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1.
In order to provide a scientific basis for developing integrated weed management strategies in rice paddy fields, this study investigated the influences of different types of fertilization on weed biodiversity. The experiment was conducted at Long‐term‐located Monitoring Station for Soil Fertility, Agricultural Science Academy, of Jiangxi Province, China. Five fertilization treatments were set: no fertilization (NOF), PK, NP, NK, and NPK. The results showed that the influence of different fertilization treatments on weed community traits followed the models PK > NOF > NK > NP > NPK for species richness, PK > NOF > NK > NP > NPK for species diversity, NPK > NP > NK > NOF > PK for community dominance, and PK > NOF > NK > NP > NPK for community evenness. Under NPK (i.e. balanced fertilization), the weed species diversity and richness and weed community evenness were the lowest. The principal component analysis showed that the weed community was divided into three groups: (i) NK and a part of NOF; (ii) NP and NPK; and (iii) PK and NOF. The correlation analysis indicated that the influence of each macro‐element on the weed community followed the model N > P > K. The organic content in the paddy soil might have played an equally important role with the amount of available N in determining the weed community's characteristics. Regarding the way by which N, P, and K influenced the weed community, the amount of available P and K mainly influenced the organic content, while the amount of available N influenced both the organic content and light transmittance within the canopy, thereby enhancing the capacity of rice to compete with weeds.  相似文献   

2.
Naturally occurring fallow weeds are an alternative strategy for reducing nitrogen (N) loss from annual cropping systems by scavenging inorganic N from the soil. Soil tillage is a major factor affecting the growth of weed populations. This study was carried out to determine the effect of a no‐tillage (NT) system on the N scavenging capacity of fallow weeds in a double‐season rice cropping system. A fixed field experiment was carried out at the Experimental Farm of Hunan Agricultural University, Hunan Province, China, from 2008 to 2011. The results indicated that NT had 80% greater aboveground biomass of fallow weeds than conventional tillage (CT). There was no significant difference in N concentration in fallow weeds between NT and CT. N uptake by fallow weeds was 82% higher under NT than under CT. The stem density of fallow weeds was 50% higher under NT than under CT. The difference in the single‐stem biomass of fallow weeds was not significant between NT and CT. These results suggest that the N scavenging capacity of fallow weeds in the double‐rice cropping system can be increased by increasing the stem density and aboveground biomass through the adoption of NT farming. Our study identifies a potential new ecosystem service provided by NT farming.  相似文献   

3.
In Europe, sugar beet is often produced in a 3‐year rotation with cereals, leaving stubble fields fallow from cereal harvest until primary tillage in autumn in the year prior to sugar beet production. The weed flora on such fields could include host plants of Heterodera schachtii that is one of the most important pests of sugar beet. Crop sequences with non‐hosts and cover cropping with resistant cruciferous hosts during this period have been crucial for its management. Availability of resistant and tolerant sugar beet cultivars could entice growers to forego cover cropping, exacerbating weed problems during the fallow period. The objective of this study was to determine the reproductive potential of H. schachtii on weeds that develop during this period. Under glasshouse conditions, reproduction on 39 plant species was compared with that on oilseed radish and sugar beet of differing nematode host status. In 2 years in field microplots, 18 previously tested species were grown in H. schachtii‐infested soil during the typical fallow period at 60 plants m?2, and nine of these species were also grown at 180 plants m?2. There were variable results between years after 8 weeks of growth, but most weeds allowed lower reproduction (<10%) than the susceptible sugar beet; only Stellaria media at 180 plants m?2 and Thlaspi arvense at both plant densities increased nematodes. Such weed densities may seldom occur under commercial conditions; thus, weed management for nematological considerations during the stubble period may have limited importance.  相似文献   

4.
Two of the many benefits of including legume cover crops in a fallow cropping system are weed suppression and increased soil organic N. This study was conducted in order to examine the effect of hairy vetch (Vicia villosa) on weed growth and soil N through a fallow period in subtropical Okinawa, Japan. Together with an untreated control plot, hairy vetch was grown from November 2007 to April 2008 and subsequently incorporated into the soil. The weeds were allowed to develop uncontrolled for 2 months until the time when a cash crop would be planted. In the period after the incorporation of hairy vetch, the weed biomass in the hairy vetch (HV)+ plot was more than threefold greater than that in the HV? plot. Hairy vetch had a high tendency to uptake N in April before the incorporation of hairy vetch; the N uptake by the weeds was lower in the HV+ plot than in the HV? plot. After the incorporation of hairy vetch, the N uptake by the weeds in the HV+ plot was two‐to‐six times higher than that by the weeds in the HV? plot. The C/N ratios of hairy vetch and the weeds in the HV+ plot were lower than those of the weeds in the HV? plot. More than half of the hairy vetch residue and N in the residue had decomposed by 28 days after incorporation. The content of both the NH4‐N and NO3‐N in the HV+ soil was higher than that in the HV? soil. Moreover, the amount of NO3‐N increased during the growing period of hairy vetch and decreased after the incorporation of hairy vetch. The fallow soil into which hairy vetch had been incorporated displayed a greater weed biomass and resulted in a higher inorganic N content than the soil that had not supported hairy vetch.  相似文献   

5.
A long-term fertilization experiment was set up in northern Xinjiang, China to evaluate the dynamics of crop production and soil organic carbon(SOC) from 1990 to 2012 with seven fertilization treatments. The seven treatments included an unfertilized control(CK) and six different combinations of phosphorus(P), potassium(K), nitrogen(N), straw(S) and animal manure(M). The balanced fertilization treatments had significantly(P0.05) higher average yields than the unbalanced ones. The treatment with 2/3 N from potassium sulfate(NPK) and 1/3 N from farmyard manure(NPKM) had a higher average yield than the other treatments. The average yields(over the 23 years) in the treatments of NPK, and urea, calcium superphosphate(NP) did not differ significantly(P0.05) but were higher than that in the treatment with urea and potassium sulfate(NK; P0.05). The results also show that the highest increases in SOC(P0.05) occurred in NPKM with a potential increase of 1.2 t C/(hm~2·a). The increase in SOC was only 0.31, 0.30 and 0.12 t C/(hm~2·a) for NPKS(9/10 N from NPK and 1/10 N from straw), NPK and NP, respectively; and the SOC in the NP, NK and CK treatments were approaching equilibrium and so did not rise or fall significantly over the 23-year experiment. A complete NPK plus manure fertilization program is recommended for this extremely arid region to maximize both yields and carbon sequestration.  相似文献   

6.
Diversity and weed community composition of mid-season plant stands and autumn seedbanks were examined in spring barley–red clover cropping systems that varied according to crop rotation, tillage and weed management. Weed plant and seed density data collected over 4 years were used in the calculation of species richness (number of species), evenness (Shannon's E) and diversity (Shannon's H′), and in multivariate analysis (canonical discriminant analysis) of weed communities. Weed diversity indices were low (H′ < 2.0) but sensitive to management practices. Evenness had intermediate values (E = 0.4–0.8), suggesting little evidence of truly dominant species, particularly in the seedbanks. The difference in the number of species between treatments was never large (approximately two to four species). Overall, diversity indices were highest in the low disturbance treatments, particularly those with minimum weed management. Factors affecting ordination were somewhat different from those affecting diversity. Tillage had little effect on weed diversity indices but had a more major role in determining weed community composition. Seedbanks in no-till and monoculture-chisel plough treatments appeared to have more distinctive species composition compared with other treatments. Weed species assembly in seedbanks showed little discrimination across treatments and over time, confirming the ability of seedbanks to buffer disturbances across a variety of cropping systems. The use of diversity indices revealed part of the complexity of weed communities associated with disturbance in cropping systems, whereas ordination singled out species–cropping systems associations, which may be more meaningful to weed management.  相似文献   

7.
Multiple herbicide‐resistant (MHR ) weed populations pose significant agronomic and economic threats and demand the development and implementation of ecologically based tactics for sustainable management. We investigated the influence of nitrogen fertiliser rate (56, 112, 168, or 224 kg N ha?1) and spring wheat seeding density (67.3 kg ha?1 or 101 kg ha?1) on the demography of one herbicide susceptible and two MHR Avena fatua populations under two cropping systems (continuous cropping and crop‐fallow rotation). To represent a wide range of environmental conditions, data were obtained in field conditions over 3 years (2013–2015). A stochastic density‐dependent population dynamics model was constructed using the demographic data to project A. fatua populations. Elasticity analysis was used to identify demographic processes with negative impacts on population growth. In both cropping systems, MHR seedbank densities were negatively impacted by increasing nitrogen fertilisation rate and wheat density. Overall, MHR seedbank densities were larger in the wheat‐ fallow compared with the continuous wheat cropping system and seedbank densities stabilised near zero in the high nitrogen and high spring wheat seeding rate treatment. In both cropping systems, density‐dependent seed production was the most influential parameter impacting population growth rate. This study demonstrated that while the short‐term impact of weed management tactics can be investigated by field experiments, evaluation of long‐term consequences requires the use of population dynamics models. Demographic models, such as the one constructed here, will aid in selecting ecologically based weed management tactics, such as appropriate resource availability and modification to crop competitive ability to reduce the impact of MHR .  相似文献   

8.
The aim of this study was to assess the effects of crop management practices on the diversity, structure, and composition of weed communities. A total of 30 fields (15 fields each) in low‐input and conventional farming systems were surveyed in north‐eastern Iran. In the conventional cropping system, both mineral fertilizers and herbicides were applied, while in the low‐input cropping system, the fertilizer was mainly manure and herbicides were avoided. The results showed that the pool of species, species richness, number of unique species, and Shannon's diversity index were greater in the low‐input system than in the conventional system. Both cropping systems had more broad‐leaved species than grasses and more annual species than perennial species. All the multivariate methods of analysis that were applied revealed that the weed community composition was significantly different between the two management types. The low‐input cropping favored herbicide‐susceptible broad‐leaved weeds, legumes, and weeds with biodiversity value, whereas a high proportion of herbicide‐tolerant grasses was found in the conventional fields. The results suggest that low‐input cropping can sustain high weed diversity and abundance.  相似文献   

9.
Crops in shifting cultivation fields often suffer from severe weed infestation when long fallow periods are replaced by short fallow periods. The soil seedbank as a source of weed infestation was studied in four fields that differed in their last fallow duration. The effect of burning was analysed by comparing adjacent pre‐burn and post‐burn samples (two sites). Surface vegetation was monitored from burning to harvest in the plots from which soil samples were taken to determine the fraction of the seedbank germinating (three sites). Seedbank size (1700–4000 seedlings m?2) varied depending on a single species, Mimosa diplotricha. Burning reduced emergence of most species, but stimulated emergence in others. Densities in the seedbank were not correlated with above‐ground abundances in the field, except for some species. Most species emerging after 50 days from the soil samples (40% of seedlings) were absent from the field after 190 days. Whilst the data from this study are derived from only four fields, the weed problems after short‐term fallowing appeared to be due to a larger fraction of the seedbank emerging, possibly due to shallow burial, and to a floristic shift towards adaption to burning, rather than the size of the seedbank per se.  相似文献   

10.
While weeds generally are considered as the most important overarching production constraints in inland‐valley cropping systems in West Africa, little is known about species' associations with environmental and crop management factors. Weed species' associations with seasonal and environmental factors, such as their position on the catena, soils and cropping systems, were studied during two seasons (dry and wet) in 45 arable fields of three inland valleys in south‐western Benin, Africa. The three most dominant weed species were Dactyloctenium aegyptium, Commelina benghalensis and Digitaria horizontalis on the inland‐valley crests (uplands), Ludwigia hyssopifolia, Corchorus aestuans and Ludwigia octovalvis on the sloping hydromorphic fringes and Leersia hexandra, Ipomoea aquatica and Fimbristylis ferruginea in the valley bottoms (lowlands). Echinochloa colona, Cleome viscosa and Talinum triangulare were the three most dominant species in the dry‐season crops (maize or vegetables) and Leer. hexandra, I. aquatica and Sphenoclea zeylanica were the three most dominant species in the wet‐season crop (rice). Ageratum conyzoides, Synedrella nodiflora and D. horizontalis were observed throughout the catena. Problem weeds in inland‐valley agro‐ecosystems are those that combine a high frequency with a high submergence tolerance and ecological plasticity, C4 grasses, perennial C3 species with persistent root structures and broad‐leaved species with high propagation rates. Weed management strategies that are aimed at increasing the resilience of rice‐based cropping systems in the inland valleys of the southern Guinea Savanna of Africa should address the categories of problem species that were identified in this study. This can be done best by following an integrated approach, including the use of more weed‐competitive cultivars and rotation crops.  相似文献   

11.
RODER  KEOBOULAPHA  PHENGCHANH  PROT  MATIAS 《Weed Research》1998,38(3):167-174
Reduced fallow length in slash-and-burn rice (Oryza sativa L.) production systems of northern Laos increased weed pressure, labour requirement and the need for soil and moisture conservation. On-farm and on-station studies and on-farm surveys were used to evaluate the effect of residue management and cropping intensity on weed population, rice yield and nematode density. Residue loads were 2.3–4.4 t ha?1 after a rice crop and 9.5 t ha?1 after 1 year of fallow. Compared with farmers' traditional burning of crop and weed residues, mulching reduced rice yield by 43% in one out of four comparisons and increased weed biomass by 19–100%. Compared with continuous rice treatments (averaged over burning and mulching treatments), treatments with fallow or cowpea [Vigna unguiculata (L.) Walp.] in the previous year had 32% less herbaceous weed biomass, 90% fewer Ageratum conyzoides L. and over 99% fewer Meloidogyne graminicola Golden & Birchfield. Rice yield was negatively associated with A. conyzoides density (?0.62, P < 0.01) and M. graminicola number (?0.42, P < 0.05). Less striking effects of fallow period on A. conyzoides and M. graminicola, observed from on-farm surveys, demonstrate the limitations of on-farm studies because of undocumented effects of farmers' management decisions.  相似文献   

12.
Echinochloa crus‐galli is an important maize weed with significant variation in herbicide sensitivity. This differential response may reflect differences in selection pressure caused by years of cropping system‐related herbicide usage. The herbicide sensitivity of E. crus‐galli populations from three divergent cropping systems was evaluated in dose–response pot experiments. Populations were collected from sandy fields with (i) a long‐term organic cropping system, (ii) a conventional cropping system with maize in the crop rotation or (iii) a conventional cropping system with long‐term monocropping of maize. Each cropping system was represented by six E. crus‐galli populations. The effectiveness of three foliar‐applied maize herbicides (nicosulfuron, cycloxydim and topramezone) and two soil‐applied maize herbicides (S‐metolachlor and dimethenamid‐P) was tested at three doses and two runs. Foliar‐applied herbicides were applied at the three true leaves stage. Soil‐applied herbicides were applied immediately after sowing. The foliage dry weight per pot was determined 4 weeks after treatment. Plant responses were expressed as biomass reduction. Herbicide sensitivity was consistently lowest for populations from maize monocropping systems. Compared with populations from organic cropping systems, populations from monocropping systems showed 6.9%, 9.8% and 29.3% lower sensitivity to cycloxydim, topramezone and nicosulfuron respectively. Populations from the conventional crop rotation system showed intermediate sensitivity levels, which did not significantly differ from sensitivity levels of populations from the other cropping systems. Sensitivity to dimethenamid‐P and S‐metolachlor was not affected by cropping system. Environmental conditions influenced herbicidal response . This study indicated that integrated weed management may be necessary to preserve herbicide efficacy over the long term.  相似文献   

13.
Akobundu  Ekeleme  & Chikoye 《Weed Research》1999,39(3):241-256
The influence of weeds on maize intercropped with cassava was evaluated in three fallow management systems and four cropping frequencies from 1989 to 1996 in Ibadan, Nigeria, West Africa. Fallow management systems consisted of natural bush, Leucaena leucocephala hedgerows and Pueraria phaseoloides fallow. Frequencies of cropping were continuous cropping, 1 cropping year alternating with 1, 2 and 3 years of uncropped fallow. Shrubs and climbers contributed 60–70% and herbs (predominantly weeds) 30–40% to the total dry matter produced in all treatments. Weed dry matter and seedbank increased with time in all treatments but was higher in natural bush fallow by the fifth and sixth years and in continuously cropped plots. Weed seed density increased with time in the continuously cropped plots and in plots cropped after 1 or 2 years of fallow but decreased with time when the fallow period was up to 3 years. Maize grain yield decreased over time in both unweeded and weeded plots irrespective of treatment with the exception of the weeded P. phaseoloides fallow treatment. Cassava tuber yield decreased over time in unweeded plots in all treatments while tuber yield increased in weeded P. phaseoloides fallow treatment and remained relatively constant in L. leucocephala and natural bush fallow plots. The results from this study suggest that planted fallow involving legume species is more effective in weed management in the long term than natural fallow. Fallow period was beneficial to crop yield and yield improvement increased with the length of the fallow cycle, particularly for cassava.  相似文献   

14.
Plasmodiophora brassicae, causal agent of clubroot of crucifers, poses a serious threat to Canadian canola production. The effects of fallow (F) periods and bait crops (clubroot‐susceptible canola (B) and perennial ryegrass (R)) on clubroot severity and P. brassicae resting spore populations were evaluated in five sequences: R–B, B–R, R–F, B–F and F–F. Both host and non‐host bait crops reduced clubroot severity in a subsequent crop of a susceptible canola cultivar compared with fallow. Resting spore and P. brassicae DNA concentrations decreased in all treatments, but were lowest for the R–B and B–R bait crop sequences. In addition, two studies were conducted in mini‐plots under field conditions to assess the effect of rotation of susceptible or resistant canola cultivars on clubroot severity and P. brassicae resting spore populations. One study included three crops of susceptible canola compared with a 2‐year break of oat–pea, barley–pea, wheat–wheat or fallow–fallow. The other study assessed three crops of resistant canola, two crops of resistant canola with a 1‐year break, one crop of resistant canola and a 2‐year break, and a 3‐year break with barley followed by a susceptible canola. The rotations that included non‐host crops of barley, pea or oat reduced clubroot severity and resting spore concentrations, and increased yield, compared with continuous cropping of either resistant or susceptible canola. Growing of a susceptible canola cultivar contributed 23–250‐fold greater gall mass compared with resistant cultivars.  相似文献   

15.
Summary Fallow management is a major strategy for weed control and soil fertility restoration in tropical farming systems. From 1995 to 1998, weed infestation was evaluated in plots managed under 0, 1, 2 and 3 year fallow durations of (1) a natural bush fallow dominated by Chromolaena odorata ; (2) a planted Mucuna pruriens fallow; and (3) a modified bush fallow without C. odorata . The study was conducted at the Nigerian Institute for Oil Palm Research (NIFOR), Benin City, Nigeria. The 3 × 4 factorial experiment was set up in a split plot arrangement. The three fallow types were the main plots and the four fallow durations were the subplots. Each year, the subplots were planted to maize ( Zea mays , cv. TZSR-W) as appropriate and harvested 14 weeks after planting for yield comparison. Continuous cropping and the modified natural bush fallow increased weed diversity and biomass. Irrespective of fallow type, weed infestation was more gradual in the first year of cropping after fallow than in subsequent cropping years. Regardless of cropping intensity, C. odorata and M. pruriens fallows promoted broad-leaved weeds, chiefly Ageratum conyzoides , Tridax procumbens and Phyllanthus amarus , whereas the modified bush fallow promoted grasses. Maize grain yield was higher in the C. odorata and M. pruriens fallows than in the modified bush fallow, but the yield difference diminished with cropping intensity.  相似文献   

16.
采用间歇淋洗好气培养法测定了黄土区旱地不同土壤及施氮量下夏季休闲前后土壤氮素矿化累积量,分析了旱地夏休闲期间土壤氮素矿化特性的变化。结果表明:与休闲前相比,休闲后土壤氮素矿化累积量显著降低,长武及杨凌试点土壤分别降低了29.52%及7.15%;长期不施氮肥处理休闲后土壤累积矿化氮量显著降低,而长期施用氮肥处理休闲前后土壤累积矿化氮量间的差异未达显著水平。相关分析表明,休闲前土壤氮素矿化累积量与土壤有机质、全氮含量间有显著正相关关系。采用双组分一级动力学方程拟合的土壤易矿化氮矿化势休闲前后长武及杨凌试点土壤分别降低了85%及66%,可见夏季休闲显著促进了旱地土壤易矿化氮的矿化。  相似文献   

17.
The population dynamics of Monosporascus cannonballus ascospores in the soils of four muskmelon fields located in a marsh area in Castellón province (eastern Spain) was studied for a 3 year period. Two of these fields were cropped to muskmelon with fallow periods between muskmelon cropping, and the others were in fallow and had extensive flooding periods. Muskmelon cultivation resulted in a progressive increase of the number of ascospores in soil, reaching a maximum 7 months after muskmelon planting (2–4 months after plant death), and a subsequent decline during fallow periods between muskmelon crops. During muskmelon cropping, in-bed and between-bed ascospore numbers were compared and, in general, there were no statistical differences between them. In the fields which were in fallow and flooded, the dynamics found was a progressive decline of the population of ascospores. Soilborne inoculum was viable and capable of infecting muskmelon at the end of the 3 year period in all fields, demonstrating that ascospores of M.␣cannonballus are able to survive for this period of time in the absence of muskmelon cultivation and also that this fungus seems to be well adapted to survive in soils which maintain a high water table during the crop or under flooding conditions.  相似文献   

18.
In response to the extensive development of upland rice on the hillsides of the Madagascan highlands, alternative cropping systems based on conservation agriculture have been recommended to halt declining soil fertility and to limit erosion. To assess the efficiency of these cropping systems in limiting rice blast disease and to measure their yield performance, an experiment was set up in 2003 at Andranomanelatra (1640 m a.s.l.) in the Madagascan highlands. The rice crop was planted every second year following oat (Avena sativa) after common bean (Phaseolus vulgaris), with both conventional tillage and no tillage. For each cropping system, two levels of fertilization were used: (i) organic and (ii) organic + mineral fertilization. The level of blast epidemic was measured on two different cultivars over a 5‐year period. Disease severity was significantly lower in the no‐tillage cropping system than in the conventional tillage system. Mineral fertilization increased the level of blast. A significant interaction between cropping system and fertilization indicated that the impact of fertilization differed with the cropping system. When the level of blast was low, yield was higher in the conventional cropping system but as soon as blast level increased, yield was better in the no‐tillage cropping system. Possible interactions between cropping system and blast epidemics are explained and the problem of high performance but risky cropping systems is discussed.  相似文献   

19.
Parietaria debilis is a dominant annual weed in many non‐tillage fallow and undisturbed areas in Argentina. Herbicides control P. debilis inconsistently. A study on the growth of P. debilis, in a fallow in a soyabean–maize rotation including glyphosate‐resistant cultivars and in an undisturbed area without crops or weed control, was conducted in the central soyabean area of Argentina. The biomass dynamics of all species in the community, as well as biomass, density and growth traits of P. debilis were assessed. Biomass of several species including P. debilis and total biomass were greater in undisturbed than in fallow plots in both years of the study. Diversity was greater in undisturbed plots in 2000, but no differences in diversity were observed in 2001. In both treatments, P. debilis emergence began in March and finished in October and density increased from March to May. High mortality occurred in June and July, particularly in undisturbed plots. In the fallow plots, no other tall weed species were present and light interception was higher in spring when fruit production was at its peak. Conversely, in the undisturbed plots, P. debilis was substantially taller and had greater leaf area due to lower light interception by the high canopy of the rest of the community. In fallow, P. debilis is favoured by single applications of glyphosate, because the herbicide eliminates competitors. Control, if applied, should be directed to both fallow and undisturbed environments, as the weed produces considerable numbers of seeds and can invade extensively managed areas.  相似文献   

20.
The growth response to fertilizer under different soil texture (light clayey soil and composite soil consisting of the light clayey soil and sand), and the timing of N fertilization (early summer and fall fertilization) were determined for annual bluegrass (Poa annua L.) and creeping bentgrass (Agrostis palustris Huds., var. Penncross) in glasshouse experiments. At the three‐leaf stage, both plant species were treated with 30, 100, 300, 1,000, 3000 or 10 000 p.p.m. (w/v) of N, P2O5 and K2O equivalent to ammonium sulfate (N), calcium superphosphate (P) and potassium chloride (K). Three weeks after fertilization, the dry weight of shoots or roots was measured. Both plant species were more sensitive to N than to P or K; however, creeping bentgrass required a higher rate of N (1000 p.p.m.) for maximum shoot and root growth than did the weed (300 p.p.m., N). Shoot growth of both plant species was strongly affected by the timing of N fertilization and soil texture; their shoot responses to N increased in the order: composite soil > light clayey soil, and early summer N fertilization > fall N fertilization, and this tendency was especially marked for creeping bentgrass. These results suggest that the response of annual bluegrass to fertilizer is similar to that of creeping bentgrass; however, the two plants are different in regard to the N requirement or their relationship between response to N and application timing and/or soil texture.  相似文献   

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