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1.
The optimal nitrogen (N) rate for cotton (Gossypium hirsutum L.) production in the late 20th century is greater than it was in the middle of the century (112 versus 27 kg ha‐1). Part of the reason for this difference is that modern cultivars exhibit a greater harvest index than obsolete cultivars. This greater harvest index helps to allow modern cultivars to utilize greater N rates. However, factors other than harvest index, such as the development of leaf area in response to N, may also play an important role. Therefore, the objective of this study was to characterize leaf area index (LAI) of four obsolete and four modern cultivars at a low and high fertilizer N level. Cotton was grown in the field for two years (1992 and 1993) with two locations each year. The locations were a Beulah fine sandy loam and a Dubbs silt loam. Two preplant fertilizer‐N rates were used, a low (22 kg N ha‐1) and a high(112 kg N ha‐1). Leaf area index was determined at three stages in each year (early, mid, and late season). Yield was determined at maturity. Averaged across years, locations, and cultivars, late‐season LAI increased from 2.32 at 22 kg N ha‐1 to 3.15 at 112 kg N ha‐1 by late season. In 1992, modern and obsolete cultivars had similar LAI responses to N at early and mid season but by late season, LAI of modern cultivars was greater under high N than the obsolete cultivars (3.53 versus 2.95). Lint yield of the four modern cultivars was 372 kg ha‐1 greater than the four obsolete cultivars at 112 kg N ha‐1 and 289 kg lint ha‐1 greater at 22 kg N ha‐1 in 1992. The LAI response to N level of the modern cultivars was similar to that of obsolete cultivars in 1993 at all three sampling dates. In 1993, the lint yield of modern cultivars was 238 kg ha‐1 greater than obsolete cultivars under 112 kg N ha‐1 and 182 kg lint ha‐1 at 22 kg N ha‐1. In summary, our results best support the hypothesis that the higher yield of modern cultivars at high fertilizer N is unrelated to their LAI.  相似文献   

2.
Abstract

Accurate estimates of cotton (Gossypium hirsutum) dry matter accumulation and nitrogen content are important for both production and environmental reasons. One of the important factors in estimate accuracy is sample size. The objective of this investigation was to determine the cotton sample size necessary for acceptable estimates of cotton dry matter, lint yield, and shoot N per 100 kg of lint ratio (NLR) values. Three cotton cultivars (DeltaPine 90, DeltaPine 5415, and Stoneville 474) were planted on 13 May 1997 in an Eunola loamy sand (fine‐loamy, siliceous, thermic Aquic Hapludult) in 9.3‐m2 subplots of a split‐split plot design. Split plots were four sampling dates. Split‐split plots were four sampling techniques [a) four randomly selected plants (4RP), b) 0.3 meter of row (0.3‐m), c) one meter of row (1‐m), and d) two meters of row (2‐m)]. Each entire subplot was harvested on each sampling date after sampling by the four techniques. Shoot dry matter for the whole plot was 7.2 Mg ha‐1, and lint yield was 1.46 Mg ha‐1. Cotton shoot dry matter and NLRs were significantly overestimated by both the 4RP and 0.3‐m techniques, but not by the 1‐ and 2‐m techniques. The NLRs of cultivar subplots varied with cultivar from 9.1 to 11.4. The earliest maturing cultivar, DeltaPine 90, had the lowest NLR and the latest maturing cultivar, Stoneville 474, had the highest NLR. Accurate estimates of cotton dry matter accumulation and N content will likely require 1‐m samples, and 2‐m samples should further improve precision. The NLRs were similar to data (NLR <15) that suggest 1.6 Mg ha‐1 (3‐bale/acre) cotton lint yields can be achieved with less than 250 kg ha‐1 of shoot‐accumulated N.  相似文献   

3.
Balanced plant nutrition is essential to achieve high yields of canola (Brassica napus L.) and get the best economic return from applied fertilizers. A field study was conducted at nine site‐years across eastern Canada to investigate the effects of nitrogen (N), sulfur (S) and boron (B) fertilization on canola nutrient uptake, nutrient balance, and their relationship to canola yields. The factorial experiment consisted of four N rates of 0 (N0), 50 (N50), 100 (N100), and 150 (N150) kg ha?1, two S rates of 0 (S0) and 20 (S20) kg ha?1, and three B treatments of 0 (B0), 2 kg ha?1 at preplant (B2.0P), and 0.5 kg B ha?1 foliar‐applied at early flowering stage (B0.5F). Each site‐year used the same experimental design and assigned treatments in a randomized complete block design with four replications. Fertilizer S application greatly improved seed yields at six out of nine site‐years, and the highest N use efficiency was in the N150+S20 treatment. Sulfur application generally increased seed S concentration, seed S removal, and plant total S uptake, while B fertilization mainly elevated straw B concentration and content, with minimal effect on seed yields. At the early flowering stage, plant tissue S ranged from 2.2 to 6.6 mg S g?1, but the N : S ratio was over or close to the critical value of 12 in the N150+S0 combination at five site‐years. On average across nine site‐years, canola reached a plateau yield of 3580 kg ha?1 when plants contained 197 kg N ha?1, 33 kg S ha?1 and 200 g B ha?1, with a seed B content of 60 g B ha?1. The critical N, S, and B values identified in this work and their potential for a posteriori nutrient diagnosis of canola should be useful to validate fertilizer requirements for canola production in eastern Canada.  相似文献   

4.
Nitrogen (N) fertilization in rice (Oryza sativa L.) is extensive throughout the world, but fertilizer N recovery is generally low. Split fertilizer applications that coincide with plant demand have been suggested as a method of improving fertilizer N efficiency. However, the effectiveness of split applications has not been established. Furthermore, there is little information available on plant N accumulation after a midseason application. The purpose of this study was to measure plant dry matter, root growth, and N accumulation after a midseason N application and to determine the length of time during which midseason N is accumulated by the plant. ‘Cypress’ rice was drill‐seeded in a Crowley silt loam soil (fine, montmorillonitic, thermic Typic Albaqualf) and urea‐N was broadcast at 101 kg N ha‐1 preflood. Microplots enclosed by retainers were established prior to panicle initiation (PI), and l5N‐labeled urea was topdressed at PI into the floodwater within each microplot at 67 kg N ha‐1. Microplots were harvested at 1 day after topdress (DAT), 3 DAT.7DAT, 14 DAT, and at 90% heading (35 DAT). Dry matter production was not affected by the midseason N application and increased linearly from the time of midseason application until 90% heading. Root growth at the time of the midseason application was extensive and roots could be seen at the soil surface. Root length density was greatest in the top 7.5 cm of the soil profile and decreased with depth. Most accumulation of midseason N occurred within 7 DAT. Both midseason N and native N in the plant increased during this period. About half of the midseason N was accumulated by the crop, probably because of the extent of the root system. This approximates N recovery from preplant or preflood N applications. Nitrogen loss was probably due to ammonia (NH3) volatilization. Nitrogen accumulation by the plants continued throughout the duration of the experiment. This study shows that N broadcast into the floodwater at PI is quickly and efficiently utilized.  相似文献   

5.
ABSTRACT

This study was conducted to formulate an in-season nitrogen (N) fertilization optimization algorithm (NFOA) to estimate midseason N rates that maximize corn (Zea mays L.) growth and minimize fertilizer inputs. Treatments included: a zero kg N ha?1; three treatments of 134 kg N ha?1 fixed rate applied in split, preplant, or sidedress; two treatments of 67 kg N ha?1 fixed rate preplant or sidedress applied; three NFOA-based midseason N rates (RI-NFOA, RICV-NFOA, flat-RICV-NFOA) with (67 kg N ha?1) and without preplant N; and two resolutions (0.34 and 2.32 m2) tested for RICV-NFOA only. With the 67 kg N ha?1 preplant application, midseason RI-NFOA-based N rates resulted in an N use efficiency (NUE) of 65% while the 134 kg N ha?1 fixed rate split applied had 56% NUE. Using the RICV-NFOA, NUE and net returns to N fertilizer were higher when spatial variability was treated at 2.32 m2 resolution.  相似文献   

6.
《Journal of plant nutrition》2013,36(7):1183-1197
Abstract

Nitrogen (N) fertilization continues to be of primary importance in the economically successful production of cotton (Gossypium hirsutum L.). Profit margins of producers might be expanded by increasing the uptake efficiency of applied N. Recently, N fertilization of crops grown in the Mississippi River Delta has been suspected to impact water quality in the Gulf of Mexico. Improving efficiency of N uptake could alleviate some environmental concerns by increasing the retention of N at the site of application. The objective of this study was to determine the impact of replacing preplant N applications with postemergent N applications on the growth and yield characteristics of cotton. Delayed applications of the recommended rate of N fertilizer (112 kg N ha?1) were tested for four years under irrigated and dry land production conditions. The N rate was applied either preplant, after crop emergence, or at first square. Further, 112 kg N ha?1 was split applied evenly at preplant + first square, and after emergence + first square. The five 112 kg ha?1 N treatments were compared to an unfertilized control. Yield tended to be maximized with N treatments that included a first square application. Yields were usually lowest in the unfertilized control and the 112 kg N ha?1 preplant treatments. Not surprisingly, both yield and plant growth was influenced more by irrigation than N fertilization. Years when drought conditions caused water stress and limited plant growth, dry land cotton had only limited response to the N fertilization treatments. Irrigated cotton responded to N treatments all years with increased growth and yield. Optimizing agronomic considerations, the best N fertilization timing was an after emergence + first square split application.

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7.
This study reports and analyzes nutrient balances in experimental vegetable production systems of the two West African cities of Tamale (Ghana) and Ouagadougou (Burkina Faso) over a two‐year period comprising thirteen and eleven crops, respectively. Nutrient‐use efficiency was also calculated. In Tamale and Ouagadougou, up to 2% (8 and 80 kg N ha?1) of annually applied fertilizer nitrogen were leached. While biochar application or wastewater irrigation on fertilized plots did not influence N leaching in both cities, P and K leaching, as determined with ion‐absorbing resin cartridges, were reduced on biochar‐amended plots in Tamale. Annual nutrient balances amounted to +362 kg N ha?1, +217 kg P ha?1, and –125 kg K ha?1 in Tamale, while Ouagadougou had balances of up to +692 kg N ha?1, +166 kg P ha?1, and –175 kg K ha?1 y?1. Under farmers' practice of fertilization, agronomic nutrient‐use efficiencies were generally higher in Tamale than in Ouagadougou, but declined in both cities during the last season. This was the result of the higher nutrient inputs in Ouagadougou compared to Tamale and relatively lower outputs. The high N and P surpluses and K deficits call for adjustments in local fertilization practices to enhance nutrient‐use efficiency and prevent risks of eutrophication.  相似文献   

8.
An established two‐year‐old stand of ‘Apollo’ alfalfa (Medicago saliva L.) was used to determine the alfalfa yield and macronutrient contents response to potassium (K), sulfur (S), boron (B), and molybdenum (Mo) fertilization under a high yield environment. A split, split block field design was used with nine micronutrient treatments (0, 50, and 100 g Mo ha‐1 and 0, 1, and 2 kg B ha‐1) in a factorial arrangement (32) as the subplots and three K levels (150, 300, and 600 kg K ha‐1) as the main plot in three replications. Two levels of S (0 and 240 kg S ha‐1) fertilization were applied in strips across the main plots (K levels) resulting in the split, split block design. Alfalfa yield and macronutrient contests were determined. Increased in K or S rate increased K contents of the plants, however, the differences between the K or S rates were not significant and B or Mo application did not have a marked effect on alfalfa K levels. Alfalfa calcium (Ca), magnesium (Mg), or phosphorus (P) content was not significantly affected by K, S, B, or Mo fertilization. Potassium, S, B, or Mo fertilizer application also did not have a marked effect on alfalfa yield during this study. Combinations of K, S, B, and Mo fertilizer had variable effects and the effects were dependent on the combination of fertilizer, sources, and levels. With a few exceptions, there was lack of alfalfa yield and nutrient contents response to K, S, B, and Mo applications which was due to the effect of low available soil moisture as a result of low incident rainfall during the study on these nutrients availability, uptake, and alfalfa growth.  相似文献   

9.
Abstract

Grain deficits frequently occur in the Southeastern Atlantic Coastal Plain because erratic rainfall patterns and soil properties often limit corn (Zea mays L.) yields, however, harvesting corn for silage may enable farmers to produce a second grain crop during the same calendar year. Effects of row spacing, plant population, and fertilizer program on yield, quality, and mineral concentrations of corn silage grown with irrigation on Typic Paleudult soils were therefore investigated. Two plant population treatments which averaged 7.0 and 10.1 plants m‐2 were evaluated with two fertilizer programs that differed in N, N and K, and N, P, and K in 1980, 1981, and 1982, respectively. Each plant density by fertilizer combination was evaluated in single rows spaced 96 cm apart and in twin rows which approximately doubled the intrarow plant spacing. Plot size for the 2×2×2 factorial experiment ranged from 30 to 44 m2. Yield, quality, and mineral concentrations of corn silage grown in single rows spaced 96 or 75 cm apart and twin rows were also evaluated in large (185 m2) plots under center pivot irrigation during 1981 and 1982.

Dry matter yields of 22 to 26 Mg ha‐1 were achieved with plant densities of 6.7 to 13.5 plants m‐2 at both experimental sites. Highest silage yields were produced with stand densities of 9 m or more planted in single 75 cm or twin rows, but yield differences were statistically significant at P(0.05) in only two of five site years. Increasing total N‐P‐K application beyond 200–30–167 kg ha”; increased crude protein slightly in 1980 and significantly in 1981 and 1982. Concentrations of Mn and Zn in silage were increased by higher fertilization, presumably because nitrification reduced surface soil pH and increased their availability. Dry matter yield, fiber, energy, and other mineral nutrients were not significantly influenced by fertilizer program. These experiments identified management practices for the Atlantic Coastal Plain which resulted in corn silage yields equal to those produced in the cooler mountain region of Georgia and that exceeded current average production in South Carolina by approximately 40% without reducing apparent feed quality.  相似文献   

10.
The influence of different fertilization practices [i.e., nitrogen (N), phosphorus (P), and potassium (K) fertilizers, crop residue, and manure] on dry matter production of white yam (Dioscorea rotundata) “kokoro” a late variety of yam, tuber biomass and dry matter distribution to the plant parts was determined in upper Oueme basin (Republic of Benin) in the years 2001, 2002 and 2003. The experimental design was a randomized complete block with four replications. Altogether there were eight plots divided into two groups consisting of four plots each, one was treated with manure (at the rate of 10 ton ha?1), second plot with mineral fertilizer (N30:P30:K60), third plot with combination of manure and mineral fertilizer, whereas the fourth plot was left as control (no application of fertilizer). In year 2002 and 2003 the same combinations were made taking crop residues (at the rate of10 ton ha?1) from external sources as a source of organic matter at the place of manure. Manure application did not have a significant effect on yam total biomass production nor on tuber yield when applied on fields after fallow. Whereas crop residue application had a positive significant effect on yam tuber and total biomass production when applied after cotton and maize and with adequate rainfall amount and distribution. Regarding partitioning pattern in yam crop, no effect of different practices of fertilization has been noticed. The crop behaves identically (i.e, partitioning rate) in both fertilized and unfertilized management practice.  相似文献   

11.
On the basis of long‐term fertilization experiments in Skierniewice, being conducted since 1923 at the Experimental Field of Warsaw Agricultural University, the fate (or balance) of nitrogen for a period of 35 years and that of phosphorus and potassium for 20 years, was studied. The balance includes N, P and K rates applied in mineral fertilizers and farmyard manure (FYM), uptake of these nutrients by the crop plants and the changes in the content of total N and total P and of slow release K in the soil during that time. The nitrogen balance shows a loss of this nutrient of 11—14 kg N ha—1 y—1, which corresponds to 15% of the applied ammonium nitrate on fields without FYM but to 23% on fields with FYM, in spite of crop yields being considerably greater on fields treated with FYM. The phosphorus balance indicated that in the 0—70 cm soil layer less than 4% of P from superphosphate was not found. In the treatment not fertilized with potassium for many years, the plants took up 49 kg K ha—1 y—1 from slow release forms because the fraction of available K did not change during that period. When calculating the potassium balance only 1.6% of K from potash salt were not found in plots without FYM but 12.3% of the applied KCl were not recovered in treatments with FYM. The comparison of the P‐ and K‐uptake from organic and mineral fertilizer in the two crop rotations indicates a higher P‐ and K‐efficiency from FYM than from inorganic fertilizer.  相似文献   

12.
Sugarcane filtercake (a waste by-product of sugarcane processing) compost was evaluated as a partial substitute for inorganic fertilizer in a fresh-market tomato (Lycopersicon esculentum Mill.) crop production system. Plots receiving fertilization rates of 0, 50, or 100% (153N-134P- 280K, kg ha?1) of a typical commercial application were amended with or without compost (188 t ha?1). Tomato (cv. Sunny) seedlings were transplanted in the center of each raised bed. A randomized complete block experimental design was used with the six compost/fertilization treatments replicated four times. Plant height (22 days after transplanting), stem diameter and shoot weight (just after final harvest), fruit yields, and fruit size were measured for each plot. Plants grown with no fertilization were taller (22 days after transplanting) in plots amended with than without compost, but not at 50 or 100% fertilization rates. Plots that were amended with compost had plants with heavier shoots (kg/plant), thicker stems, higher total and early marketable fruit number and weight and larger fruit size than plots not amended with compost, regardless of fertilization rates. These results suggest that sugarcane filtercake compost can serve as a partial substitute for inorganic fertilizer while maintaining or improving tomato fruit yields and size.  相似文献   

13.
ABSTRACT

Crop production in arid regions is characterized with high temperature, drought and salinity which decrease water and nutrient use efficiency. This study was conducted to investigate the effect of wheat residue mulch in relation to N fertilizer application rates for cotton productivity under dryland condition of Uzbekistan. Main plots were control of no mulch addition and a 5 t ha?1 mulch treatment. These plots were split into 5 N rate plots of 0, 70, 140, 210 or 280 kg of N ha?1. The results showed that mulching pattern decreased soil temperature by 0.7–1.5°C as compared to conventional treatment (CT), regardless of N fertilization rates. The soil water storage increased by 41.8, 17.3, 48.0 mm in the flowering, boll formation and ripening stages of cotton, respectively under mulching treatment. Soil available N concentration and nutrients uptake by plants consistently increased with the increase of N fertilization rates with positive correlations. At flowering period, the plant height, chlorophyll content, stem diameter, and a number of fruit branches in plants were higher by 32.3%, 46.8%, 26.7% and 55.3%, respectively at 210 kg N ha?1 under mulching treatment as compared to the non-fertilized control. The highest cotton yield was obtained at 210 kg N ha?1 application under mulching treatment. The correlation difference between mulch and N application rates was higher (R2 = 0.97) than the difference in CTs and N application rates (R2 = 0.89). This study showed that mulching had a greater impact to preserve nutrients and water resources in the soil, thereby improved cotton growth and yield.  相似文献   

14.
Lack of environmentally safe handling of garbage is a growing problem in urban sub‐Saharan Africa (SSA). Composting the garbage for soil‐fertility management presents an opportunity for reducing the risks of environmental pollution. This study aimed at evaluating the agronomic effectiveness and nutrient‐utilization efficiency of urban market crop‐waste compost on a Eutric Ferralsol. The study was conducted in central Uganda with treatments including compost applied at 0, 5, and 10 t ha–1 (d.w. basis); inorganic N fertilizer at rates of 0, 40, and 80 kg ha–1 and inorganic P fertilizer at 0, 9, and 18 kg ha–1. Maize (Zea mays L.), variety Longe 4 was used as the test crop. The nutrient quality of the compost was medium with total N of 0.9% and total P of 0.45%. Compost significantly increased plant height, LAI, stover weight, and grain yield; however, there were no significant differences between the 5 and 10 t ha–1 rates. Nitrogen also had a significant effect on LAI and stover yield, though there was no significant difference between the 40 and 80 kg ha–1 rates. Likewise, P increased plant height with no significant difference between the 9 and 18 kg ha–1 rates. Mineral N at 40 kg ha–1 led to the highest increase in N uptake by plants (76%) above the control. Nitrogen‐ and P‐utilization efficiencies for the 5 t ha–1 compost rate were more than twice that of the 10 t ha–1 rate. The highest P‐utilization efficiency (69%) was obtained where 9 kg ha–1 P was applied with 40 kg ha–1 N, while the highest N‐utilization efficiency (48%) was obtained with the 5 t ha–1 compost applied together with N at 40 kg ha–1. From the above studies, it is clear that effectiveness of the 5 t ha–1 compost rate is the most promising.  相似文献   

15.
The influence of manure and diammonium phosphate (DAP) mineral fertilizer on germination, leaf nitrogen content, nitrate accumulation and yield of vegetable amaranth (Amaranthus hypochondriacus) was investigated. Field trials were set up at the University of Nairobi Field Station at the Upper Kabete Campus during the long rains of March–May in 2007 and 2008. Trials were laid out as complete randomized block design with four fertilization treatments: 20, 40, and 60 kg nitrogen (N) ha?1 supplied by DAP (18:46:0), 40 kg N ha?1 supplied by cattle manure and an unfertilized control variant. The vegetables were harvested at three maturity stages at 6, 7, and 8 weeks after planting. Results indicated that there were significant differences between treatments in germination percentage, leaf nitrogen content, nitrate accumulation and vegetable yield. Plants that received manure had a higher germination percentage than those that received the same amount of N supplied by the chemical fertilizer DAP. The yields generally increased from week 6 to week 8. The highest yield was recorded in plots receiving 40 kg N ha?1 from DAP at eight weeks after planting. Plots that were supplied with manure recorded the lowest yield when compared to the fertilizer treated plots at all rates. Leaf nitrogen content increased with increasing rate of N but only when N was supplied by DAP fertilizer. The leaf nitrogen content decreased with increasing age of the plants. The leaf nitrate content increased with increase in DAP application rate. Results indicate that manure application produced quality vegetables in terms of low nitrate levels, but leaf nitrogen and vegetable yields were low. DAP application effected higher yields, but the vegetables had high though acceptable nitrate levels.  相似文献   

16.
Does net soil nitrogen (N) mineralization change if N‐fertility management is suddenly altered? This study, conducted in a long‐term no‐tillage maize (Zea mays L.) fertility experiment (established 1970), evaluated how changing previous fertilizer N (PN) management influenced in situ net soil N mineralization (NSNM). Net soil N mineralization was measured by incubating undisturbed soil cores with anion and cation exchange resins. In each of three PN fertilizer application plots (0, 84, and 336 kg N ha?1), another three fertilizer application rates (0, 84, and 336 kg N ha?1) were imposed and considered the current fertilizer N (CN) management. Generally, PN‐336 (336 kg N ha?1) had significantly greater NSNM than PN‐0 (0 kg N ha?1) or PN‐84 (84 kg N ha?1), which reflected differences in soil organic‐C (SOC) and soil total‐N (STN). The three CN rates had no significant effect on NSNM when they were applied to PN‐0 or PN‐84, but CN‐336 (336 kg N ha?1) had significantly higher NSNM than CN‐0 (0 kg N ha?1) or CN‐84 (84 kg N ha?1) in the PN‐336 plots. The CN or “added N interaction” used the indigenous soil organic matter (SOM) pool and the added sufficient fertilizer N. Environmental factors, including precipitation and mean air temperature, explained the most variability in average daily soil N mineralization rate during each incubation period. Soil water content at each sampling day could also explain NSNM loss via potential denitrification. We conclude that “added N interaction” in the field condition was the combined effect of SOM and sufficient fertilizer N input.  相似文献   

17.
This study aims to examine the effects of long‐term fertilization and cropping on some chemical and microbiological properties of the soil in a 32 y old long‐term fertility experiment at Almora (Himalayan region, India) under rainfed soybean‐wheat rotation. Continuous annual application of recommended doses of chemical fertilizer and 10 Mg ha–1 FYM on fresh‐weight basis (NPK + FYM) to soybean (Glycine max L.) sustained not only higher productivity of soybean and residual wheat (Triticum aestivum L.) crop, but also resulted in build‐up of total soil organic C (SOC), total soil N, P, and K. Concentration of SOC increased by 40% and 70% in the NPK + FYM–treated plots as compared to NPK (43.1 Mg C ha–1) and unfertilized control plots (35.5 Mg C ha–1), respectively. Average annual contribution of C input from soybean was 29% and that from wheat was 24% of the harvestable aboveground biomass yield. Annual gross C input and annual rate of total SOC enrichment from initial soil in the 0–15 cm layer were 4362 and 333 kg C ha–1, respectively, for the plots under NPK + FYM. It was observed that the soils under the unfertilized control, NK and N + FYM treatments, suffered a net annual loss of 5.1, 5.2, and 15.8 kg P ha–1, respectively, whereas the soils under NP, NPK, and NPK + FYM had net annual gains of 25.3, 18.8, and 16.4 kg P ha–1, respectively. There was net negative K balance in all the treatments ranging from 6.9 kg ha–1 y–1 in NK to 82.4 kg ha–1 y–1 in N + FYM–treated plots. The application of NPK + FYM also recorded the highest levels of soil microbial‐biomass C, soil microbial‐biomass N, populations of viable and culturable soil microbes.  相似文献   

18.
Abstract

Available soil mineral nitrogen (N) varies both temporally and spatially. These variations affect field‐scale N‐use efficiency. A field study was conducted for three years to investigate spatial variability in available soil mineral N within uniform research plots in relation to leaf greenness or chlorophyll content (plant N sufficiency) and yield. Variations within the plot in available soil mineral N sampled at the 6‐ligule stage was related to N fertility: the higher the fertilizer N levels, the higher the variability. The standard deviation for the 200 kg N ha‐1 treatment was up to five times higher than the unfertilized control treatment. The nitrate (NO3)‐N accounted for 70 to 80% of soil mineral N in fertilized plots compared to 50 to 60% in unfertilized control plots. The variability in grain yield of individual maize (Zea mays L.) plants within a plot was inversely related to soil N fertility: the higher the fertilizer N levels, the lower the yield variability (at 100 or 200 kg N ha‐1, yield ranged from 97 to 148 g plant1, or 10% CV within ayear compared to ranges from 0 to 82, or 50% CV in the same year at 0 kg N ha‐1). On an individual plant basis, chlorophyll content from the 6‐ligule stage through the growing season generally showed much smaller CV's, but had a similar trend to variations in yield. Leaf greenness from 6‐ligule stage to silking was significantly correlated with harvest yield (r>0.60, P<0.01), and both also correlated with available soil mineral N, though to a lesser degree (r>0.36). The number of fully expanded leaves prior to silking differentiated N treatments better than did single leaf chlorophyll measurements with higher yields associated with more rapid vegetative development. Our data suggest that multiple core samples are required to estimate available soil mineral N, particularly in fertilized plots that have greater spatial variability. Variability of plant‐based measures, such as chlorophyll content, could be used as an indicator of relative plant N sufficiency at early growth stages as spatial variability declined with higher soil N fertility.  相似文献   

19.
The silk industry is important for south China's rural economy. Leaves of mulberry (Morus spp.) are used for silkworm production. Hubei province is one of the main silk‐producing provinces in China. The objectives of this research were to survey the fertilization practices in the mulberry‐producing regions in the province and to determine the best nutrition‐management practice for mulberry plantations. A survey and a series of field experiments with N, P, K, and micronutrients were conducted from 2001 to 2002. In addition, a silkworm‐growth experiment was also conducted by feeding leaves harvested from various fertilization treatments. The results indicate that poor soil fertility and unbalanced fertilization were the main factors limiting mulberry‐leaf yield and quality in Hubei province. Nitrogen fertilization of mulberry has reached a high level (454 kg ha–1 y–1) in Hubei province, but P‐ and K‐fertilization rates have not been matched with N‐fertilization rates as farmers are not aware of the significance of P and K. Balanced fertilization showed positive nutrient interactions with respect to mulberry yield and quality. Potassium application increased yield and quality (protein and sugar concentration) of mulberry leaves. Silkworm growth and cocoon quality were improved when silkworms were fed with the leaves derived from K‐fertilized plants in comparison with those taken from control plots. Application of Mg, S, and B also significantly improved leaf sugar, essential and total amino acid concentrations, but did not increase leaf yield significantly. It is concluded that a fertilizer dose of 375 kg N ha–1, 66 kg P ha–1, and 125 kg K ha–1 is suitable for the cultivation of mulberry in the Hubei province along with Mg, S, and B, wherever necessary, for the improvement of yield and quality of mulberry leaves.  相似文献   

20.
Oriental tobacco plants (Nicotiana tabacum L. cv Myrodata Agrinion) were grown without nitrogen (N) fertilization (N0) and with added ammonium nitrate at a rate of 50 kg‐ha‐1 (N1) and 100 kg‐ha‐1 (N2). Non‐uniform patterns for leaf FW and DW changes per node showed a decreasing trend from lower to upper nodes during the vegetative stage. From approaching flowering to fruit set, these patterns became more uniform. Plants which were fertilized with N had increased leaf FW and DW accumulation levels and non‐uniform distribution patterns, primarily during the reproductive stage, and leaves of the lower nodes were found in the older plants. By contrast, the median values of leaf FW for the unfertilized plants were reduced during the reproductive period. The DW/FW×100 ratio values revealed a stable relationship between leaf FW and DW from the vegetative to the reproductive stage, while modified patterns of DW/FW×100 appeared later in the plant cycle. Nitrogen fertilization resulted in an early appearance of modified patterns of DW/FW×100 in the plant life cycle and higher accumulation of dry matter per unit leaf area. Patterns of total leaf N concentration showed an increasing trend from the lower to the upper nodes for all plant ages and treatments. Total N concentration values varied from 1.6%, 1.9%, and 1.8% on a dry matter basis, for the lower node up to 5.5%, 6.3%, and 6.1% for the upper node in young tobacco plants in the N o , N1, and N 2 treatments, respectively. After fruit set, a more uniform distribution of total leaf N was observed among the leaves in all treatments. Concentration values for total leaf N in older plants varied from 1.9%, 2.1%, and 2.2% for the lower node up to 3.4%, 3.3% and 3.2% for the upper node in the N 0 , N1, and N2 treatments, respectively. These results suggest a progressive decrease with plant age for total leaf N concentration in the plant as a whole. The increased N fertilizer level affected the total N level in young plants but not in the older ones. Inflorescence and fruit set periods are critical for plant N balance except for the plants which received the increased N fertilization. The determined total stem N concentration was less than that for the leaves. This change in the stem, similar to leaves, showed an increasing trend from the basal to the upper part and a decreasing trend from the vegetative to the reproductive stage. The total stem N level declined from 1.0–1.2%, 1.6–1.7%, and 2.2–2.9% on a dry matter basis to 0.5–0.6%, 1.0–1.2%, and 1.2–1.6% for the basal, middle, and upper part of the stem, respectively.  相似文献   

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