Antoine Karam

Mineralization of Nitrogen and Carbon in Soils Amended with Composted Manure

ABSTRACT A study was conducted under laboratory conditions to determine the quantity of N mineralized from four composted manures incorporated into 2.7 kg of St-Jude sand or Tilly silty loam at rates of 0.05%, 0.10% and 0.20% of total N. With one exception (a hog slurry-sawdust based compost), net cumulative mineralization of N (Nm) during successive incubation periods increased with incubation time and with the rate of addition. After four months of incubation, Nm values varied from 0 to 14% of total added N. A significant third order interaction on Nm values was obtained with compost type, application rate and soil type. Net immobilization of N was apparent at all incorporation rates of hog slurry compost in the two soils. To evaluate C mineralization, composts were applied at the highest N rate and CO2 production measured periodically. One to 8.2% of total added C from manure composts was mineralized after 28 days of incubation. For each compost type, C mineralization was higher with the sandy than wit...

Potential of Sphagnum peat for improving soil organic matter, water holding capacity, bulk density and potato yield in a sandy soil

Low soil organic matter content and limited soil water holding are the major natural constraint of dryland cropping on sandy soils in the Quebec boreal regions. We conducted a 3-yr (1994–1996) study in a boreal sandy soil, Ferro-Humic Podzol (Spodosols), to determine the potential of Sphagnum peat for improving soil organic matter (SOM), water holding capacity, bulk density (BD), plant leaf nutrient status, and potato and barley yields. The cropping was a rotation of 2-yr potato (Solanum tuberosum L. ‘Superior’) and 1-yr barley (Hordeum vulgare L. ‘Chapais’). The treatments consisted of Sphagnum peat at rates of 0, 29, 48, and 68 Mg ha−1 3-yr−1 on a dry weight basis, and granular N-P-K fertilizers (12-7.5-7) at rates of 1.4, 1.6, and 1.8 Mg ha−1 yr−1, respectively, arranged in a split-block design. The peat-amended soils were higher in water content (SWC), SOM and total porosity but lower in BD and N than neighboring non-peat soils (P < 0.05). Effects of peat and fertilizer treatments and their interaction were significant on potato leaf N, Ca, Mg, and P, tuber yield, dry weight, harvested N and tuber specific gravity (P < 0.05), depending on year. Potato tuber yield and N increased simultaneously up to 30% (compared to the control), and were significantly correlated with SWC, SOM, BD, and NO3-N (−0.52 ≤r ≤ 0.80). In the 3rd year, the linear effect of peat treatments was significant on barley grain yield. In 1995 there was a decline of 4.5−7.3% of SOM of the previous year level. It is suggested that Sphagnum peat at a rate of 48 Mg ha−1 had the potential for improving sandy soil productivity. A longer-term investigation of soil water, N, SOM pool and crop yield changes is necessary to better understand the physical, chemical and biological processes of peat in cropping systems and to maximize the benefits of peat applications.

Efficiency of soil and fertilizer nitrogen of a sod-potato system in the humid, acid and cool environment

It was hypothesized that soil N variability, and fertilization and cropping management affect potato (Solanum tuberosum L.) growth and fertilizer N efficiency. Following a 20-year sod breakup on a loamy soil in eastern Quebec, Canada (46°37′ N, 71°47′ W), we conducted a 3-year (1993–1995) study to investigate the effects of soil pool N and fertilizer N management on non-irrigated potato (cv. Superior) tuber yield, fertilizer N recovery (NRE), and residual N distribution in soils under humid, cool and acid pedoclimatic conditions. The fertilizer N treatments consisted of a control, side-dress at rates of 70, 105 and 140 kg ha−1, and split applications (at seeding and bloom) at rates of 70+70, 105+70 and 140+70 kg ha−1, respectively. Soil acidity was corrected with limestone following the plow down of the sod. Years of cropping, main effect of N treatment, and year and fertilizer N interaction were significant on total and marketable tuber yields and N uptake, which were significantly related to soil N, and root growth. Apparent NRE ranged between 29 and 70%, depending on years and N rates. Total tuber yield, N uptake, soil N use and NRE were significantly higher in the first (sod–potato) year, but decreased by 41.8, 22.7, 21.4 and 14.7%, respectively, in the third (sod–potato–potato–potato) year. Initial soil N pool was declined by 75% following the 3-year cropping. In 2–3 years, the side-dress N (140 kg ha−1) increased significantly tuber yields (11.4–19.8%) compared to the split N (70+70 kg ha−1). Higher split N had no effect on tuber yield and N uptake but increased residual N at harvest. Unused fertilizer N was strongly linked (R2=0.98) to fertilizer N rates. Time factor and N treatment had significant effects (P<0.0001) on loss of N to below the root zone. Smaller scale rate and timing of split N need to be further determined. Increasing fertilizer N use efficiency could be expected with sod breakup and 75% of regional recommendation rate under humid, cool and acid pedoclimatic conditions.

Effect of NH4+:NO3- ratios on growth and nitrogen uptake by onions

The modelling of ion uptake by plants requires the measurement of kinetic and growth parameters under specific conditions. The objective of this study was to evaluate the effect of nine NHinf4sup+:NOinf3sup−ratios on onions (Allium cepa L.). Twenty-eight to 84 day-old onion plants were treated with NHinf4sup+:NOf3/sup− ratios ranging from 0 to 100% of each ionic species in one mM solutions in a growth chamber. Maximum N influx (Imax) was assessed using the N depletion method. Except at an early stage, ionic species did not influence significantly Imax, the Michaelis constant (Km) and the minimum concentration for net uptake (Cmin). Imax for ammonium decreased from 101 to 59 pmole cm-2 s-1 while Imax for nitrate increased from 26 to 54 pmole cm-2 s-1 as the plant matured. On average, Km and Cmin values were 14.29 μM, and 5.06 μM for ammonium, and 11.90 μM and 4.54 μM for nitrate, respectively. In general, the effect of NH4+:NO3- ratios on root weight, shoot weight and total weight depended on plant age. At an early stage, maximum plant growth and N uptake were obtained with ammonium as the sole source of N. At later stages, maximum plant growth and N uptake were obtained as the proportion of nitrate increased in the nutrient solution. The was no apparent nutrient deficiency whatever NH4+:NO3- ratio was applied, although ammonium reduced the uptake of cations and increased the uptake of phosphorus.

Arbuscular Mycorrhizae and Alleviation of Soil Stresses on Plant Growth

Within the last decade, inventories of the soil’s productive capacity indicate severe degradation and loss of arable lands as a result of soil erosion, cultivation, salinization, over-grazing, land clearing, desertification, soil pollution, and atmospheric pollution. Large areas of land have been, and continue to be, contaminated by trace metals, and petroleum hydrocarbons. Many technologies using physical and chemical treatment methods have been developed to remediate contaminated soils. Recently, phytoremediation has been thought to provide an environmentally friendly alternative for the treatment of polluted soils. In phytoremediation of metal-contaminated soils, bioavailability and metal uptake are important factors. Among soil-plant factors controlling metal uptake, the rhizosphere flora is known to play a special role in the phyto-availability of trace elements. In this regard, arbuscular mycorrhizal fungi (AMF), which are among the most common components of soil rhizosphere flora, is of great interest to soil and environmental scientists, from a phyto-remediation and an environmental standpoint. AMF play important roles in the restoration of contaminated ecosystems and are increasingly used in many countries to improve plant nutrition and fertility of degraded land. As AMF are becoming commercially available, their use will also provide further avenues for reducing pollution from agriculture. This chapter reviews the role, the importance, and the application of AMF in ecologically remediating contaminated soils (mycorrhizoremediation). Emphasis is given to the effects of AMF on growth and yield, and on the uptake of trace metals by plants (rhizo-availability) from agricultural and metal-contaminated soils. The chapter also addresses the AMF’s potential for improving or sustaining soil fertility.

Effect of a commercial peat moss-shrimp wastes compost on pucinellia growth in red mud

Abstract Revegetation of red mud can be difficult without chemical or organic ameliorant for red mud. A greenhouse experiment was conducted to examine the short-term effect of a commercial peat moss-shrimp wastes compost on the growth of pucinellia (Pucinellia distorts L.) in a bauxite residue (red mud) from the Alcans Vaudreuil alumina refinery at Jonquiere (Quebec), Canada. Characterization of the red mud revealed that the residue was strongly alkaline (pHse=11.4) and contained soluble salts (ECse=10.3 dS m−1), soluble Na (2743 mg L−1), soluble Al (275 mg L−1) and low levels of plant-available nutrients. Red mud components included approximately 40.4% Fe, 18.3% Al, 13.4Percnt; Si, 7.5% Ti, 6.7% Na and 3.5% Ca expressed in oxide. Hematite (∝Fe2O3) was the main mineral in the red mud. The results of the revegetation study have shown that compost amendment treatments affected pH values, salinity, organic carbon and DTPA-exlractable Al contents compared to the control. The highest rate (45%) of compost red...

Impact of organic amendments on aerial biomass production, and phytoavailability and fractionation of copper in a slightly alkaline copper mine tailing

In the process of phytoremediation of mine tailing land, the bioavailability of heavy metals is an important factor. Greenhouse experiment was conducted to assess the availability and uptake of copper (Cu) by maize (Zea mays L.) grown on a slightly alkaline Cu-mine tailing amended with commercial compost and chelators. A second objective was to evaluate the distribution of Cu in cultivated Cu-mine tailings. The experimental design consisted of 12 treatments resulting from the combination of four rates (0, 5, 10 and 20%, by humid weight) of peat moss-shrimp wastes compost and three rates (0, 1.2 and 2.4 dm3) of organic complexing agents applied as a 0.0025 M EDTA + 0.001 M citric acid solution before plant harvest. The results showed that compost and chelators had a positive effect on top biomass production of maize. Compared with the control, the application of compost decreased CuCAR and increased CuORG whereas the addition of chelating solution increased CuSOL and CuEXC and decreased CuCAR and CuORG. The Cu lability in cultivated tailing and its availability to the maize plant are highly dependent on the metal speciation in tailing. In another series of experiments, sorption of Cu by cultivated mine tailings were examined. The amounts of Cu sorbed and K d values were highest in tailing amended with highest compost rate, and were positively correlated with tailing organic matter (OM) content and Cu bound to CuORG. The results indicate that peat moss and shrimp waste containing compost could be used as a phytostabilizer by supplying OM and nutrients and as a sorbent by mitigating Cu uptake by maize. This compost is able to improve the phytoremediation of Cu-mine tailings.

Metal Availability following Paper Mill and Alkaline Residuals Application to Field Crops.

Land application of residuals from the forest industry can help to restore soil fertility, but few studies have assessed the effects of metal accumulation in plants. An experimental study was initiated in 2000 on a loamy soil at Yamachiche, QC, Canada, to evaluate the effects of repeated annual applications of combined paper mill biosolids, when applied alone or with several liming by-products. This study assessed the accumulation of Cu, Zn, Mo, and Cd in plants and soil after 6 (soybean [ (L.) Merr.]) and 9 [corn ( L.)] crop yr. Wet paper mill biosolids at 0, 30, 60, or 90 Mg ha were surface applied after seeding. Calcitic lime, lime mud, and wood ash were applied wet each at 3 Mg ha with 30 Mg wet paper mill biosolids ha. Repeated applications of paper mill biosolids increased plant and soil metal concentrations after 6 and 9 yr in the order of Cd > Mo (soybean) > Zn > Cu. Liming increased soil pH and Mo availability and decreased Zn and Cd availability. Metals in crop stover responded more positively to applications than those in grains, but the concentrations in plant tissues were generally well below critical values. The Cu/Mo ratio of soybean plants at pH > 6.8 fell below 2:1, however, and may pose a risk for inducing Cu metabolism disorder in ruminants. Results of this study indicate that paper mill biosolids and alkaline residuals, when applied with respect to regulations and soil pH, have a limited effect on metal accumulation in plants and soil.

Repeated Annual Paper Mill and Alkaline Residuals Application Affects Soil Metal Fractions

The application of industrial residuals in agriculture may raise concerns about soil and crop metal accumulation. A complete study using a fractionation scheme would reveal build-up in metal pools occurring after material addition and predict the transformation of metals in soil between the different forms and potential metal release into the environment. An experimental study was conducted from 2000 to 2008 on a loamy soil at Yamachiche, Quebec, Canada, to evaluate the effects of repeated annual addition of combined paper mill biosolids when applied alone or with several liming by-products on soil Cu, Zn, and Cd fractions. Wet paper mill biosolids at 0, 30, 60, or 90 Mg ha and calcitic lime, lime mud, or wood ash, each at 3 Mg ha with 30 Mg paper mill biosolids ha, were surface applied after seeding. The soils were sampled after 6 (soybean [ (L.) Merr.]) and 9 [corn ( L.)] crop years and analyzed using the Tessier fractionation procedure. Results indicated that biosolids addition increased exchangeable Zn and Cd, carbonate-bound Cd, Fe-Mn oxide-bound Zn and Cd, organically bound Cu and Zn, and total Zn and Cd fractions but decreased Fe-Mn oxide-bound Cu in the uppermost 30-cm layer. With liming by-products, there was a shift from exchangeable to carbonate-bound forms. Even with very small metals addition, paper mill and liming materials increased the mobility of soil Zn and Cd after 9 yr of application, and this metal redistribution resulted into higher crop grain concentrations.