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1.
Growth and N‐P‐K uptake in pumpkin (Curcubita moschata Poir.) cv ‘Libby‐Select’ were studied in dryland and irrigated culture. In both moisture regimes, maximum rates of dry matter accumulation occurred between the early and mid‐fruiting developmental stages. Higher total dry matter production with irrigated than dryland culture was primarily associated with increased shoot growth. Concentrations of N, P, and K in foliage generally decreased as pumpkin age increased. Irrigated pumpkins in conjunction with higher total vegetative dry matter accumulated more N, P, and K than dryland pumpkins. Up through early fruit development, N, P, and K accumulation was primarily in leaves and vines and by the late growth stages was almost entirely in the fruit. Total N, P, and K uptake at late fruiting was estimated at 219, 32, and 228 kg/ha in irrigated pumpkins and 180, 21, and 177 kg/ha in dryland pumpkins. Approximately 58% of the N, 52% of the K, and 68% of the P accumulated by late‐fruiting was absorbed by the plant after the early‐fruiting stage in both moisture regimes. Potassium redistribution from vegetative tissues during late fruit development decreased foliar K contents 32% in dryland pumpkins and 21% in irrigated pumpkins.  相似文献   

2.
Abstract

The objective of this study was to determine the effects of pH and ionic strength on the distribution and speciation of zinc (Zn), copper (Cu), and cadmium (Cd) in surface soil samples from two Brazilian Oxisols amended with biosolids. Soils and biosolids were equilibrated in an experimental dual‐chamber diffusion apparatus that permits the soils and biosolids to react through a solution phase via diffusion across a membrane. After equilibrium was reached, soil and biosolids samples were sequentially fractionated to identify various solid forms of Zn, Cu, and Cd. Metal concentrations in the solution phase were determined and mass balance calculated. Equilibrating pH had no major effect on Cu solubility from biosolids and, at pH range from 4 to 7, most Cu remained in the biosolids. Soluble Zn and Cd concentration increased with decreasing pH because of the increased solubility of the biosolids. Copper and Zn were primarily associated with the residual fraction and Fe oxides in one soil, but were primarily associated with chemically unstable fractions, or adsorbed to the surface of oxides, in the other soil. In both soils, Cd was primarily associated with readily bioavailable fractions. The effect of pH on the metal distribution was more evident than the ionic strength effect. Free ions were the predominant metal species in solution, especially at lower pH values.  相似文献   

3.
Annual plants may partition carbon (C) preferentially to reproductive structures slowing root elongation and subsequent nutrient uptake. Although foliar applications of nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) supplement uptake by roots, soybean [Glycine max (L.) Merr.] yield increases have not been found in most studies. Experiments were designed to determine if foliar applications of boron (B), magnesium (Mg), or B+Mg would increase soybean yield and if soybean would respond to B applied to the soil several weeks prior to planting. Foliar B or Mg applied separately four times during reproductive growth did not affect soybean yield. However, four foliar applications of B+Mg increased soybean yield 12% at Mt. Vernon and 4% at Columbia over a three‐year period. Two foliar applications of B+Mg during the late reproductive stages increased soybean yield 8% over a two‐year period. The yield increase from foliar B+Mg treatment resulted from an increased number of pods on the main stem (18%) and branches (44%). A 2.8 kg/ha B application to soil eight weeks prior to planting increased soybean yield 11% during the first year and 13% the second year but had no effect on soybean yield by the third year after application. When results from the first two years were combined, 2.8 kg/ha B applied to soil increased the number of pods per branch by 17% and the number of branch pods per plant by 39%. Foliar applications of B+Mg increased soybean yield in four of six site‐years in the three‐year experiments at two locations.  相似文献   

4.
Abstract

Distribution of dissolved (DOC) and soil organic carbon (SOC) with depth may indicate soil and crop‐management effects on subsurface soil C sequestration. The objectives of this study were to investigate impacts of conventional tillage (CT), no tillage (NT), and cropping sequence on the depth distribution of DOC, SOC, and total nitrogen (N) for a silty clay loam soil after 20 years of continuous sorghum cropping. Conventional tillage consisted of disking, chiseling, ridging, and residue incorporation into soil, while residues remained on the soil surface for NT. Soil was sampled from six depth intervals ranging from 0 to 105 cm. Tillage effects on DOC and total N were primarily observed at 0–5 cm, whereas cropping sequence effects were observed to 55 cm. Soil organic carbon (C) was higher under NT than CT at 0–5 cm but higher under CT for subsurface soils. Dissolved organic C, SOC, and total N were 37, 36, and 66%, respectively, greater under NT than CT at 0–5 cm, and 171, 659, and 837% greater at 0–5 than 80–105 cm. The DOC decreased with each depth increment and averaged 18% higher under a sorghum–wheat–soybean rotation than a continuous sorghum monoculture. Both SOC and total N were higher for sorghum–wheat–soybean than continuous sorghum from 0–55 cm. Conventional tillage increased SOC and DOC in subsurface soils for intensive crop rotations, indicating that assessment of C in subsurface soils may be important for determining effects of tillage practices and crop rotations on soil C sequestration.  相似文献   

5.
Both enzymatic activities increased under B‐deficient and B‐toxic treatments. The ortho‐diphenolic content did not change with B levels.

Our results suggest that the primary B action on the OPP pathway is at the first enzyme (glucose‐6P‐dehydrogenase) level and that the B effect on 6P‐gluconate‐dehydrogenase is secondary to this. The B action on the enzymatic activities seems not to be caused by any direct interaction with substrates, as B infiltration of B‐deficient culture “in vivo”; seems to result in long term effects on cell structures and/or processes not easily r

In this paper the glucose‐6P‐dehydrogenase and 6P‐gluconate ‐ dehydrogenase activities and ortho‐diphenolic content of hydroponically‐cultivated sunflower‐leaves with moderately deficient, normal and toxic B levels were measured. The change in these parameters during time was considered, together with the restoration of enzymatic activities by means of borate infiltration of deficient and normal leaves. The micronutrient content of the leaves was alsversible by B infiltration of leaves. The positive correlation found between the 6P‐gluconate‐dehydrogenase activity and the Zn content in leaves might be interpretable as and indirect B effect on that activity through modification of Zn content.  相似文献   

6.
The suitability of loss‐on‐ignition (LOI) as an alternative to direct measurement of organic carbon (OC) has been debated for decades without resolution. The literature contains an abundance of different linear regression models to describe the LOI–OC relationship, most based on untransformed values of LOI and OC. Such regression is suspect because the variables are unable to occupy Euclidean space. Logratio transformation—based on relative rather than absolute differences—eliminates this constraint. Re‐analysis of the relationship on new and 10 previously published datasets using logratio techniques reveals that the relationship is nonlinear and that the profusion of regression models is in part a function of the range of LOI. Although LOI may offer a crude estimate of OC at high LOI levels, OC/LOI ratios when LOI is less than about 25% are too variable for reliable OC estimation, and interstudy comparisons remain dubious. Direct measurement of OC is recommended.  相似文献   

7.
Sorghum [Sorghum bicolor (L.) Moench cv RTX430, SC214, SC574, SC599, TAM428, and SC326xSC103] were grown on soils of pH 4.2 or 6.2–6.5. Leaf and nonexserted juvenile panicle tissues were collected at 75 days after planting. Fresh and dry weights were measured and element contents [sulfur (S), phosphorus (P), magnesium (Mg), calcium (Ca), potassium (K), zinc (Zn), iron (Fe), and copper (Cu)] were measured by atomic absorption. Significant cultivar differences in ion concentration (μmol/g dry weight) were found. Juvenile panicles had higher ion concentration (μmol/g dry weight) [S, P, Mg, Ca, K, Zn, and Cu) than leaves. Within leaf tissue, ion concentration (μmol/g dry weight) was correlated with tissue water content (g water/g dry weight).  相似文献   

8.
Abstract

About 35% of soils in Venezuela are acid and low in available phosphorus (P). To solve this problem farmers lime and apply phosphate fertilizers to the soils, but both lime and fertilizers are expensive. A good alternative to overcome soil acidity is the use of aluminum (Al)‐tolerant cultivars. The objective of this study was to test the hypothesis, by use of a pot experiment, that sorghum cultivars tolerant to Al toxicity are able to use P from phosphate rock more efficiently than are susceptible cultivars. Three sorghum (Sorghum bicolor L. Moench) cultivars, Chaguaramas III (Ch), AI‐tolerant, Decalb D59 (D59), and Pioneer 8225 (Pi), both Al‐susceptible, were grown in the greenhouse for 20 and 35 days in two acid soils fertilized with 0 and 100 mg P kg‐1 as triple superphosphate (SP) and Riecito phosphate rock (PR). Santa Maria soil was very low in available P (2 mg kg‐1) and highly saturated in Al saturation (64.5%) and Pao soil was higher in available P (20 mg kg‐1) and low in Al saturation (6.5%). Chaguaramas dry matter production, P uptake and root length was higher in Santa Maria soil as compared with Pi and D59 when grown with both SP and PR fertilization. Chaguaramas response to PR in Pao soil was not as good as in Santa Maria soil. The results of our experiment suggest that Al‐tolerant Ch is able to utilize P from PR more efficiently in soils like Santa Maria than Al‐susceptible cultivare Pi and D59.  相似文献   

9.
Abstract

Knowledge of the distribution of soil organic matter (SOM) fractions is important in managing soils toward a sustainable agricultural system in a tropical environment. However, data on Histosols is limited. This study developed 19 profiles of Histosols and soils with high organic-matter content from different regions of Brazil. Soil organic matter was fractionated into fulvic acids (FAF), humic acids (HAF), and humin (HUM). The ratios HAF/FAF and AE (alkaline extract)/HUM were calculated. The objectives were to evaluate the method for SOM fractionating in Histosols and related soils and to correlate the distribution of organic fractions with other soil attributes. The humic fractions presented significant correlations with other soil attributes, the best being the correlation between FAF and nutrient level. The HAF and HUM presented high correlation with cationic exchange capacity, active acidity (H+) and pH. Humin and the alkaline extract absorbance measured at 380 nm and 465 nm and presented good correlation with total organic carbon.  相似文献   

10.
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.  相似文献   

11.
Abstract

Loss‐on‐ignition (LOI) is a simple method for determining ash content, and by reciprocation, organic matter content of compost and manure. However, reported ignition temperatures and heating times for LOI measurements vary widely, and this brings into question the accuracy of one specific combination of ignition temperature and heating time over another. This study examined the effect of 42 temperature‐heating time combinations (six ignition temperatures from 400 to 650°C in 50°C increments by seven heating times of 1, 2, 8, 12, 16, 20, and 24‐h) on the ash content of a finished compost and a fresh manure. The experiment included the 550°C for 2‐h method recommended in Test Methods for Evaluation of Compost and Composting. The magnitude of the decrease in ash content due to increase in temperature was not consistent across all heating times. For example, after a 1‐h heating time for compost, ash content was 75.7% at 400°C and 67.5% at 650°C, compared to 69.6% at 400°C and 66.8% at 650°C after 24‐h. Irrespective of heating time, an ignition temperature of 400°C overestimated ash content for both compost and manure compared to the TMECC method. The TMECC method with its moderate temperature and short heating time requirement could reduce energy costs without affecting ash content results.  相似文献   

12.
Abstract

Individual soil tests are used to assess plant nutrient element needs. Separate soil tests, however, are time consuming and costly. Our objective was to develop a 0.5M sodium bicarbonate (NaHCO3) soil phosphorus (P) test in combination with 0.005M diethylenetriaminepentaacetic acid (DTPA) so macronutrient dements: ammonium‐nitrogen (NH4‐N), nitrate‐nitrogen (NO3‐N), P, potassium (K), calcium (Ca), and magnesium (Mg); and micronutrients: iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) could be quantified in one extraction. The NaHCO3‐DTPA extracting solution is a combination of 0.5M NaHCO3 and 0.005M DTPA and has a pH of 7.60±0.05. Sodium in the solution enhances the NH4, K, Ca, and Mg extraction; bicarbonate (HCO3) is for P extraction; DTPA chelates Ca, Mg, and micronutrients; and the water is for NO3 extraction. Soil samples (0–15 cm depth) came from two sources. The first set was from 12 N x P dryland proso millet (Panicum miliaceum L.) experiments, conducted from 1985 through 1987 in eastern Colorado. These soils were extracted with potassium chloride (KCl), NaHCO3, ammonium acetate (CH3‐COONH4), DTPA, ammonium bicarbonate DTPA (AB‐DTPA), and with the NaHCO3‐DTPA solutions. The second set included 25 soils from Alabama, Georgia, North Carolina, and South Carolina and were analyzed only for available P with the NaHCO3 and NaHCO3‐DTPA methods. Simple linear correlations for macronutrient elements and micronutrients were highly significant. Critical levels for the macronutrient elements: NO3‐N, P, and K were 27, 11, and 144 mg kg‐1, respectively; and the critical levels for the micronutrients: Fe, Mn, Zn, and Cu were 3.9, 0.35, 0.97, and 0.24 mg kg‐1, respectively.  相似文献   

13.
The critical leaf and the threshold values of leaf color chart (LCC) and chlorophyll meter (SPAD‐502) for cassava have been evaluated. The nitrogen (N) rates and cultivars had a significant effect on LCC score, SPAD values, and leaf N concentration of leaf 1 in most cases. Among the three leaf positions studied, the youngest fully expanded leaf (YFEL) blade (leaf 1) had significant, positive correlation of tuber yield with LCC score, SPAD value, and leaf N concentration. The regression between LCC score and leaf N concentration of leaf 1 was LCC = 0.358 (Leaf N) + 0.78 (r2 = 0.81) and that between LCC score and SPAD value was SPAD = 10.981 (LCC) – 3.51 (r2 = 0.82). A threshold LCC score of 2.65 and threshold SPAD value of 25 were suitable to determine the optimal timing of N top‐dressing for cassava.  相似文献   

14.
Abstract

Castor and sunflower, drought‐tolerant crops, are cultivated in the semi‐arid tropics of the world. The nutrient‐rich residues of these crops are mostly burnt because of their high C/N (C/N)‐ratios. These high C/N‐ratio residues can be composted and recycled successfully, if they are supplemented with other low C/N‐ratio farm‐based organics and some chemical additives. To study the rate kinetics and half‐life of decomposition of castor (C/N ratio: 75∶90) and sunflower (C/N ratio 57∶47) residue mixtures and the manure value of the compost thus prepared, two on‐farm experiments were conducted at Hayathnagar Research Farm (17° 18′ N latitude, 78° 36′ E longitude, and an elevation of 515 m above sea level) of Central Research Institute for Dryland Agriculture, Hyderabad, India. The decay rate constants obtained on the basis of the exponential functions using the data on weight loss, C concentration, and C/N ratios indicated that among the four combinations of treatments, castor stalks+gliricidia loppings+cattle dung had the fastest rate of decomposition with an average rate constant value of 0.0043 day?1. To achieve 50% decomposition (half‐life), the time periods computed for castor stalks+gliricidia loppings+cattle dung and sunflower stalks+gliricidia loppings+cattle were 197 and 278 days, respectively. On an average basis, sunflower‐based manure contained a significantly higher amount of total N (14.6 gm kg?1) than castor‐based manures (12.2 gm kg?1). The corresponding total hydrolyzable N values were 8.2 and 8.15 gm kg?1, respectively. Amino acid N was found to be the predominant constituent of the total acid hydrolyzable N in the manure. Use of earthworms in composting enriched the manure in terms of mineral [nitrate (NO3)+ammonium (NH4)‐N] and hexosamine‐N fractions. The full article deals with the decomposition patterns (periodical changes in weight loss, C concentration and C/N ratios), decay‐prediction functions, composting, and manure quality of the castor‐ and sunflower‐based residue mixtures.  相似文献   

15.
Abstract

The extractant Mehlich‐1 is routinely used in Brazil for determination of soil nutrients, whereas Mehlich‐3 has been suggested as a promising extractor for soil fertility evaluation. Both were used for extraction of molybdenum (Mo) in Brazilian soils with Mo dosage by the KI+H2O2 method. The Langmuir and Freundlich isotherms were used to study soil Mo adsorption. Mehlich‐1 extracted more Mo than Mehlich‐3 in soils with high contents of organic matter, clay, and iron (Fe) oxides. Mehlich‐3 and Mehlich‐1 extractions correlated positively and significantly with amorphous Fe oxides, crystalline Fe oxides, and organic matter. Molybdenum recovering rates correlated to crystalline Fe oxides and clay contents but not to organic matter, pH, and Mo adsorption capacity. Amorphous and crystalline Fe oxides, clay, and organic matter were responsible for most of the Mo adsorption. The Langmuir isotherm described better the Mo adsorption to soil amorphous Fe oxides and organic matter than the Freundlich isotherm.  相似文献   

16.
Abstract

Nitrate‐nitrogen concentration in fresh petiole sap, as measured by a portable, battery‐operated, nitrate‐selective electrode, was highly correlated with NO3‐N concentration in dry petiole tissue of broccoli [Brassica oleracea L. (Italica group), r2 = 0.84], celery [Apium graveolens L. var. dulce (Mill.) Pers., r2 = 0.88], lettuce (Lacluca saliva L., r2 = 0.77), pepper (Capsicum annuum var. annuum L., r2 = 0.89), tomato (Lycopersicon esculentum Mill., r2 = 0.83), and watermelon [Citrulius lanatus (Thunb.) Matsum. & Nakai, r2 = 0.88]. This relationship was linear over a wide range of NO3‐N values and was generally unaffected by site, crop, cultivar, or growth stage, provided that petiole tissue analyzed was from recently matured leaves. Sap was analyzed directly without dilution or filtration. The slope of the regression equation differed widely among crops. Selective electrode analysis of NO3‐N concentration of soil solution samples obtained by suction lysimetry was also highly correlated with conventional laboratory technique (r2 = 0.87). The nitrate‐selective electrode appeared to be a useful tool for on‐farm monitoring of soil and crop N status.  相似文献   

17.
Abstract

A laboratory experiment evaluated the rate of urea hydrolysis and ammonia volatilization from urea (U) mixed in organo‐mineral (O‐M) fertilizers. These fertilizers were incubated in soil in the presence or absence of N‐(n‐butyl)thiophosphoric triamide (NBPT) as a urease inhibitor. Two organic matrices, leather (L) and peat (P), were used to prepare the O‐M fertilizers. In the absence of NBPT, the highest ammonia losses and the fastest rate of urea hydrolysis were in the soil treated with the fertilizer containing leather (UL50). Significantly lower ammonia losses occurred with peat‐based fertilizers. Although the fertilizer containing peat (UP50) stimulated the rate of urea hydrolysis with respect to the urea alone, no increase in ammonia volatilization was detected. NBPT‐containing fertilizers were stored for different times (0,7, 30, and 60 days) and temperatures (25°C and 40°C), and the NBPT recovery was monitored by extraction and analysis by HPLC. The NBPT recovery decreased by increasing either the storage time or the storage temperature. Differences among the fertilizers occurred after storage at 40°C for 30 or 60 days. With UN, in spite of about 25% extracted amount of NBPT, the ammonia losses did not increase with respect to the non‐stored fertilizer. On the contrary, no inhibitor was recovered from either of the O‐M fertilizers (UNL and UNP). However, in the presence of leather, NBPT reduced the volatilization losses by 35 to 40%, whereas in the presence of peat, a complete loss of NBPT efficiency occurred. In general, either the inhibitor recovery or efficiency were affected by the storage conditions or the type of organic matrix.  相似文献   

18.
Abstract

Effect of incubation and microbial inhibition at field capacity level on changes in DTPA‐extractable Mn in acidic, neutral, and alkaline soils was examined. Incubation decreased and microbial inhibition increased the level of Mn in soils with high pH (>5.7) and high microbial activity. The change was apparently partially associated with microbes since the level of Mn did not change in soils with low microbial activity and/or low pH.  相似文献   

19.
Abstract

Long‐term effects on plant and soil‐profile chemical composition imposed by a residential sewage sludge were studied on an Oxisol from Hawaii. Sludge was applied at 0, 45, 90, and 180 Mg/ha in 1983. An NPK‐fertilized treatment was included for comparison. Sudangrass (Sorghum bicolorL. Moench) was grown as a test crop in the 1983–84 and 1986–87 seasons. Soil samples for chemical analysis were taken in 1987 at three depths: 0–23 cm, 23–46 cm, and 46–69 cm.

Beneficial effects of sludge, measured 3 years after application (beginning of the 1986's planting), were evident by large yield increases on sludge‐amended soils relative to the unamended and the NPK‐fertilized soils. The first cutting produced approximately 5 Mg/ha of dry matter from the sludge treatments, regardless of rate, as compared with 3 and 1.5 Mg/ha from the NPK and the 0 treatments. Regrowths showed similar effect, though less dramatic; average yields were 2.6 Mg/ha with sludge and 1.6 Mg/ha without.

Heavy‐metal concentrations in plants were generally unaffected by sludge applications; probably because (i) heavy‐metal contents of the sludge were low, and (ii) soil pH was increased by sludge.

Remarkable increases in pH, exchangeable Ca and extractable P, and resultant decreases in exchangeable Al, in all three soil layers of sludge‐amended soils suggest that surface application of a low heavy‐metal sludge could serve to correct subsoil acidity and enhance subsoil P availability.  相似文献   

20.
An experiment was conducted with Phalaris aquatica L. cv. Sirolan under hydroponic conditions in the glasshouse at constant temperature of 25°C and natural sunlight. Plants were grown in double pot system with four sulfur and three molybdenum levels along with all the major‐ and micro‐nutrient elements. There was increase in growth, nitrate‐reductase activity and contents of most of the nutrient elements at all levels of sulfur and 1.68 μ/L molybdenum. Molybdenum at 3.36 μg/L level inhibited growth and nitrate‐reductase activity and decreased concentration of nutrient elements in plant. The inhibitory effect of higher level of molybdenum is perhaps mediated through its role in the nitrate‐reductase.  相似文献   

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