Ion distribution in leaves of varying age in salt‐tolerant lines of alfalfa under salt stress

Two lines of alfalfa (Medicago sativa L.), a salt‐tolerant AZ‐Germ Salt II and a salt‐sensitive Mesa Sirsa, were grown for three weeks in solution culture containing 0 or 100 mol/m³ sodium chloride (NaCl) in half‐strength Hoagland nutrient solution. Distribution of cations and chloride (Cl) in the leaves of varying ages was determined. The older leaves (age‐dependent) of both lines contained more sodium (Na) in the laminae and petioles than the younger leaves at the salt treatment, whereas the reverse was true for potassium (K) in the laminae. Age‐dependent Cl distribution was only found in the laminae of AZ‐Germ Salt II. Distribution of calcium (Ca) in the lamina and petioles was strongly age‐dependent in both lines, but such a pattern was not found for magnesium (Mg) concentrations. AZ‐Germ Salt II accumulated considerably higher concen‐ trations of Na and Cl in the laminae compared with Mesa Sirsa. The lower Na and Cl concentrations in the laminae of Mesa Sirsa were due to relatively higher accumulation of these ions in the stems. It is concluded that distribution of Na, Cl, and Ca in the leaf laminae is age dependent. Salt tolerance in alfalfa is related to inclusion of Na and Cl in the leaf laminae.     

Growth of tomato seedlings under different HCO‐ 3 concentration in the medium

An increase in the concentration of HCO^‐ ₃ ions in liquid media surrounding the root system significantly affected the biomass production of tomato seedlings in early stages of growth. This effect depended upon HCO^‐ ₃ concentration. The cultivation of seedlings during a period of 24 days (from 21–45 days after sowing) on a medium enriched to 5.68 mM HCO₃ (0.025% CO₂ after the computed dissociation) increased the production of dry matter (DW) plant"¹ to about 179% as compared with the respective control. Various tomato organs showed different values of DW increase, the greatest one being noted in leaf blades. This result was correlated with an increase in leaf blade area to about 176% in relation to the control. With an increase in the concentration to 22.72 mM HCO^‐ ₃ (0.1% CO₂ after the computed dissociation) a general tendency of changes was maintained, however, the absolute values of growth were diminished. In media of an enriched HCO₃ content the length of shoots, and roots, was not significantly modified. The values of other growth parameters computed for the respective three experimental series with HCO₃ concentration of 0.0, 5.68, and 22.72 mM, respectively, in the medium also showed correlations with the biomass production in tomato organs. The enrichment of liquid media with HCO₃ affected the processes of absorption, distribution, and accumulation of such elements as nitrogen, potassium, and calcium. No statistically significant differences in the content of phosphorus were obtained. The data presented here are the continuation of the study whose results were published in 1992 (J. Plant Nutr. 15: 293–312).     

Effect of salinity × calcium interaction on cation balance in melon plants grown under two regimes of orthophosphate

Melon (Cucumis melo L.) plants were grown hydroponically in a greenhouse to investigate the interaction of phosphorus (P) and calcium (Ca) under saline conditions on vegetative biomass and cation balance. Three levels of Ca (0.4, 2, and 8 mM) were combined factorially with two levels of phosphate (0.1 and 1 mM) under two regimes of NaCl salinity (10 and 80 mM). An increase of phosphate and salinity level decreased shoot and root growth. A strong antagonism between Ca and magnesium (Mg) was observed regardless of the salinity level. Calcium effect on growth depended on the salinity level. At low salinity, an increase of Ca reduced sodium (Na) concentration in all plant fractions. At high salinity, this effect was only significant in young and medium leaves. At low salinity and low Ca the reduction of growth could be due to Na toxicity and an unbalanced Ca/Mg ratio. In addition to that, at high salinity, the restoration of growth by increasing Ca concentration in the root medium could be due to an effect on water relation and by increasing potassium K/Na selectivity.     

Improvement of the nitrogen uptake induced by titanium (iv) leaf supply in nitrogen‐stressed pepper seedlings

The beneficial effect of titanium (Ti) on plant metabolism can result in more profitable use of fertilizer applied to a crop. A crop chamber experiment with paprika pepper (Capsicum annuum L., cv. Bunejo) seedlings under differential nitrogen (N) concentration levels in a nutrient solution (100% N, 75% N, 50% N, and 25% N) was performed. A third of the seedlings growing under each N support level remained Ti‐untreated and were used as the reference. Another third of the seedling received one and two 0.042 mM Ti(TV) ascorbate, pH 6.0, leaf spray treatments, respectively. The biomass production of the Ti‐untreated plants was only affected by the N supply of 50% or less. The Ti(IV) leaf spray treatments produced a biomass production greater than that of the corresponding reference plants, and both the 100% N+Ti and 75% N+Ti treatments had the highest biomass production. Seedlings receiving 50% N+Ti had a level of biomass production similar to that for the 100% N without Ti reference plants. In the same way, the 25% N+Ti treatment resulted in a plant fresh weight greater than that for the Ti‐untreated reference plants, although their biomass yields were not significantly lower than that for the corresponding 100% N and 75% N Ti‐untreated reference plants. Only the 50% N and 25% N Ti‐untreated plants had definite total‐N and nitrate‐nitrogen (NO₃‐N) unbalances as compared to the other N rate‐Ti treatments.     

Monitoring potassium in alfalfa using a hand‐held ion‐specific electrode

Abstract

A reliable method to rapidly assess the potassium (K) status of alfalfa (Medicago sativa L.) would enhance the ability of producers and crop consultants to make timely decisions regarding K fertilization. Recently introduced to the agricultural market are portable, hand‐held, ion‐specific electrodes, that allow direct measurement of K in plant sap. The objective of this study was to compare the potassium ion‐specific electrode (KSE) meter to flame photometry as a tool to estimate the K status of alfalfa. A total of 75 fields in the low deserts of California and Arizona were sampled in June and again in November‐December of 1995. Seventy‐five mid‐stems from each field were collected and chopped into 1 cm pieces. Sap was extracted from half the sample and analyzed for K concentration with the KSE meter. Sap readings were taken either immediately in the field (method 1) or after transport to the laboratory (method 2). The other half of the sample was oven dried at 60°C and analyzed for K concentration via flame photometry. Sap K concentration by method 1 was well correlated (r²=0.68) with flame photometry; field pressed, but laboratory analyzed samples (method 2) were not as well correlated. In conclusion, the KSE meter could be used as a quick and inexpensive tool to monitor the K concentration of alfalfa mid‐stems if samples are extracted and read immediately in the field.     

Inorganic nitrogen supply and symbiotic dinitro‐gen fixation in alfalfa

It may be desirable to minimize dinitrogen (N₂) fixation in alfalfa (Medicago saliva L.) when a source of inorganic nitrogen (N), such as manure, is readily available. Our objectives were to determine the N₂ fixation response of eight alfalfa germplasms to inorganic N and to characterize plant‐to‐plant variation for this trait. Seed was sown in vermiculite and irrigated with nutrient solution in growth chambers. Herbage was removed at 71 d and treatments of 1, 3, 5, or 10 mM N were applied as ¹⁵N‐depleted ammonium nitrate (NH₄NO₃). After 34 d of regrowth, herbage was removed and analyzed for dry mass, total N concentration, and N isotope ratio. Increased availability of inorganic N resulted in a linear increase in herbage weight, height, shoot number, and N concentration, and consistently decreased N₂ fixation for all germplasms. Estimated N₂ fixation was greater than zero at the highest rate of inorganic N, which we speculate was due, in part, to remobilized root and crown N, because nodules appeared to be nonfunctional. Across all treatments, N₂ fixation correlated best with herbage N concentration, but there was no relationship between these variables within a given N treatment concentration. Significant variation in reliance on N₂ fixation in the presence of inorganic N existed in all eight germplasms.     

K‐Fertilization under different Agroecological conditions studied with maize

In Hungary the AL‐method using ammonium lactate acetic acid as extradants has been widely used for serial analysis of soil potassium and phosphorous available to plants in the last 30 y. Because of the considerable increase of the price of fertilizers and decline of the economic situation, there is a pressing need for cost‐effective fertilizer use. Recently this highlighted the importance of nutrient recommendations based on soil analyses. Small plot long‐term field fertilization experiments are the best means to quantify the efFect or the efficiency of K‐fertilization. Long‐term data sets can reveal on which soil type which crop responds most favourably to the different fertilizer doses and nutrient ratios under different, long‐term balanced soil nutrient levels. Since the experimental data of the National Long‐Term Field Trials reflect the agro‐ecological conditions of nine experimental sites representing different soil types of Hungary, these experiments provide excellent opportunity to study this topic. The trials were set up in 1967 with 20 fertilization treatments including three increasing N‐and P‐levels each, two K‐levels and their different combinations. From the experimental data of great number only those of four sites will be shown. Winter wheat, maize, and pea have been grown as test plants. In the experiment selected for presentation, maize had statistically proved responses to K‐fertilization. The efficiency of K‐fertilizer on different soil types shows, however, significant differences, which can not be completely explained with the results of K‐analysis gained with the AL‐method.     

Gas exchange,water relations,and Ion concentrations of salt‐stressed tomato and melon plants

Abstract

Tomato and melon plants were grown in a greenhouse and irrigated with nutrient solution having an EC of 2 dS m^?1 (control treatment) and 4, 6, and 8 dS m^?1, produced by adding NaCl to the control nutrient solution. After 84 days, leaf water relations, gas exchange parameters, and ion concentrations, as well as plant growth, were measured. Melon plants showed a greater reduction in shoot weight and leaf area than tomato at the two highest salinity levels used (6 and 8 dS m^?1). Net photosynthesis (Pn) in melon plants tended to be lower than in tomato, for all saline treatments tested. Pn was reduced by 32% in melon plants grown in nutrient solution having an EC of 4 dS m^?1, relative to control plants, and no further decline occurred at higher EC levels. In tomato plants, the Pn decline occurred at EC of 6 dS m^?1, and no further reduction was detected at EC of 8 dS m^?1. The significant reductions in Pn corresponded to similar leaf Cl^? concentrations (around 409 mmol kg^?1 dry weight) in both plant species. Net Pn and stomatal conductance were linearly correlated in both tomato and melon plants, Pn being more sensitive to changes in stomatal conductance (g_s) in melon than in tomato leaves. The decline in the growth parameters caused by salinity in melon and tomato plants was influenced by other factors in addition to reduction in Pn rates. Melon leaves accumulated larger amounts of Cl^? than tomato, which caused a greater reduction in growth and a reduction in Pn at lower salinity levels than in tomato plants. These facts indicate that tomato is more salt‐tolerant than melon.     

Ion interactions in calcium‐efficient and calcium‐inefficient tomato lines 1

Two Ca‐efficient and 3 Ca‐inefficient tomato lines selected on the basis of dry matter production, Ca concentrations in tissues, and severity of Ca deficiency symptoms were grown in nutrient solutions containing 6 levels of total Ca ranging from 15 to 365 mg in 70 mg increments. All lines responded to increased Ca supply by increasing in dry weight and by accumulating Ca. The critical Ca concentrations in the shoots were 0.25% and 0.40% on a dry weight basis for the efficient and inefficient lines, respectively. Concentrations of Ca, K, Mg, P, and NO₃ ^‐ were lower in shoots and except for Mg were lower in roots of efficient plants than in the inefficient plants. For all lines as more Ca was available in the media and as Ca increased in the shoots and roots, the concentrations of the nutrients other than Ca declined. The declines in concentrations of K and Mg were not due to dilution by higher dry matter production in the efficient lines relative to the inefficient ones, although the total accumulation of Ca, P, and NO₃ ^‐ did not vary with Ca supplied. Antagonism among cations may account for differences in efficiency among lines of tomato.     

Partitioning of biomass in water‐ and nitrogen‐stressed cotton during pre‐bloom stage

The partitioning of biomass between aboveground parts and roots, and between vegetative and reproductive plant parts plays a major role in determining the ability of cotton (Gossypium hirsutum L.) to produce a crop in a given environment. We evaluated the single and combined effects of water and N supply on the partitioning of biomass in cotton plants exposed to two N supply levels, 0 and 12 mM of N, and two water regimes, well irrigated and water‐stressed at an early reproductive stage. The N treatments began when the third true leaf was visible, while water deficit treatments were imposed over the N treatments when the plants were transferred into controlled‐environment chambers at a leaf area near 0.05 m². Both water deficits and N deficits inhibited total biomass accumulation and its partitioning in cotton. Water deficit alone and N deficit alone inhibited the growth of leaves, petioles, and branches, but did not inhibit growth of the stem and enhanced the accumulation of biomass in squares. When water deficit was superimposed on N deficit, leaf growth was inhibited, although to a lesser extent than when it was the sole stress factor, and the accumulation of biomass in squares was also inhibited. Yet, the dry weight of squares in plants exposed to water and N deficits was greater than that of non‐stressed plants. Water and N deficits, either alone or in combination, did not inhibit the growth of the tap root. Growth of lateral roots was not inhibited either by water deficit alone or in combination with N deficit, but was enhanced when plants were exposed to N deficit alone. Exposure to water deficit alone or in combination with N deficit decreased the shoot:root ratio through the inhibition of shoot growth. Exposure to N deficit alone decreased the shoot:root ratio through the combination of shoot growth inhibition and root growth enhancement.     

Changes in herbage chemical composition due to proportion of species in alfalfa‐orchardgrass mixtures

Abstract

Legumes and grasses are widely grown in mixtures throughout the United States and Canada. This study was conducted to determine the changes in chemical composition of herbage that occur as proportion of legume and grass change in the mixture. Composition of mixtures of alfalfa (Medicago sativa L.) and orchardgrass (Dactylis glomerata L.) were studied after their herbage had been mixed by weight into seven different proportions: 100% alfalfa ‐ 0% orchardgrass, 80% ‐ 20%, 65% ‐ 35%, 50% ‐ 50%, 35% ‐ 65%, 20% ‐ 80%, and 0% ‐ 100%, respectively. The forages were grown in rows of pure alfalfa or pure orchardgrass spaced 45 cm apart on fertilized Dodge silt loam (Typic Hapludalf). Alfalfa was at late bud and orchardgrass was a few days from the appearance of the first anthers when harvested on May 29, 1975. Four replications of each of the mixtures were prepared, and the mixtures were made after tissues had been ground to 40‐mesh size.

No significant differences among mixtures were found for S, Cu, total nonstructural carbohydrates (TNC), or in vitro digestible dry matter (IVDDM). Concentrations of N, P, Ca, Mg, Na, Al, Ba, Fe, Sr, B, Zn, starch, and acid‐detergent lignin (ADL) were highest in pure alfalfa herbage and significantly decreased in concentration as amount of orchardgrass in the mixture increased. In direct contrast, concentrations of K, Mn, total sugars, fructosan, cell wall constituents (CWC), cellulose, hemicellulose, and acid detergent fiber (ADF) were lowest in pure alfalfa herbage and significantly increased in concentration as amount of orchardgrass in the mixture increased. These data show that an increase in amount of orchardgrass in a mixture with alfalfa reduced the concentrations of most herbage constituents important to animal nutrition and increased the fibrous constituents.     

Growth,transpiration, root‐born cytokinins and gibberellins,and nutrient compositional changes in sesame exposed to low root‐zone temperature under different ratios of nitrate: Ammonium supply

The growth of sesame (Sesamum indicum L.) was studied at three root temperature regimes (25/25, 20/10 and 15/15°C day/night) factorially combined with three NO₃ ^‐: NH₄ ⁺ ratios (mM ratios, 10:0, 8:2, or 6:4), as a source of nitrogen (N), in the irrigation solution. The air temperature was kept constant at 30°C. Transpiration, nutrient composition, and level of root‐born cytokinins and gibberellins in the xylem exudate were monitored. The two low root temperature regimes, 15/15 and 20/10°C, restricted the growth of sesame, reduced transpiration and increased the accumulation of soluble carbohydrates in the shoot and in the roots compared to the 25/25°C regime. The NO₃:NH₄ ⁺ ratios had no effect on growth. Nutrient contents in the shoot at low root temperatures, particularly K⁺, NO₃ ^‐, and H₂PO₄ ^‐ were decreased markedly, but Na⁺ increased relative to it's content in the 25/25°C regime. Increasing NH₄ ⁺ proportion in the irrigation solution raised total N concentration in the plant tissues at all root temperatures. The amounts of cytokinins and gibberellins in the xylem exudate decreased at the low root temperature regimes relative to the 25/25°C regime. Low root temperature reduced xylem transport of nutrients and root born‐phytohormones, most probably because of reduced water flow through the plant relative to the 25/25°C regime.     

Growth of apple seedlings on sludge‐amended soils in the greenhouse

Abstract

Open pollinated ‘York Imperial’ apple (Malus domestica Borkh.) seeds were germinated and grown for a period of 7 months in: (1) sand with complete nutrient solutions added; (2) limed and unlimed soil, (3) limed and unlimed soil amended with two different sewage sludges at rates of 25, 50 or 100 dry kg ha^‐1. A third composted, lime stabilized sludge was added either sieved or non‐sieved (to remove wood chips) at the same rates. The sludge materials used were: (1) a high metal, composted sludge from Baltimore, MD (BALT); (2) a high Cd sewage sludge (CITY) and (3) a low metal, composted sewage sludge from Washington, D.C. (DC).

Germination was unaffected by treatments. After 7 months, the best growth was obtained from the sand plus nutrient solution media. Two of the three sludge materials increased seedling growth over that of the soil, either limed or unlimed. The BALT compost treated soils produced the lowest growth, particularly when unlimed. Elevated tissue metal levels indicated that Mn, Zn, Cu and Ni were the probable causes of reduced growth noted from the BALT compost treatment. The use of soil with or without low metal sludges as media for early apple seedling growth when compared to standard sand culture is not recommended.     

Effects of sulfur nutrition on photosynthesis in cadmium‐treated barley seedlings

The effects of sulfur (S) nutrition at 0.1 or 1 mM S on cadmium (Cd) toxicity measured by photosynthesis in barley (Hordeum vulgare L. cv. UC 476) seedlings were studied. Eight‐day‐old seedlings were treated with 25 μM Cd by adding cadmium chloride (CdCl₂) to the nutrient solution. Then photosynthetic carboxylation efficiency (ACi curve) and stomatal conductance of the primary and second leaves were measured at four and eight days after Cd treatment. Fluorescence parameters were measured every 24 h for eight days after two days of Cd treatment. At 20 days, plant growth parameters were measured and dry biomass determined. The results showed that ACi was significantly reduced by Cd, but more in the low (0.1 mM) S than in the high (1 mM) S‐treated plants. Stomatal conductance of plants was also decreased by Cd, but more in the low S‐treated plants. Low S‐treated plants exposed to Cd showed an increase in Fo and Fq, and a decrease in Fv/Fm and T_1/2, indicating photoinhibitory damage to PSII. Analysis of the growth parameters showed that Cd decreased plant size and biomass, but the reduction was more severe in the low S‐treated plants. These results support the hypothesis that S is a critical nutritional factor in plants which is important for the reduction of Cd toxicity.     

Potassium status of some selected soils under different land‐use systems in the subhumid zone of Nigeria

Abstract

Twenty surface soils (0 to 15 cm), selected to represent a wide range of available potassium (K) status and three different land‐use systems (fodder bank, continuously fertilized cropped land and fallow land) across the subhumid zone of Nigeria, were used for the investigation. Laboratory and greenhouse studies were carried out to assess their K status. Available, non‐exchangeable, and total K were determined. The supplying power of the soils was assessed by exhaustive cropping in the greenhouse using Stylosanthes hamata cv. Verano as the indicator plant. While 75% of fodder banks sampled had available K less than 0.20 cmol/kg, only 50% and 13% of continuously fertilized cropped and fallow lands, respectively, had available K less than 0.20 cmol/kg. Potassium weathering coefficient was highest at the lowest exchangeable K and highest [calcium (Ca) + magnesium (Mg)]/K ratio. Total K ranged from 2.30 to 47.06 cmol/kg, with available K forming 1.47% of the total K. The amount of non‐exchangeable K released and taken up by stylo plant accounted for 23.3 to 83.6% of the total K uptake.     

Using Commercially Available Ion‐Exchange Membranes to Monitor Plant‐Available Nutrients in Cranberry

Abstract

Monitoring in‐season nutrient availability in cranberry (Vaccinium macrocarpon Ait.) is hampered by tissue sampling being limited to a short, late‐summer period, and a low‐pH, high‐iron (Fe) soil environment limits soil‐test result interpretation. To evaluate monitoring available in‐season nitrogen (N), phosphorus (P), and potassium (K), commercially available ion‐exchange membranes (PRS?) were placed in plots where standard fertilizer practices were supplemented with the controlled‐release fertilizer (CRF) Osmocote? 14–14–14 at 0, 112, 224 or 336 kg/ha rates. PRS? nitrate (NO₃)‐N was related only to CRF fertilizer, whereas PRS? ammonium (NH₄)‐N reflected both the CRF and in‐season fertilizer applications. Large increases in PRS? NH₄‐N with increasing CRF rates suggested a synergistic effect of CRF on fertilizer NH₄‐N availability. PRS? P was positively correlated with CRF P but negatively to in‐season P applications, whereas PRS? K was related to in‐season fertilizer applications but not to CRF, suggesting poor plant P availability in the soil environment and relatively little K contribution from CRF, respectively. These results show promise for using PRS? in cranberry.     

Increases in phosphatase and β‐glucosidase activities in wheat seedlings in response to phosphorus‐deficient growth

The ability of plants to utilize P efficiently is important for crops growing in P‐deficient soils or on soils with a high P‐fixing capacity. The purpose of this work was to investigate early physiological changes which occur when wheat (Triticum aestivum L.) seedlings were grown under P‐deficient conditions. Wheat plants were grown in a greenhouse and watered with nutrient solution containing or lacking P. During the interval 12 to 18 days after planting, the dry weight of wheat seedlings was similar regardless of P treatment, although the P‐deficient plants had a greater proportion of the total plant weight in the roots. Sixteen days after planting, the roots and leaves of P‐deficient plants had only 20 to 30% the P content of P‐sufficient plants. After 16 days, plants grown under P stress had 41% more p‐nitrophenol phosphatase activity and 70% more β‐glucosidase activity in shoot homogenates than was found in P‐sufficient plants. Changes in both enzyme activities may be involved in the mobilization of plant resources during the early stages of P‐deficient growth.     

Adding selenium‐enriched plant tissue to soil causes the accumulation of selenium in alfalfa

Greenhouse experiments were conducted to determine selenium (Se) uptake by alfalfa (Medicago sativa L.) grown in soils amended with Se‐laden mustard plant tissue. The experimental design was a completely randomized block with treatments consisting of 5, 10, 20, and 40 g of added dried Se‐containing mustard tissue to the soil, which resulted in soil Se concentrations of 1.0, 1.6, 3.0, and 5.7 mg Se/kg, respectively. Four clippings of alfalfa were made and the vegetative portions analyzed for dry weight and total Se. Plant dry weight yields and heights of plants were significantly reduced only at the highest Se treatment rate. Mean tissue Se concentrations increased from 1.8 mg Se/kg DM at the 5 g treatment rate to 6.0 mg Se/kg DM at the 40 g treatment rate. Based on this study, alfalfa can accumulate Se during establishment year when Se‐laden mustard plant tissue is added to the soil.     

Effect of temperature on EDTA‐extractable copper in soils

Abstract

Two contrasting soils were extracted with 0.05 M EDTA in 1 M CH₃ COONH₄ at pH 6, before and after incubation for 4 weeks at constant (10, 20 or 30°C) or fluctuating (10/30, mean 20°C) temperatures. Less copper was extracted from soils which were incubated at fluctuating temperature than from those maintained at a constant 20 C. Where incubation temperature was constant, extractable copper increased or decreased with increasing temperature depending on the soil and how it was treated. Recovery of added copper was low initially but increased during the incubation. Maximum recovery was associated with low incubation temperature in one soil, but high temperature in the other. The amounts of copper extracted were slightly increased by γ‐irradiation of the soils. Extractable copper was also increased by increasing the temperature at which the extraction was performed.     

Humus quantity and quality of an entic Haplustoll under different soil‐crop management systems

Abstract

The effects of different management systems on the level and composition of humified organic matter in an entic Haplustoll from the semiarid Pampean region were studied. The systems were: TPc, wheat‐mixed pasture; TV, wheat (Triticum aestivum), oat (Avena sativa), corn (Zea mays) and triticale grasses; TP, wheat‐cattle grazing; and V, virgin, non cultivated. Humic acids were extracted, fractionated, and analyzed for their organic carbon (OC) content, elemental composition, and E4:E6 spectral ratios. The infrared (IR), electron spin resonance (ESR). and ¹³C‐NMR spectra were registered on these humic acids. The TP rotation showed the lowest humic acid‐carbon to fulvic acid‐carbon (HA‐C:FA‐C) ratio. The lower O:C ratio of humic acids from the cropped soils indicates a higher level of oxidation than that of the virgin one. The comparison of the different methodologies allowed us to conclude that crop rotations and conservation tillage were adequate to mantain the level and composition of the soil organic matter and humus which affected the soil fertility and level of productivity