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1.
Government regulations and public pressure have resulted in the use of composting as an alternative waste handling system for dairies. Utilization of locally-produced manures by vegetable production operations may increase crop yields with less conventional fertilizer. Despite its ability to stabilize nutrients and lower manure volume, composting has costs in time and equipment, so some growers prefer using uncomposted manure. Dairy manure compost at 22 (LC), 45 (MC), or 90 (HC) Mg·ha?1 or uncomposted dairy lot scrapings at 45 Mg·ha?1 (DL) were tilled into soil before seeding a dryland muskmelon (Cucumis melo L.) crop. All plots, including an unamended control (UC), were fertilized with a total of 23N-14P-0K (kg·ha?1). After removal of the cantaloupe in late summer, a drip irrigated broccoli (Brassica oleracea var.botrytis Mill.) crop was planted into the identical plots, and sidedressed with 112 kg·ha?1 N. Muskmelon yields from DL, LC, MC, HC, and UC plots were 9.6, 6.9, 4.1, 9.0, and 2.9 Mg·ha?1, respectively. Broccoli yields from DL, LC, MC, HC, and UC plots were 4.2, 3.6, 4.4, 4.1, and 2.2 Mg·ha?1, respectively. All rates of compost or manure increased yields of cantaloupe, and the subsequent broccoli crop. Use of the manure resulted in highest increase in potential net income from sales of muskmelon and broccoli.  相似文献   

2.
Abstract

The contribution of biological nitrogen fixation (BNF) to the N nutrition of six annual forage legumes, subterranean clover (Trifolium subterraneum), burr medic (Medicago polymorpha), balansa clover (Trifolium michelianum), Persian clover (Trifolium resupinatum), yellow serradela (Ornithopus compressus), and pink serradela (Ornithopus sativus) was evaluated by the 15N natural abundance technique, using four grass species (Briza máxima, Bromus mollis, Hordeum berteroanum, Avena barbata) and two composite species (Leontodon leysseri and Hedipnois cretica) as reference plants. An additional objective was to determine whether alternative legume species to those in common use (T. subterraneum and M. polymorpha) in the area, could improve BNF. The field studies were conducted in two edaphic conditions, granitic (Entisol) and clay (Vertisol) soil, located in Cauquenes, VII Region, in the sub-humid Mediterranean zone of Chile. In the granitic soil the percentages of N derived from fixation were high in all species (74 to 94%); yellow serradela cv. Tauro presented the greatest N content in dry matter and N fixation, equivalent to 91 kg N ha?1. In contrast, pink serradela cv. Cádiz and subterranean clover cv. Gosse presented the lowest N fixation. In the clay soil, under periodically waterlogged conditions, balansa clover cv. Paradana and persian clover cv. Prolific had high percentage values of BNF (>95%) and fixed more N (100.2 and 82.5 kg N ha?1, respectively) than burr medic and subterranean clover cv. Gosse. The present study allowed the identification of new germplasm of high capacity of N fixation which is an additional criterion for selecting species for infertile and waterlogged soil conditions in the Mediterranean area of Chile.  相似文献   

3.
Abstract

Up to 50% of nitrogen (N) fertilizer can remain in soil after crop harvest in dryland farming. Understanding the fate of this residual fertilizer N in soil is important for evaluating its overall use efficiency and environmental effect. Nitrogen-15 (15N)-labeled urea (165 kg N ha?1) was applied to winter wheat (Triticum aestivum L.) growing in three different fertilized soils (no fertilizer, No-F; inorganic nitrogen, phosphorus and potassium fertilization, NPK; and manure plus inorganic NPK fertilization, MNPK) from a long-term trial (19 years) on the south of the Loess Plateau, China. The fate of residual fertilizer N in soils over summer fallow and the second winter wheat growing season was examined. The amount of the residual fertilizer N was highest in the No-F soil (116 kg ha?1), and next was NPK soil (60 kg ha?1), then the MNPK soil (43 kg ha?1) after the first winter wheat harvest. The residual fertilizer N in the No-F soil was mainly in mineral form (43% of the residual 15N), and for the NPK and MNPK soils, it was mainly in organic form. The loss rate of residual 15N in No-F soil over summer fallow was as high as 48%, and significantly (P < 0.05) higher than that in the NPK soil (22%) and MNPK soil (19%). The residual 15N use efficiency (RNUE) by the second winter wheat was 13% in the No-F soil, 6% in the NPK soil and 8% in the MNPK soil. These were equivalent to 9.0, 2.0 and 2.2% of applied 15N. The total 15N recovery (15N uptake by crops and residual in 0–100 cm soil layer) in the MNPK and NPK soils (84.5% and 86.6%, respectively) were both significantly higher than that in the No-F soil (59%) after two growing seasons. The 15N uptake by wheat in two growing seasons was higher in the MNPK soil than in NPK soil. Therefore, we conclude that a high proportion of the residual 15N was lost during the summer fallow under different land management in dryland farming, and that long-term combined application of manure with inorganic fertilizer could increase the fertilizer N uptake and decrease N loss.  相似文献   

4.
Cereal grain and nitrogen (N) fertilizer prices have varied greatly in recent years. The aim of this study was to determine the optimum dose of N fertilizer needed to maximize revenues of soft red winter wheat in Alava (northern Spain). Economically optimum rates of N application (Nyield) ranged from 142 to 174 kg N ha?1 depending on the price of both N fertilizer and wheat. Growers received an extra income of 0.006 [euro] kg?1 if the grain protein content was greater than 12.5%, with the minimum required N dose to obtain this value (Nprot) being 176 kg ha?1. The extra amount of N fertilizer required over Nyield to reach Nprot ranged from 2 to 34 kg N ha?1, and the extra benefits associated varied from 24 to 36 [euro] ha?1.  相似文献   

5.
Quantitative measurements of plant growth characteristics, forage production, nitrogen (N) fixation, and soil N accumulation by white clover were determined in a field experiment at the subhumid hilly region of Rawalakot, Azad Jammu and Kashmir (AJK). Three indigenous and two exotic ecotypes of white clover were used in the study. Indigenous ecotypes were collected from three different locations (i.e., Tollipir, Banjosa, and Rawalakot), whereas exotic ecotypes (NuSiral and Irrigation) were collected from New South Wales Agricultural Research and Advisory Station, Australia. Data were collected for two seasons (spring 2004–autumn 2004). Total average values for height, number of stolons, length of stolons, number of leaves, and leaf area were 13–50 cm, 9–20, 2–4 cm, 23–81, and 7–16 cm2, respectively. The morphological characteristics of exotic ecotypes were significantly higher than the indigenous ecotypes, and the percentage increase in different plant characteristics was +6% to 214%. Total herbage dry‐matter yield (DMY) in the indigenous and exotic ecotypes varied between 0.5–2.3 and 3.6–4 Mg ha?1, respectively. All the ecotypes showed substantial nodulation potential, and the number of nodules in plant roots ranged from 65 to 119, confirming the presence of indigenous Rhizobium population in the soil. The N contents of harvested herbage of white clover were 2.3–3.0% compared to 0.85% in the grass, and the estimated rates of N2 fixation were 26 kg N ha?1 in the indigenous to 79 kg N ha?1 in the exotic ecotypes. Amount of N2 fixed was strongly correlated with DMY, suggesting that crop DM can be used as an indicator of N2 fixation in white clover. Protein content of white clover was 14–19%, compared to 5% in the indigenous grass species. Total organic carbon (C) and N in control soil were 8.5 and 0.75 g kg?1, which increased significantly to 13.1 and 0.93 g kg?1 in soil under white clover. It is concluded that white clover has substantial potential for growth and establishment in the subhumid hilly regions and can be used to recuperate degraded soils because of its ability to sustain high level of pasture production and increase the N status of soil. These benefits could be of particular use for small‐scale resource‐poor farmers.  相似文献   

6.
Brazil is a major world coffee producer, using increasing quantities of nitrogen (N) fertilizer as the monoculture expands across the savannas. The fate and efficiency of this fertilizer N were evaluated for one complete cropping cycle using 15N tracer, permitting an N balance at harvest. Annual rates of 200, 400, 600, and 800 kg N ha?1 year?1 of 15N-labeled urea and an unfertilized control were applied every 14 days via fertigation. The N concentration, percentage of N derived from fertilizer, quantity of N derived from fertilizer, and percentage of nitrogen derived from fertilizer per N rate was assessed for 8-year-old coffee trees. The most efficient N use was with 200 kg ha?1 year?1 because it presented the lowest losses and highest N recoveries in the crop. Conversely, the least sustainable rate was 800 kg ha?1 year?1, which presented the greatest losses and the lowest N recovery in the whole plant.  相似文献   

7.
This study provides current data on plant nitrogen (N) uptake required for maximum sugar yield (PNUpmax) and the corresponding fertilizer N dose (ND) (optimum N dose [NDopt]) for high-yielding beet crops (sugar yield up to 20 Mg ha?1). In 2010 and 2011, field experiments were conducted with four cultivars from Beta genus differing in dry matter composition, and six mineral NDs (0–200 kg N ha?1) at three sites (The Netherlands, Germany, Denmark). Differences between cultivars in PNUpmax and NDopt were small; however, environments (defined as combination of site and year) substantially differed from each other: highest PNUpmax and lowest NDopt occurred at environments supplying high amounts of N from soil resources, and vice versa. The level of maximum sugar yield (SYmax) was related neither to PNUpmax (200–270 kg N ha?1) nor to NDopt. However, N dose and plant N uptake required for 95% of maximum sugar yield was 50–80 kg N ha?1 lower than for maximum sugar yield. To conclude, accepting a slight reduction in sugar yield might allow for a substantial decrease in the ND. Cultivar choice and yield level need not to be taken into account at present.  相似文献   

8.
Abstract

A field study with maize (Zea mays L.) was conducted in the 1988/89 cropping season to investigate the fate of 15NO3-N-labelled NH4 15NO3 applied at 40, 80 and 120 kg N ha?1 (unlabelled N applied at 0, 80, 160 and 240 N ha?1) with and without lime. The investigations were conducted in northern Zambia at Misamfu Regional Research Centre, Kasama on a Misamfu red sandy loam soil. The experimental design was a split plot arrangement with four replications with main plots receiving 0 and 2 Mg ha?1 dolomitic limestone, while subplots received fertilizer N at various rates. Significant (p < 0.001) grain and DM yield responses to applied N up to 160 kg ha?1 were observed. At higher rates little or no crop responses were observed and fertilizer use efficiency declined. Partitioning of amounts of total N and 15N in plants was in the order of seed = tassel > leaf> cob = earleaf> stem. Fertilizer N rates showed a highly significant (p < 0.001) effect on plant uptake of labelled N. Lime and its interaction with N rates had no effect on all measured parameters. Leaching of NO3-N fertilizer to lower soil depths was in proportion to the rate of N applied, with highly significant (p < 0.001) differences among soil depths. Although higher concentrations of fertilizer-15N were recovered in the 0–20 cm depth the recovered portion at lower soil depths was still significant. Total recovery of labelled N by plant and by soil after crop harvest averaged 75, 55 and 54% of originally applied fertilizer-15N at 40, 80 and 120 kg N ha?1, respectively. Corresponding unaccounted for 15N was 25, 45 and 46%. The most probable loss mechanism could have been by leaching to depths greater than 60 cm, gaseous losses to the atmosphere and root assimilation.  相似文献   

9.
Nutrient recycling should be effective at balancing nutrient flows in Japanese animal production. This means replacing imported feed with self-produced feed. The Yakumo Experimental Farm of Kitasato University has produced commercial beef under ‘organic’ management, without the use of agricultural chemicals or imported feed, since 2005. Using a data set obtained from 220 ha of grassland and 250 head of cattle over the 5 years from 2008 to 2012, we estimated nitrogen (N) flow. During 2011 and 2012, we measured grass production, cattle production (selling out), soil parameters and atmospheric deposition (from precipitation and atmospheric ammonia concentrations). To determine N fixation by clover (white clover, Trifolium repens L.), we compared grass + clover plots with grass-only plots. Averaged over the period, N components on the 220 ha of grassland comprised 1952 Mg soil N stock, 3.2 Mg N yr?1 in living livestock, 14.3 Mg N yr?1 uptake by grass growth (including 8.6 Mg yr?1 of N fixed by clover), 15.7 Mg N yr?1 applied in composted manure, 1.7 Mg N yr?1 in imported bedding material, 2.8 Mg N yr?1 in deposition and 1.41 Mg N yr?1 in meat production. N in composted manure equaled about 0.8% of the huge soil N stock; N in grass production equaled about 0.7%, of which clover fixation supplied 60%; N deposition was not negligible; and N export by meat production was minor. These results show that on this organically managed farm, soil N stock increased gradually (by 8.6 Mg N yr?1 [220 ha]?1 = 39 kg N ha?1 yr?1 = 0.02% of the soil N stock) and N export was small. Our findings show that it is possible to balance N inputs with N outputs in a beef cattle enterprise without the need for feed or fertilizer imports.  相似文献   

10.
Abstract

A field experiment was conducted to test the new approach for estimating crop nitrogen (N) uptake from organic inputs. The soil was prelabeled with 15N by applying 15N fertilizer to sunflower crop (Helianthus annuus L. var. Viki). The 14N plots, which received unlabelled fertilizer, were also set up. At harvest, 15N labeled residues were added to the unlabeled soils at a rate of 73 kg N ha?1 (direct technique) and unlabeled residues were added to the 15N‐labeled soils at the same rate (indirect technique). Control plots without residues were also established. All plots were sown with the wheat (Triticum aestivum L. var merchouch)–fababean (Vicia faba L.)–wheat (Triticum aestivum L. var merchouch) cropping sequence.

In the cropping sequence, the first, second and third crop derived respectively 12.01, 2.4, and 1.93 kg N ha?1 from crop residues estimated by the direct method and 14.77, 3.3, and 1.85 kg N ha?1 estimated by the indirect method. The results showed no significant difference between the two techniques, which suggests that the new soil prelabeling technique compares well with the direct technique.  相似文献   

11.
ABSTRACT

Grain protein content is one of the most important quality constraints for bread wheat (Triticum aestivum L.) production in eastern Canada. A field experiment was conducted for two years (1999 and 2000) on the Central Experimental Farm, Ottawa, Canada, to study whether split application of nitrogen (N) fertilizer improved grain protein content and nitrogen-use efficiency (NUE). Two cultivars (‘Celtic,’ as N-responsive and ‘Grandin’, as N-non-responsive) were grown using three different N doses and application methods: (1) 100 kg N ha?1 as NH4NO3, soil-applied at seeding with 15N2-labeled NH4NO3 to microplots, (2) 60 kg N ha?1 soil-applied at seeding plus 40 kg N ha?1 foliar-applied at the boot stage with 15N2-labeled urea to microplots, and (3) 90 kg N ha?1 as soil-applied at seeding plus 10 kg N ha?1 foliar-applied at the boot stage with 15N2-labeled urea to microplots. Plants were sampled at heading and maturity. While dry-matter production and grain yields were not affected by the treatments in either year, N application methods influenced tissue N concentration and NUE. In 1999, extended drought stress led to significant yield reduction; in 2000, foliar application of 10 kg N ha?1 at the boot stage significantly increased grain N concentration when grain protein was under the limit for bread quality, suggesting that later-applied N can contribute to grain protein content. At maturity, the average NUE was 22.3% in 1999 and 34.5% in 2000, but was always greater when all N was applied at seeding (42.5%) than when N was foliar-applied at the boot stage (18.5% to 24.5%). We conclude that application of a small amount of fertilizer N at the boot stage can improve the bread-making quality of spring wheat by increasing grain protein concentration.  相似文献   

12.
Abstract

The logistic model has been used extensively to describe crop response to applied nutrients and water availability. It contains three parameters that can be estimated from data by regression analysis. One of the parameters refers to the reference state of the system, either at zero applied nitrogen (N) or applied N to reach 50% of maximum yield (N 1/2). A negative value of N 1/2 indicates that the soil already contains more than enough N to reach 50% of maximum yield. In the present analysis, data from a field study at Watkinsville, Georgia, which measured response of corn [Zea mays (L.) Pers.] to applied N following plowunder of grass sod is used to verify this point. It was found that N 1/2 shifted from –50 kg ha?1 in the first year to +25 kg ha?1 after several years. Availability of N from decaying vegetation declined exponentially with time. The time constant for decomposition and nitrification was 2 years. Total amount of N released from the vegetation was estimated as 190 kg ha?1.  相似文献   

13.
Excessive nitrogen (N) fertilizer application is common in the central Zhejiang Province area, China. A three-year (2009–11) experiment was conducted to determine the optimum N application rate for this area by studying the effects of various N rates on rice (Oryza sativa L.) yield, N-use efficiency (NUE), and quality of paddy field water. Results showed that no significant yield differences were observed under N rates from 180 to 315 kg ha?1. The NUE could be improved by reducing N application rates without significantly decreasing yield. Due to high ammonia (NH4+-N) and nitrate (NO3—N) concentrations, 5–7 days after N application was a critical stage for reducing N pollution. The N rate for the greatest yield was 176 kg ha?1, accounting for 65 percent of the conventional N rate (270 kg ha?1). The N-rate reduction in this area may be necessary for maintaining high yield, improving NUE, and reducing environmental pollution.  相似文献   

14.
A pot experiment was conducted to determine the effect of four rates of nitrogen (N) in the form of leucaena leaves and the time of application on the performance of sorghum plants using the 15N isotopic dilution technique. Results showed that leucaena green manure (LGM) increased dry matter and N yield of sorghum. Nitrogen recoveries of LGM ranged between 23 and 47%. An additional beneficial effect of LGM was attributed to the enhancement of soil N uptake. The best timing of LGM incorporation for obtaining more N derived from LGM, less soil N uptake, and greater dry matter and N in sorghum leaves seemed to be at planting. However, the appropriate timing and rate of LGM to obtain greater dry matter and N yield in panicles, as well as in the whole plant of sorghum, appeared to be at 30 days before planting, particularly a rate of 120 kg N ha?1.  相似文献   

15.
Swine lagoon sludge is commonly applied to soil as a source of nitrogen (N) for crop production but the fate of applied N not recovered from the soil by the receiver crop has received little attention. The objectives of this study were to (1) assess the yield and N accumulation responses of corn (Zea mays L.) and wheat (Triticum aestivum) to different levels of N applied as swine lagoon sludge, (2) quantify recovery of residual N accumulation by the second and third crops after sludge application, and (3) evaluate the effect of different sludge N rates on nitrate (NO3-N) concentrations in the soil. Sludge N trials were conducted with wheat on two swine farms and with corn on one swine farm in the coastal plain of North Carolina. Agronomic optimum N rates for wheat grown at two locations was 360 kg total sludge N ha?1 and the optimum N rate for corn at one location was 327 kg total sludge N ha?1. Residual N recovered by subsequent wheat and corn crops following the corn crop that received lagoon sludge was 3 and 12 kg N ha?1, respectively, on a whole-plant basis and 2 and 10 kg N ha?1, respectively, on a grain basis at the agronomic optimum N rate for corn (327 kg sludge N ha?1). From the 327 kg ha?1 of sludge N applied to corn, 249 kg N ha?1 were not recovered after harvest of three crops for grain. Accumulation in recalcitrant soil organic N pools, ammonia (NH3) volatilization during sludge application, return of N in stover/straw to the soil, and leaching of NO3 from the root zone probably account for much of the nonutilized N. At the agronomic sludge N rate for corn (327 kg N ha?1), downward movement of NO3-N through the soil was similar to that for the 168 kg N ha?1 urea ammonium nitrate (UAN) treatment. Thus, potential N pollution of groundwater by land application of lagoon sludge would not exceed that caused by UAN application.  相似文献   

16.
In an incubation experiment with flooded rice soil fertilized with different N amounts and sampled at different rice stages, the methane (CH4) and carbon dioxide (CO2) production in relation to soil labile carbon (C) pools under two temperature (35°C and 45°C) and moisture (aerobic and submerged) regimes were investigated. The field treatments imposed in the wet season included unfertilized control and 40, 80 and 120 kg ha?1 N fertilization. The production of CH4 was significantly higher (27%) under submerged compared to aerobic conditions, whereas CO2 production was significantly increased under aerobic by 21% compared to submerged conditions. The average labile C pools were significantly increased by 21% at the highest dose of N (120 kg ha?1) compared to control and was found highest at rice panicle initiation stage. But the grain yield had significantly responded only up to 80 kg ha?1 N, although soil labile C as well as gaseous C emission was noticed to be highest at 120 kg ha?1 N. Hence, 80 kg N ha?1 is a better option in the wet season at low land tropical flooded rice in eastern India for sustaining grain yield and minimizing potential emission of CO2 and CH4.  相似文献   

17.
The aim of this experiment was to investigate the growth and residual‐nitrogen (‐N) effects of different catch‐crop species on a low–N fertility coarse sandy soil. Six legumes (white clover [Trifolium repens L.], red clover [Trifolium pratense L.], Persian clover [Trifolium resupinatum L.], black medic [Medicago lupulina L.], kidney vetch [Anthyllis vulneraria L.], and lupin [Lupinus angustifolius L.]), four nonlegumes (ryegrass [Lolium perenne L.], chicory [Cichorium intybus L.], fodder radish [Raphanus sativus L.], and sorrel [Rumex Acetósa L.]), and one mixture (rye/hairy vetch [Secale cereale L./Vicia villosa L.]) were tested in a field experiment with three replicates in a randomized block design. Four reference treatments without catch crops and with N application (0, 40, 80, and 120 kg N ha–1) to a succeeding spring barley were included in the design. Due to their ability to fix N2, the legume catch crops had a significantly larger aboveground dry‐matter production and N content in the autumn than the nonlegumes. The autumn N uptake of the nonlegumes was 10–13 kg N ha–1 in shoots and approx. 9 kg ha–1 in the roots. The shoot N content of white clover, black medic, red clover, Persian clover, and kidney vetch was 55–67 kg ha–1, and the root N content in white clover and kidney vetch was approx. 25 kg ha–1. The legume catch crops, especially white and red clover, seemed to be valuable N sources for grain production on this soil type and their N fertilizer–replacement values in a following unfertilized spring barley corresponded to 120 and 103 kg N ha–1, respectively. The N fertilizer–replacement values exceeded the N content of shoots and roots.  相似文献   

18.
Maintaining and/or conserving organic carbon (C) and nitrogen (N) concentrations in the soil using management practices can improve its fertility and productivity and help to reduce global warming by sequestration of atmospheric CO2 and N2. We examined the influence of 6 years of tillage (no-till, NT; chisel plowing, CP; and moldboard plowing, MP), cover crop (hairy vetch (Vicia villosa Roth.) vs. winter weeds), and N fertilization (0, 90, and 180 kg N ha−1) on soil organic C and N concentrations in a Norfolk sandy loam (fine-loamy, siliceous, thermic, Typic Kandiudults) under tomato (Lycopersicon esculentum Mill.) and silage corn (Zea mays L.). In a second experiment, we compared the effects of 7 years of non-legume (rye (Secale cereale L.)) and legume (hairy vetch and crimson clover (Trifolium incarnatum L.)) cover crops and N fertilization (HN (90 kg N ha−1 for tomato and 80 kg N ha−1 for eggplant)) and FN (180 kg N ha−1 for tomato and 160 kg N ha−1 for eggplant)) on soil organic C and N in a Greenville fine sandy loam (fine-loamy, kaolinitic, thermic, Rhodic Kandiudults) under tomato and eggplant (Solanum melogena L.). Both experiments were conducted from 1994 to 2000 in Fort Valley, GA. Carbon concentration in cover crops ranged from 704 kg ha−1 in hairy vetch to 3704 kg ha−1 in rye in 1999 and N concentration ranged from 77 kg ha−1 in rye in 1996 to 299 kg ha−1 in crimson clover in 1997. With or without N fertilization, concentrations of soil organic C and N were greater in NT with hairy vetch than in MP with or without hairy vetch (23.5–24.9 vs. 19.9–21.4 Mg ha−1 and 1.92–2.05 vs. 1.58–1.76 Mg ha−1, respectively). Concentrations of organic C and N were also greater with rye, hairy vetch, crimson clover, and FN than with the control without a cover crop or N fertilization (17.5–18.4 vs. 16.5 Mg ha−1 and 1.33–1.43 vs. 1.31 Mg ha−1, respectively). From 1994 to 1999, concentrations of soil organic C and N decreased by 8–16% in NT and 15–25% in CP and MP. From 1994 to 2000, concentrations of organic C and N decreased by 1% with hairy vetch and crimson clover, 2–6% with HN and FN, and 6–18% with the control. With rye, organic C and N increased by 3–4%. Soil organic C and N concentrations can be conserved and/or maintained by reducing their loss through mineralization and erosion, and by sequestering atmospheric CO2 and N2 in the soil using NT with cover crops and N fertilization. These changes in soil management improved soil quality and productivity. Non-legume (rye) was better than legumes (hairy vetch and crimson clover) and N fertilization in increasing concentrations of soil organic C and N.  相似文献   

19.
A field experiment was carried out to study the effect of different rates of potassium (K) fertilizer [0, 50, 100, and 150 potassium oxide (K2O) ha–1] in the presence of increased supply of nitrogen (N) (120, 180, and 240 kg N ha–1) on cotton (Gossypium hirsutum L.) yield and the N and K use efficiencies using the 15N isotopic dilution technique. Potassium fertilizer increased cotton yield, which was significant and more pronounced with the application of N in the high level (N3). The greatest cotton yield (6442 kg ha–1) was obtained in N2K3 treatment with an increase of 14% over the control. In addition, K fertilizer significantly increased N uptake efficiency in the N2 and N3 treatments. The greatest N uptake efficiency (98%) was in N2K3 treatment. The greatest K uptake efficiency (42%) was occurred in N3K1 treatment. In conclusion, the use of K fertilizer could be useful when growing cotton in soils of moderate to high N content to improve N uptake efficiency and consequently increase cotton yield.  相似文献   

20.
Baby spinach is a relatively new crop of commercial significance in South Africa with considerable health attributes. Three parallel trials to investigate its response to nitrogen (N), phosphorus (P), and potassium (K) were conducted. N and P (0, 45, 75, 105, and 120 kg·ha?1) and K (0, 63, 85, 127, and 148 kg·ha?1) treatments were applied to baby spinach in a randomized block design with four replications. After the parallel trial, NPK combination trial was also done. The biomass yield, chlorophyll content, and leaf area index increased significantly with increase in N and P rates; K had no effect on the yield, chlorophyll content, stomatal conductance, and leaf area index. Yield and chlorophyll content peaked at 75 kg·ha?1 of N/P but growth was best optimized at the NPK combination of 45:45:60 kg·ha?1.  相似文献   

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