to examine the pattern of soil movement. The analysis of main erosion factors can help to promote rational soil use and establish conservation strategies in the study area.