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1.
The physic nut tree (Jatropha curcas) is an oilseed species with potential for biodiesel production. We evaluated the effect of soil acidity indices on nutrient uptake for optimal growth in physic nut plants grown on acidic soils under greenhouse conditions. Two soils were used in the experiment. Maximum growth was obtained with the application of 1.05 g lime kg-1 for both soils. Maximum growth of the physic nut plants occurred under the following conditions: pH of water = 6.1, calcium (Ca2+) = 17.0 mmolc kg?1, magnesium (Mg2+) = 5.7 mmolc kg?1, acidity saturation = 10.3%, base saturation = 52.3%, Ca saturation = 36.0%, Mg saturation = 12.0% and potassium (K) saturation = 3.8%. Furthermore, the nitrogen (N) requirement of physic nut trees was shown to be high, and to a lesser degree, Ca and Mg requirements were also high, suggesting that liming is very important in crop cultivation of this species.  相似文献   

2.
Four factorial trials were conducted with yam (Dioscorea rotundata Poir.) at Ibadan, Nigeria from 2013 to 2015, investigating effects of (1) tillage (2) fertilizer (3) intercropping (4) yam plant densities. Yam tuber yields varied between years (2013: 16.44 Mg ha?1; 2014: 10.08 Mg ha?1; 2015 26.61 Mg ha?1). In 2013 neither tillage nor fertilizer affected tuber yields. In 2014 tillage increased yields (+25.4%, P < 0.0001), fertilizer reduced yield (?10.5%; P = 0.0046). In 2015 tillage increased tuber yields by 8.1% (ns), fertilizer application increased yield (+17.5%, P = 0.0017). Across the years, tuber yields increased (P < 0.01) with increasing yam density with a constant increase in 2013 up to the highest density, yet yields leveled out above 14,815 plants ha?1 in 2014 and 2015. Intercropping with maize (66,667 plants ha?1) reduced tuber yield by 42.62% in 2013, 44.52% in 2014 and 30.68% in 2015 (P < 0.01 all years) across all yam densities. Maize grain yield was higher in sole crop in 2 years. Fertilizer increased yields in all years (P < 0.0001). Maize yield had no response to the yam densities. Ridging had a negative effect on grain yield in 2015 (?0.3 Mg ha?1, P = 0.0002). Increasing plant density appears a safe measure to increase yam yields.  相似文献   

3.
《Journal of plant nutrition》2013,36(10):1747-1756
Abstract

Forage production is influenced by such factors as applied nutrients, water availability, and harvest interval (for perennials). Logistic models have been developed for response to single and multiple elements such as nitrogen (N), phosphorus (P), and potassium (K). This analysis focuses on response of Pensacola bahiagrass (Paspalum notatum Flügge) to applied N, P, and K. The multiple logistic model is shown to describe the data rather well. A step-wise procedure is outlined for parameter evaluation. It appears that the model is relatively free of bias. It is concluded that a factorial design of N × P × K = 3 × 3 × 3 is the minimum number of treatments required for the analysis. Plant nutrient uptake data would also enhance the value of the results.  相似文献   

4.
《Journal of plant nutrition》2013,36(10):1757-1777
Abstract

The extended multiple logistic model has been used to describe seasonal dry matter and plant nutrient uptake in response to combinations of applied nitrogen (N), phosphorus (P), and potassium (K) for bermudagrass (Cynodon dactylon L) and tall fescue (F. arundinacea Schreb.). In this article, the model is used to analyze data for bahiagrass (Paspalum notatum Flügge) in an N × P × K = 3 × 3 × 3 factorial experiment at Quincy, FL. A procedure is illustrated for standardizing the model over two of the nutrients in order to focus on response to the third. Estimates are made of applied N, P, and K required to reach 50% of maximum potential yield. Similar calculations are included to achieve 50% of potential maximum plant P and K uptake. The strong sensitivity of plant P and K to applied levels of P and K is described as well.  相似文献   

5.
Eight fly ash samples collected from South African power stations were evaluated for various chemical properties, liming potential and metal species release under incubation. All fly ashes had alkaline pH ranging from 10.97 to 12.75 with much wider variations of electrical conductivity (range 0.46–8.27 dS m?1). Their total P content ranged from 553.3 to 1514 mg P kg?1 and Olsen extractable P from 130 to 345.5 mg P kg?1. Application of two of the fly ashes to three different soils showed a high ability to neutralize acidity, resulting in an average of 41% change in pH after 8 weeks of incubation. Across all three soils, the fly ash incorporation increased extractable P content from a P-deficient level to levels above 25 mg P kg?1 in two of the three soils. Except for Cu, all metal species (Cr, Pb, Ni and Fe) showed significantly (P ≤ 0.05) low extractability under fly ash treated soils compared to the soil alone control. These results suggest that the South African fly ashes studied are effective liming materials and can provide essential elements such as P with minimum risk of soil contamination from metal species release.  相似文献   

6.
The correct nutrition of basil (Ocinum basilicum L.) is important to increase its production and quality; however, few papers have deal with this subject. The aim of this work was to evaluate the effects of omission of individual macronutrients on the growth and nutritional status of basil cultivated in nutritive solution. The treatments consisted of nutrient solutions with nitrogen, phosphorus, potassium, calcium, magnesium or sulfur (N, P, K, Ca, Mg, or S) omissions and a complete solution treatment. The plants were cultivated in 8 L plant pots. Plant height, number of leaves per plant, leaf area, relative chlorophyll index, net photosynthesis rate, stomatal conductance, plant dry matter, concentration levels of macronutrients in the aerial part and root system, and nutritional disorders were all evaluated. Nutrient omission was a limiting factor for plant development, substantially reducing its growth. There was also a considerable decrease in nutrient accumulation when compared to the control treatment.  相似文献   

7.
Macro-nutrients in soybean (Glycine max L. Merr.) have not been extensively researched recently. Concentrations and contents of nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur (N, P, K, Ca, Mg, and S) were determined for three irrigated cultivars grown using the early soybean production system (ESPS) on two soils (a sandy loam and a clay) in the Mississippi Delta during 2011 and 2012. Data were collected at growth stages V3, R2, R4, R6, and R8. No change in macro-nutrients due to soil type or years occurred and modern cultivars were similar to data collected >50 years ago. Mean seed yield of 3328 kg ha?1 removed 194.7 kg N ha?1, 16.5 kg P ha?1, 86.0 kg K ha?1, 17.5 kg Ca ha?1, 9.0 kg Mg ha?1, and 10.4 kg S ha?1. Increased yields over the decades are likely due to changed plant architecture and/or pests resistance, improved cultural practices, chemical weed control, and increased levels of atmospheric carbon dioxide (CO2). Yield improvements by genetically manipulating nutrient uptake appear to be unlikely.  相似文献   

8.
《Journal of plant nutrition》2013,36(12):2321-2341
Abstract

Three field experiments were conducted to investigate the effects of soil‐applied nitrogen (N) on plant chemical composition, nutrient removal, and the use of plant analysis to assess N status of Australian waxflowers. Experiments were conducted in commercial plantings of Chamelaucium uncinatum cultivar Alba and a Chamelaucium hybrid (C. floriferum × C. uncinatum) known locally as Walpole wax, at 3 sites in South Australia. Nitrogen, as ammonium nitrate, was applied at rates up to 160 g plant?1 over several side dressings during the growing season. To assess plant nutrient status, stem tips (25–40 mm long tips of stems) were sampled during the growing season and whole stems at harvest.

Nitrogen concentration in both stem tips and whole stems was sensitive to variations in N supply; however, the magnitude of the effect varied between sampling times and sites. In stem tips sampled during spring, the increase in N concentrations ranged from 19.8% at site 2 to 74.6% at site 1. Nitrogen concentrations in stem tips were consistently greater than concentrations in whole stems. The application of N decreased phosphorus (P) concentrations in whole stems and copper (Cu) concentrations in stem tips and whole stems. There was no consistent effect of applied N on potassium (K), calcium (Ca), magnesium (Mg), boron (B), zinc (Zn), and manganese (Mn) concentrations in either plant part sampled. Nutrient removal by flowering stems, in order from greatest to least, was N > K > Ca > P > Mg > Mn > B > Zn > Cu.

Based on 1800 plants ha?1, it was estimated that for N, P, and K, 121.9, 15.4, 60.1 kg ha?1, respectively, was removed in harvested stems. Based on poor sensitivity, the lack of a sharp transition zone between deficient and adequate N concentrations and the lack of consistent relationships between N concentration in stem tips and yield response, it is concluded that N concentration in stem tips is not a useful indicator of the N status of waxflower plants.  相似文献   

9.
ABSTRACT

Cadmium (Cd) is absorbed and bio-accumulated by cacao (Theobroma cacao L.) trees, resulting in unacceptably elevated levels in cocoa beans, necessitating measures to reduce its uptake from soils. A field experiment, lasting 18 months, was carried out to assess the effectiveness of liming on pH, bioavailability of Cd in soils and its uptake in cacao tissues. The treatments were: (a) control (untreated) and (b) lime-treated trees. Results demonstrated a significant (P < 0.05) increase in the soil pH (lime treated) and a natural fluctuation in pH for the control. For the lime-treated trees, bioavailable Cd levels generally stabilized with no significant change (P > 0.05) compared to the significant (P < 0.05) increase showed by control trees. The Cd levels in the leaves of both treatments decreased, however, the rate of decline in leaf Cd concentrations for lime-treated trees (?0.1378) was 3x faster than control (?0.0497) trees demonstrating the effectiveness of liming.  相似文献   

10.
It is important to develop integrated fertilization strategies for various crops that enhance the competitive ability of the crop, maximize crop production and reduce the risk of nonpoint source pollution from fertilizers. In order to study the effects of mineral nitrogen fertilization and biofertilizer inoculation on yield and some physiological traits of rapeseed (Brassica napus L.) under different levels of sulfur fertilizer, field experiments in factorial scheme based on randomized complete block design were conducted with three replications in 2012 and 2013. Experimental factors were: (1) four levels of chemical nitrogen fertilizer (0, 100, 150 and 200 kg N ha?1), (2) two levels of biofertilizer (with and without inoculation) consisting Azotobacter sp. and Azospirillum sp. and (3) two levels of sulfur application (0 and 50 kg S ha?1). Rapeseed yield, oil content of grains and studied physiological traits had a strong association with the N fertilization, biofertilizer inoculation and sulfur (S) application. Higher rates of N fertilization, biofertilizer inoculation and S application increased the grain yield of rapeseed. In the case of physiological traits, the highest value of relative water content (RWC) was recorded in 100 kg N ha?1 that was statistically in par with 150 kg N ha?1 application, while usage of 150 kg N ha?1 showed the maximum cell membrane stability (CMS). Inoculation with biofertilizer and S fertilization resulted in higher RWC and CMS in rapeseed plants. The chlorophyll content showed its maximum values in the highest level of N fertilization, biofertilizer inoculation and S application. The usage of 200 kg N ha?1 significantly decreased the oil content of rapeseed grains, but the highest grain oil content was obtained from the application of 150 kg N ha?1, Azotobacter sp. and Azospirillum sp. inoculation and S fertilization. It seems that moderate N rate (about 150 kg N ha?1) and S application (about 50 kg S ha?1) can prove to be beneficial in improving growth, development and total yield of inoculated rapeseed plants.  相似文献   

11.
ABSTRACT

Excessive application of animal manure to farmland leads to phosphorus (P) loss into the surrounding water. Manure is incinerated to convert it to P-rich ash as a slow-release P fertilizer. However, the potential P loss and P availability for plants from cattle manure ash (CMA) have not been fully understood. The aims of this study were to determine the P release mechanism from CMA and to propose appropriate application rates that mitigate P loss and increase available P to soil in Fukushima, where the soil is deficient in nutrients after the replacement of cesium-137-contaminated soil with sandy mountain soil. Different P fractions in CMA were sequentially extracted with H2O, 0.5 M NaHCO3, 0.1 M NaOH, and 1 M HCl. Phosphorus contents in different fractions of CMA were in the order of HCl–P > NaHCO3–P > H2O–P > NaOH–P. Water-soluble P release of CMA was also determined by kinetic experiments for 120 h. Results showed that total water-soluble P accounted for a maximum of 2.9% of total P in CMA over 120 h due to recalcitrant P compounds formed through incineration. The Fukushima sandy soil amended with CMA at three application rates, 94, 157, and 314 mg P kg?1 (corresponding to 300, 500, 1000 kg P2O5 ha?1) was incubated for 56 days. Cattle manure compost and KH2PO4 were applied at 157 mg P kg?1 for comparison. Phosphorus release in water and CaCl2 solution from ash-amended soil was significantly lower than those from compost and KH2PO4-amended soil at the same P application rate of 157 mg P kg?1 (p < 0.05). Available P in ash-amended soil, determined by Fe-oxide impregnated strips, was not significantly different from those in compost-amended soil after day 7 and KH2PO4-amended soil on day 56 at the same P application rate. Thus, CMA reduces P losses from soil to the surrounding water while it increases P availability for plants. In comparison of different rates of CMA, P release in water or CaCl2 was significantly greater at 314 mg P kg?1 than at 94 or 157 mg P kg?1, while the percentage of available P to total P was the lowest at the highest application rate (p < 0.05), suggesting that the best application rates were 94 and 157 mg P kg?1 in this experiment.  相似文献   

12.
A field experiment was carried out to evaluate the effect of two whole-crop rice (Oryza sativa L.) cultivars, TULT and Takanari, on methane (CH4) emission in a paddy field fertilized with biogas slurry (BS) at rates of 0 (NF), 100 (BS100) and 300 (BS300) kg nitrogen (N) ha?1, in comparison with chemical fertilizer CF100 (100 kg N ha?1). Takanari produced significantly higher biomass (P < 0.001) than TULT and showed significantly (P < 0.01) lower CH4 emission than TULT. BS applications caused higher CH4 emission (52 ± 27 and 80 ± 19 g m?2 in BS100 and BS300, respectively) than did CF100 (42 ± 18 g m?2) and NF (28 ± 10 g m?2) in TULT. In contrast, there was no significant difference in CH4 emission in Takanari among the treatments (26 ± 2, 26 ± 2, 32 ± 4, 29 ± 8 g m?2 in NF, CF100, BS100 and BS300, respectively). Methane oxidizing bacteria (MOB) showed significantly (P < 0.05) higher populations in Takanari than in TULT at harvest, which might be due to the higher root biomass (10.3 ± 2.2 g hill?1) in Takanari than in TULT (8.9 ± 1.8 g hill?1). MOB was significantly correlated with tiller number (R2 = 0.176*) and plant biomass (R2 = 0.242*). BS application showed higher copper (Cu) uptake in Takanari while it was not high in TULT. In contrast, it showed no difference in zinc (Zn) uptake in both varieties. Uptake of Cu was not different between the two varieties, while uptake of Zn in the grain was higher in TULT than in Takanari. The present study suggests that CH4 emission deriving from BS application in paddy field can be mitigated by selecting an appropriate cultivar, like Takanari. However, care should be taken for heavy metal uptake in selecting cultivars.  相似文献   

13.
Abstract

Greenhouse experiment was conducted to evaluate the effect of arbuscular mycorrhizal fungi (AMF) on plant growth, and nutrient uptake in saline soils with different salt and phosphorus (P) levels. The following treatments were included in this experiment: (i) Soil A, with salt level of 16.6 dS m?1 and P level of 8.4 mg kg?1; (ii) Soil B, with salt level of 6.2 dS m?1 and P level of 17.5 mg kg?1; and (iii) Soil C, with salt level of 2.4 dS m?1 and P level of 6.5 mg kg?1. Soils received no (control) or 25 mg P kg?1 soil as triple super phosphate and were either not inoculated (control) or inoculated with a mixture of AM (AM1) and/or with Glomus intraradices (AM2). All pots were amended with 125 mg N kg?1 soil as ammonium sulfate. Barley (Hordeum vulgar L., cv. “ACSAD 6”) was grown for five weeks. Plants grown on highly saline soils were severely affected where the dry weight was significantly lower than plants growing on moderately and low saline soils. The tiller number and the plant height were also lower under highly saline condition. The reduced plant growth under highly saline soils is mainly attributed to the negative effect of the high osmotic potential of the soil solution of the highly saline soils which tend to reduce the nutrient and water uptake as well as reduce the plant root growth. Both the application of P fertilizers and the soil inoculation with either inoculum mixture or G. intraradices increased the dry weight and the height of the plants but not the tiller number. The positive effect of P application on plant growth was similar to the effect of AM inoculation. Phosphorus concentration in the plants was higher in the mycorrhizal plant compared to the non mycorrhizal ones when P was not added. On the other hand, the addition of P increased the P concentration in the plants of the non mycorrhizal plants to as high as that of the mycorrhizal plants. Iron (Fe) and zinc (Zn) uptake increased with AM inoculation. The addition of P had a positive effect on micronutrient uptake in soil with low level of soil P, but had a negative effect in soil with high level of soil P. Micronutrient uptake decreases with increasing soil salinity level. Inoculation with AMF decreases sodium (Na) concentration in plants grown in soil of the highest salinity level but had no effect when plants were grown in soil with moderate or low salinity level. The potassium (K) concentration was not affected by any treatment while the K/Na ratio was increased by AM inoculation only when plant were grown in soil of the highest salinity level.  相似文献   

14.
Boron (B) requirement and its interaction with liming for eucalyptus plantations in sandy soils of Brazilian Pampa are poorly understood. Aiming to diminish this gap, seedlings of Eucalyptus urograndis were grown in pots with Arenosol fertilized with B at rates 0.0, 1.0, 2.5, 5.0 and 10.0 mg B dm?3, with and without liming. Results of shoot and root dry matter and stem diameter did not evidence the necessity of B fertilization. With the exception of the 1.0 mg B dm?3+lime, all other B-fertilized treatments promoted visual symptoms of toxicity, which were partially mitigated by liming. Liming exacerbated the B loss by leaching, but after five months, limed soils had higher content of available B and their plants had higher B concentration in shoots and roots. For our conditions, application of ≥2.5 mg B dm?3 can cause serious toxic injuries to plants and enlarge dramatically the B losses leaching.  相似文献   

15.
To evaluate the effect of seed and nitrogen rates on weed species composition, density, biomass and diversity in two sesame (Sesamum indicum L.) varieties, a field experiment was conducted in 2009, 2010 and 2011 rainy seasons at Samaru, Nigeria. Four seed rates, 2, 4, 6 and 8 kg ha?1, four nitrogen rates, 0, 30, 60 and 90 kg N ha?1 and two sesame varieties NCRIBEN 01M and E8 were arranged as factorial in a split plot design. Weeds with the highest important values in sesame field were Dactyloctenium aegyptium, Ludwigia decurrens, Ageratum conyzoides and Cyperus esculentus. Year had a significant effect on weed density, biomass, diversity, evenness and richness. Weed density, biomass, diversity and richness were lowest in the 2011 trial and weed species evenness in 2009. Variety E8 reduced weed biomass better than NCRIBEN 01M. Averaged over years, weed diversity and evenness were lowest at 4 kg seeds ha?1. Seed × nitrogen rates effect of 4 kg seed ha?1 and 30 kg N ha?1 produced the lowest weed species diversity and evenness. The result suggests that variety E8 at 4 kg seed ha?1 and 30 kg N ha?1 with hoe weeding at 3 and 6 WAS may provide better weed control, and it is recommended in sesame production.  相似文献   

16.
《Journal of plant nutrition》2013,36(7):1295-1317
Abstract

A field experiment was conducted at Central Cotton Research Institute, Multan, Pakistan on Miani soil series, silt loam soil (Calcaric, Cambisols and fine silty, mixed Hyperthermic Fluventic Haplocambids) to assess the response of four cotton (Gossypium hirsutum L.) cultivars to potassium (K) fertilization. The treatments consisted of four cotton cultivars (CIM-448, CIM-1100, NIAB-Karishma, S-12), four potassium rates (0, 62.5, 125, 250 kg K ha?1), and two sources of potassium fertilizer [muriate of potash (KCl) and sulphate of potash (K2SO4)]. The cotton cultivars differed significantly in response to various potassium fertilizer levels and its sources with respect to seed cotton yield and its components. The highest yield was obtained with the application of 250-kg K ha?1, however, it was economical to add 125 kg K ha?1. Seed cotton yield of cv. CIM-448 was considerably greater than that of the other cultivars in K-unfertilized treatments, which was related to cultivar differences in K uptake efficiency in utilizing native potassium nutrient. Potassium added as muriate of potash caused a significant depression in seed cotton yield than that of sulphate of potash. The increase in yield seemed to have resulted largely from the higher K concentration of leaf tissues at bloom stage and available soil-K because of potassium application. A significant relationship between the yield and number of bolls per plant (r = 0.92**) and boll weight (r = 0.85**) indicated that these two growth attributes were responsible for enhancing the quantum of final harvest of seed cotton.  相似文献   

17.
ABSTRACT

Root exudate is derived from plant metabolites and its composition is affected by plant nutrient status. A deficiency of mineral nutrients, such as nitrogen (N) and phosphorus (P), strongly affects the type and amount of plant metabolites. We applied a metabolite profiling technique to investigate root exudates of rice plants under N and P deficiency. Oryza sativa was grown in culture solution containing two N levels (0 and 60 mg N L?1) or two P levels (0 and 8 mg P L?1). Shoot extracts, root extracts, and root exudates were obtained from the rice plants 5 and 15 days after transplanting and their metabolites were determined by capillary electrophoresis/time-of-flight mass spectrometry. Shoot N concentration and dry weight of rice plants grown at ?N level were lower than those of plants grown at +N level. Shoot P concentration and dry weight of rice plants grown at ?P level were lower than those of plants grown at +P level. One hundred and thirty-two, 127, and 98 metabolites were identified in shoot extracts, root extracts, and root exudates, respectively, at the two N levels. One hundred and thirty-two, 128, and 99 metabolites were identified in shoot extracts, root extracts, and root exudates, respectively, at the two P levels. Seventy-seven percent of the metabolites were exuded to the rhizosphere. The concentrations of betaine, gamma-aminobutyric acid, and glutarate in root exudates were higher at both ?N and ?P levels than at their respective high levels. The concentration of spermidine in root exudates was lower at both ?N and ?P levels than at their respective high levels. The concentrations of the other metabolites in root exudates were affected differently by plant N or P status. These results suggest that rice roots actively release many metabolites in response to N and P deficiency.  相似文献   

18.
A 4-year (2008–2009 to 2011–2012) study was conducted on the effect of mineral phosphorus (P) + sulphur (S) and biofertilizers on rain-fed chickpea (Cicer arietinum L.) at the Punjab Agricultural University’s Research Station, Ballowal Saunkhri, India. The experiment comprised of five combinations of P and S, viz. control (P0S0), no P + 10 kg S ha?1 (P0S10), 15 kg P + 10 kg S ha?1 (P15S10), no P + 20 kg S ha?1 (P0S20) and 30 kg P + 20 kg S ha?1 (P30S20); and three seed inoculation levels, viz. control, Rhizobium and phosphate-solubilizing bacteria (PSB), were laid out in randomized complete block design. Combined application of P + S resulted in improved growth, nodulation, yield attributes and yield. The increase in seed yield over control due to P + S ranged from 11.8% to 17.7%. Seed inoculation with Rhizobium recorded the highest growth, nodulation, yield attributes and yield of chickpea and was statistically at par with PSB and significantly better than no inoculation. Highest benefit/cost ratio (B:C, 2.19) was obtained in P30S20. In view of environmental pollution and high costs of chemical fertilizers, biofertilizers alone or in combination may help to achieve sustainable and ecological agricultural production.  相似文献   

19.
Abstract

To develop an advanced method for estimating nitrous oxide (N2O) emission from an agricultural watershed, we used a closed-chamber technique to measure seasonal N2O and nitric oxide (NO) fluxes in cornfields, grassland, pastures and forests at the Shizunai Experimental Livestock Farm (467 ha) in southern Hokkaido, Japan. From 2000 to 2004, N2O and NO fluxes ranged from –137 to 8,920 µg N m?2 h?1 and from –12.1 to 185 µg N m?2 h?1, respectively. Most N2O/NO ratios calculated on the basis of these N2O and NO fluxes ranged between 1 and 100, and the log-normal N2O/NO ratio was positively correlated with the log-normal N2O fluxes (r 2 = 0.346, P < 0.01). These high N2O fluxes, therefore, resulted from increased denitrification activity. Annual N2O emission rates ranged from –1.0 to 81 kg N ha?1 year?1 (average = 6.6 kg N ha?1). As these emission values varied greatly and included extremely high values, we divided them into two groups: normal values (i.e. values lower than the overall average) and high values (i.e. values higher than average). The normal data were significantly positively correlated with N input (r 2 = 0.61, P < 0.01) and the “higher” data from ungrazed fields were significantly positively correlated with N surplus (r 2 = 0.96, P < 0.05). The calculated probability that a high N2O flux would occur was weakly and positively correlated with precipitation from May to August. This probability can be used to represent annual variation in N2O emission rates and to reduce the uncertainty in N2O estimation.  相似文献   

20.
Wheat (Triticum aestivum L.) residues and nitrogen (N) management are the major problems in the southern part of Iran where irrigated wheat–cotton (Gossypium hirsutum L.)–wheat rotation is a common practice. A 2-year (2009–2011) field experiment was conducted as a split plot design with four replications at a cotton field (Darab), Fars Province, Iran, to determine the influence of different rates of wheat residue (0%, 25%, 50%, and 75%) incorporation and N rates (150, 200, 300, and 400 kg ha?1) on weed suppression, yield, and yield components of cotton. Results showed that a higher residue incorporation and a lower N rate improved weed suppression in both years. For treatments receiving 150 kg N ha?1 and 75% of wheat residues (2250 kg ha?1), weed biomass and density were significantly lower compared to treatments receiving 400 kg N ha?1. The highest cotton lint yield (about 2400–2700 kg ha?1) was obtained by 300 kg N ha?1 in the absence of residue application, in both years. Incorporation of 25% of wheat residue (750 kg ha?1) and application of 300 kg N ha?1 are recommended to guarantee an optimum level of cotton lint yield and weed suppression in a wheat–cotton–wheat rotation in this region.  相似文献   

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