Non-fertilized Soil Research Articles

Nitrous oxide flux from soil amino acid mineralization

Nitrous oxide (N 2O) is a greenhouse gas produced during microbial transformation of soil N that has been implicated in global climate warming. Nitrous oxide efflux from N fertilized soils has been modeled using NO 3 − content with a limited success, but predicting N 2O production in non-fertilized soils has proven to be much more complex. The present study investigates the contribution of soil amino acid (AA) mineralization to N 2O flux from semi-arid soils. In laboratory incubations (−34 kPa moisture potential), soil mineralization of eleven AAs (100 μg AA–N g −1 soil) promoted a wide range in the production of N 2O (156.0±79.3 ng N 2O-N g −1 soil) during 12 d incubations. Comparison of the δ 13C content (‰) of the individual AAs and the δ 13C signature of the respired AA–CO 2-C determined that, with the exception of TYR, all of the AAs were completely mineralized during incubations, allowing for the calculation of a N 2O-N conversion rate from each AA. Next, soils from three different semi-arid vegetation ecosystems with a wide range in total N content were incubated and monitored for CO 2 and N 2O efflux. A model utilizing CO 2 respired from the three soils as a measure of organic matter C mineralization, a preincubation soil AA composition of each soil, and the N 2O-N conversion rate from the AA incubations effectively predicted the range of N 2O production by all three soils. Nitrous oxide flux did not correspond to factors shown to influence anaerobic denitrification, including soil NO 3 − contents, soil moisture, oxygen consumption, and CO 2 respiration, suggesting that nitrification and aerobic nitrifier denitrification could be contributing to N 2O production in these soils. Results indicate that quantification of AA mineralization may be useful for predicting N 2O production in soils.

Influence of Land-Use Management on Isotopically Exchangeable Phosphate in Soils from Burkina Faso

Little information exists on the effect of land use management on isotopically exchangeable phosphate (P) in agricultural soils of Burkina Faso. The 0–10 cm layer of 30 soils was sampled in February 1994 in 3 regions of Burkina Faso (in the east near Kouaré, in the south center near Thiougou and in the center in Saria). Four samples were taken under natural vegetation, 6 samples were taken in agricultural soils which had been left as fallow under natural re-growth, 7 samples were taken from soils cultivated without any P inputs and 13 samples were obtained from soils that had received P inputs in inorganic and/or organic forms. The phosphorus status of these soils was estimated by their total P (Pt), the Bray-1 extraction and by the isotopic exchange kinetic method (E1min the quantity of P isotopically exchangeable within 1 minute; E1min–1day the quantity of P isotopically exchangeable between 1 minute and 1 day; E1day–3m the quantity of P isotopically exchangeable between 1 day and three months; E>3m the quantity of P which cannot be isotopically exchanged within 3 months). The amounts of total P, Bray-1 P, and P isotopically exchangeable within three months were found to be very low in the non-cultivated soils (under natural vegetation or under fallow) (median values were for: Pt 145.1; Bray-1 P 1.7; E1min 0.16; E1min–1day 0.66; E1day–3m 1.34; E>3m 143.5 mg P kg−1 soil). Cropping these soils without any P input resulted in Kouaré in a slight decrease in isotopically exchangeable P compared to the non-cultivated soils, while no effect was observed in Thiougou. As the estimated P balances suggested that the amount of P removed annually from the non-fertilized systems was close or even larger than the amount of P isotopically exchangeable within the time span of growth of an annual crops (3 months) or than the Bray-1 P content of the soil, it appeared that crops derived a significant amount of their P from other sources. The mineralization of P associated to the soil organic matter, the release year after year of very slowly exchangeable P from the E>3m pool and the uptake of P from deeper layers could explain a significant fraction of the P uptake by crops in these non-fertilized systems. The amount of total P, Bray-1 P and of P isotopically exchangeable within 3 months increased when P was added to the soil as water-soluble P, phosphate rock or farmyard manure. There results show that natural fallow cannot be used as a practice to increase the P availability of soils to a level that would not be limiting for crop production and confirmed that to do so it is necessary to apply P fertilizers. Finally these results confirm that the Bray-1 P values are well correlated to the E1min values in the fertilized soils but that Bray-1 do not give a valuable information on soil P availability in non-fertilized soils.

Metal concentrations in three Montana soils following 20 years of fertilization and cropping

The presence of metals in some agricultural fertilizers has raised the concern that fertilized soils may be accumulating potentially toxic metals. A number of studies have been undertaken to determine the extent and significance of this potential problem, yet results have been mixed and the studies were not conducted in the Northern Great Plains. Therefore, a study was undertaken to determine if fertilization has increased metal concentrations in selected Northern Great Plain soils. Two irrigated sites and one non-irrigated site were selected; each had at least 20 years of fertilization and cropping history. Paired (fertilized and non-fertilized) soils from three depths (0–15 cm, 15–30 cm, and 30–45 cm) were sampled in replicate (n=10) and analyzed for a range of plant available and total metals, pH, organic matter, and phosphorus. In general, fertilized soils were found to have significantly lower levels of available and total metals than those of non-fertilized soils, indicating that long-term fertilization has not increased metal concentrations in the soils studied.

Effects of Chitosan Application on Chitinase Activity in Shoots of Rice and Soybean.

The effects of chitosan application on chitinase activity of rice and soybeans were investigated after incorporating it into soil before transplanting or seeding. In non-fertilized soil, the chitinase activity of rice increased from a chitosan application 2 weeks after transplanting, and it was continuously higher than control on 60, 90 and 120 days after the application. In fertilized soil, however, its effect was not clear. The effects of chitosan application on the chitinase activity of soybean were occasionally observed only in non-fertilized soil, and these effects of chitosan were found being different by crop.

Effect of increased cobalt treatments on sewage sludge amended soil: Nitrogen species in soil and tranference to tomato plants

The effects of increased cobalt additions (0, 50, 100 and 200 v mg v kg m 1 soil) in sewage sludge-amended soil on organic matter, N Kjeldahl, ammonium and nitrate were studied in this experiment. Three different rates of sewage sludge were applied (0, 30 and 60 v tn v ha m 1 ) to soil as main plots, using tomato (Lycopersicum esculentum Mill var. Ramy) such testing cultivation. Plant biomass and nitrogen content in tomato leaf were also monitored. The organic matter in the soil was clearly affected by the fertilization. N Kjeldahl, ammonium and nitrate were favoured by organic treatments. Co seemed to reduce the transformation of ammonium to nitrate on amended soils, with accumulation of ammonium forms, especially at the higher application rates of sewage sludge. This incidence of Co on nitrogen species in soil decreased with the time of experiment, probably due to the reduction of availability of the pollutant. Aerial biomass production and nitrogen content in leaf were increased for the organic fertilization compared to the control. Only very high levels of Co in soil reduced significantly the aerial biomass production of tomato plants in amended soils. Co seemed to induce a decrease of the nitrogen in leaf in the amended soils, but not for the non-fertilized soils.

Short-term effects of nitrogen and phosphorus fertilizers on nitrogen mineralization and trophic structure of the soil ecosystem in forest clearcuts in the southern interior of British Columbia

Ammonium sulphate and an ammonium sulphate-ammonium phosphate mixture were applied at 200 kg N ha-1 and 200 kg P ha-1 at three clearcut sites within the Interior Cedar-Hemlock biogeoclimatic zone in southern British Columbia. N mineralised under aerobic and anaerobic conditions, nitrification, biomasses of fungi and bacteria,the abundance of protozoa, and the trophic structure of nematode communities were studied at 4, 12, 16, and 28 mo after fertilisation. Nitrogen mineralised under aerobic conditions was greater in fertilised soil than in non-fertilised soil at 4 and 16 mo after fertiliser applications. Nitrification also increased after fertilisation. Fertilisation did not affect bacterial or fungal biomasses, but did increase the ratio of bacterial biomass/fungal biomass, the abundance of bacterivorous nematodes, and the ratio of bacterivorous nematodes/fungivorous nematodes. Thus, the fertiliser-induced increase in N mineralization appears to have been the result of increased bacterial decomposition and flow of carbon and nitrogen through bacteria-bacterivore channels of the soil food web. Key words: N mineralization, fertilisation, microbial biomass, microfauna, nematode ecology

Influence of soil properties on the turnover of nitric oxide and nitrous oxide by nitrification and denitrification at constant temperature and moisture

Soils are a major source of atmospheric NO and N2O. Since the soil properties that regulate the production and consumption of NO and N2O are still largely unknown, we studied N trace gas turnover by nitrification and denitrification in 20 soils as a function of various soil variables. Since fertilizer treatment, temperature and moisture are already known to affect N trace gas turnover, we avoided the masking effect of these soil variables by conducting the experiments in non-fertilized soils at constant temperature and moisture. In all soils nitrification was the dominant process of NO production, and in 50% of the soils nitrification was also the dominant process of N2O production. Factor analysis extracted three factors which together explained 71% of the variance and identified three different soil groups. Group I contained acidic soils, which showed only low rates of microbial respiration and low contents of total and inorganic nitrogen. Group II mainly contained acidic forest soils, which showed relatively high respiration rates and high contents of total N and NH4+. Group III mainly contained neutral agricultural soils with high potential rates of nitrification. The soils of group I produced the lowest amounts of NO and N2O. The results of linear multiple regression conducted separately for each soil group explained between 44–100% of the variance. The soil variables that regulated consumption of NO, total production of NO and N2O, and production of NO and N2O by either nitrification or denitrification differed among the different soil groups. The soil pH, the contents of NH4+, NO2– and NO3–, the texture, and the rates of microbial respiration and nitrification were among the important variables.

Effects of band placement and nitrogen rate on dry matter accumulation, yield and nitrogen uptake of cabbage, carrot and onion

Adequate nitrogen (N) nutrition is essential for producing high vegetable yields of good quality. Fertilizer N not taken up by the plants is, however, economically wasteful and can be lost to the environment. Therefore the efficient use of N fertilizer, involving accurate estimation of crop N demand, choice of application method and timing of N fertilization, is an important research area. The effects of band placement and rate of N fertilization on inorganic N in the soil and the dry matter accumulation, yield and N uptake of cabbage, carrot and onion were studied in a three-year field experiment between 1993 and 1995. The plants were sampled during the growing season to determine the dry matter accumulation and plant N concentration. The inorganic N in the soil was determined during the growing period and after harvest. The N uptake was 3.8 kg, 1.6 kg and 2.5 kg per ton of edible yield of cabbage, carrot and onion, respectively. At the highest yield levels the N uptake including crop residues was 300 kg ha-1, 150 kg ha-1 and 120 kg ha-1 in cabbage, carrot and onion, respectively. In cabbage, almost 50% of N was in crop residues, whereas in carrot and onion only about 30% of N was in crop residues. Nitrogen uptake from non-fertilized soil varied from 29 to 160 kg ha-1, depending on the growing season and the crop. Cabbage and carrot utilised soil N efficiently, usually taking up more than 100 kg ha-1 from non-fertilized soil. Onion, on the contrary, utilised soil N relatively poorly, usually less than 50 kg ha-1 from non-fertilized soil. The rate of N uptake was low with all crops in early summer. After one month, N uptake increased in cabbage and onion. This uptake continued until harvest, i.e. mid-August for onion and early September for cabbage. Nitrogen uptake by carrot started rapidly only two months after sowing and continued until harvest at the end of September. High N rates often resulted in high N concentrations and N uptakes, but growth was not necessarily increased. One month after fertilization, most of the N placed was still near the original fertilizer band and at the depth of 5-10 cm. At that time, broadcast N was at a depth of 0-5 cm. After harvest the soil mineral N content was generally low, i.e. below 25 kg ha-1 at the depth of 0-60 cm. Onion was an exception with poor growth in 1994, when soil mineral N after the highest N rate was 80 kg ha-1 at a depth of 0-60 cm after harvest. The placement distance in the cabbage experiment, 7.5 cm in the side and 7 cm below cabbage transplants, resulted in lower plant growth and N uptake than broadcasting of N at the beginning of the growing periods 1993 and 1994. Towards harvest differences between application methods decreased, although in 1993, placement of N still led to 6% lower cabbage yields than broadcasting of N. In 1993, high N rates increased cabbage dry weight and N uptake towards harvest, and this effect was more pronounced when N was broadcast. In 1994, soil N mineralisation was high, and only non-fertilized cabbages took up less N than fertilized plants. Carrot was remarkably insensitive to N fertilization. Carrot yields were similar with and without N fertilizers. Band placement and N rate did not affect carrot growth and N uptake. In 1993, band placement and high rates of N increased onion growth and bulb yield more than broadcasting. In 1994, onion growth was poor and treatments did not affect plant N concentrations or growth. Apparent recovery of fertilizer N was increased in 1993 by low N rates or band placement. This result that band placement of N does not much affect vegetable growth is in agreement with most previous studies. With onion, probably due to the sparse root system, positive effects of N placement are most likely to be found.;

Long‐Term Effects of Fertilization and Rotation on Denitrification and Soil Carbon

AbstractVarious long‐term crop management strategies are known to have differing effects on soil organic C. This laboratory study explored the effect of long‐term (35 yr) fertilization and crop rotation on soil organic C and denitrification capacity at different depths of a Brookston clay loam soil (fine‐loamy, mixed, mesic Typic Argiaquoll). We related denitrification capacity to soil biochemical (CO2 production, organic C, microbial biomass C, soluble organic C) and soil structural properties. Denitrification capacity was determined as the increase in N2O that occurred when NO‐3‐amended soils were incubated anaerobically in the presence of acetylene. Treatments included fertilized and nonfertilized plots of continuous corn (Zea mays L.), continuous bluegrass (Poa pratensis L.), and rotation corn (corn‐oat [Avena sativa L.]‐alfalfa [Medicago sativa L.]‐alfalfa). Soils from an adjacent mixed deciduous woodlot were also sampled. Soils from the woodlot had higher denitrification capacities than the continuous or rotation corn treatments. Among the agricultural treatments, the soil under bluegrass had the greatest denitrification capacity followed by the soil under corn rotation, with the continuous corn having the lowest capacity. Long‐term fertilization resulted in 35% higher denitrification capacity and 65% higher CO2 production than nonfertilized soils. Denitrification capacity across all depths in the agricultural soils was correlated with CO2 production (r2 = 0.76), microbial biomass C (r2 = 0.60), and organic C (r2 = 0.54); however, the relationship between denitrification capacity and soil structure was not as strong (r2 = 0.28).

THE EFFICIENCY OF DIFFERENT AMOUNT OF CATTLE DUNG ON SOIL MICROORGANISMS AIMING AT FARM ENVIRONMENT PROTECTION

An exact vegetation experiment regarding investigation of efficiency of different liquid amount enriched with technological liquid waste on prevalent microbiological associations in soil type loessive semigley was set out at a farm in Eastern Croatia during 1997.The experiment variants were as follows: 1. liquid manure with disinfectants in the following doses: 1 l/m2 (30 kg N/ha), 1.5 l/m2 (45 kg N/ha), 2 l/m2 (60 kg N/ha), 3 l/m2 (90 kg N/ha); 6.5 l/m2 (195 kgN/ha); 2. NPK (180:110:160 kg/ha); 3. control - nonfertilized soil. Amounts of liquid farmyard manure enriched with disinfectants applied into tilth soil layer are very significant for condition and activity of physiological groups of microorganisms .Thus, smaller doses (1-3 l/m2) cause lower and relatively short term decrease of aminoheterotrophies, aminoautotrophies and asymbiotic nitrogen fixers (A. chroococcum). Higher doses (6.5 l/m2) cause stronger and long term decrease of the same physiological groups of microorganisms.

Cotton root growth as affected by P fertilizer placement

Growth chamber studies were conducted to evaluate root growth and P uptake by cotton (Gossypium hirsutum L.) as affected by the proportion of the soil volume that is treated with fertilizer P. Cotton seedlings were grown in a Dewey silty clay loam (Typic Paleudult) and a Marvyn loamy sand (Typic Paleudult). The Dewey soil had a low-P status and the Marvyn soil had a high-P status (7 and 44 mg kg−1 Mehlich I extractable P, respectively). Phosphorus was added at a constant or base rate which was added to decreasing proportions of the soil volume (i.e. 1.0, 0.5, 0.25 and 0.125). The addition of the same amount of P to decreasing proportions of the soil volume resulted in a stimulation of root growth in the P-fertilized soil volume relative to the nonfertilized soil. The degree of stimulation was similar for the two soils which differed in P status. Phosphorus uptake reached a maximum when 0.25 and 0.50 of the soil volume was treated with P on the Marvyn and Dewey soils, respectively.

A Preliminary Investigation of Sorption and Mobility of Phosphate in a Danish Spodosol

Abstract A preliminary comparative phosphate sorption and mobility study of two almost identical Danish spodosols, a fertilized soil having received ≍ 1030 kg P/ha over 45 years and a non-fertilized soil, showed no indication of increased phosphate leaching out of the profile from the fertilized soil compared to the non-fertilized soil. The Langmuir sorption capacity (Pmax) determined on air-dried samples could be accounted for by the aluminium and iron oxides, but Pmax corresponds to phosphate concentrations too high for the aquatic environment. However, estimates indicate that phosphate loadings up to ≍ 0.1 Pmax in Bh and Bhs horizons and up to ≍ 0.3 Pmax in Bs and C horizons (so-called critical phosphate loads) can be tolerated.

Root growth and the relative importance of root and shoot competition in interactions between rice (Oryza sativa) and Echinochloa crus‐galli

Competition between rice (Oryza sativa) and Echinochloa crus-galli (L.) Beauv. (barnyard-grass or cockspur) was studied experimentally in the field in Sri Lanka. By growing rice in bags sunk in the paddy soil such.that the roots of the plants were either separated from or free to mingle with those of neighbouring weeds, or by growing rice in the same bags but in the absence of weeds, it was possible to calculate the relative importance of interference below ground (root competition) and above ground (shoot competition). Three rice varieties with different above-ground morphology were inhibited to different extents by E. crus-galli but in each case root competition was more important than shoot competition. In the variety that was most sensitive to root competition, Bg 400–1, inhibition of total growth due to root competition increased with increasing weed density. When grown in monocultures in pots in the field, the two species exhibited similar growth rates whether or not the soil was fertilized, but in 1:1 mixtures growth of E. crus-galli was greater, particularly if fertilizer was added, as this promoted the growth of the weed, while having no effect on the rice. In mixture, relative yield totals were close to 1.0, with the relative yield of E. crus-galli being consistently greater than 0.5, particularly with added nutrients, while the relative yield of rice was always less than 0.5. The relative crowding coefficient for rice with respect to E. crus-galli (Keb), when based on total plant dry weight, was lower in fertilized than in non-fertilized soil, falling in the former case from 0.4 to 0.2 during the experiments Krootrb, based on root dry weight, decreased with increasing soil depth and was lower in fertilized than in non-fertilized soil, most notably after 62 days of growth, when root dry weight was at its maximum. It is concluded that inhibition of root growth of rice, leading to a reduced ability to obtain resources from the soil, was the major factor contributing to the decline in the growth of rice in the presence of E. crus-galli.

Autotrophic nitrification in a fertilized acid heath soil

The nature of nitrification in fertilized, acid heath soils was studied. Autotrophic ammoniumand nitrite-oxidizing bacteria were enumerated in non-fertilized and fertilized heath soils. Ammoniumoxidizing bacteria were not detected in the non-fertilized soils, whereas nitrite-oxidizing bacteria were only found in the organic layer. Enrichment of acid heath soils with NPK fertilizer increased the number of autotrophic ammonium- and nitrite-oxidizing bacteria in the organic (F + H) layer as well as in the upper part of the mineral (Ah) layer, although the pH of the soil hardly changed with fertilization. In soil suspensions of the upper mineral layer of fertilized heath soils, nitrification was shown to be autotrophic as nitrification was completely inhibited by the addition of nitrapyrin under both neutral and acid conditions. Stimulation of nitrification by addition of peptone appeared to be due to the increase in pH caused by ammonification of peptone. Under acid conditions, nitrification seemed to be coupled with net nitrogen mineralization. The possible influence of vegetation on nitrification is discussed.

Soil solarization: Effects on soil properties, crop fertilization and plant growth

Summer solarization of six wet field soils of four different textures raised soil temperatures by 10–12°C at 15cm depth. Soil solarization increased concentrations of NO − 3N and NH + 4N up to six times those in nontreated soils. Concentrations of P, Ca 2+, Mg 2+ and electrical conductivity (EC) increased in some of the solarized soils. Solarization did not consistently affect available K +, Fe 3+, Mn 2+, Zn 2+, Cu 2+, Cl − concentrations, soil pH or total organic matter. Concentrations of mineral nutrients in wet soil covered by transparent polyethylene film, but insulated against solar heating, were the same as those in nontreated soil. Increases in NO − 3N plus NH + 4N were no longer detected in fallowed soils 9 months after solarization. No significant correlation between mineral-nutrient concentration in plant tissue and plant growth was found. Fresh and dry weights of radish, pepper and Chinese cabbage plants usually were greater when grown in solarized soils than in nontreated soils. Fertilization of solarized soils sometimes resulted in greater plant growth responses than observed in solarized but nonfertilized soils.