共查询到20条相似文献,搜索用时 23 毫秒
1.
Paula M. Leddy Timothy D. Paine Thomas S. Bellows Jr. 《Entomologia Experimentalis et Applicata》1993,68(1):43-50
The relationship between ovipositional preference ofSiphoninus phillyreae (Haliday) (Homoptera: Aleyrodidae) and host plant suitability on seven host plant species (Citrus sinensis (L.) cv. ‘Washington’ [navel orange],Fraxinus uhdei (Wenz.) [shamel ash],Heteromeles arbutifolia Roemer [toyon],Malus domestica Mill. cv. ‘Granny Smith’, [apple],Pistacia vera L. cv. ‘Kerman’ [pistachio],Prunus persica (L.) cv. ‘O’Henry’ [peach], andPyrus communis L. cv. ‘Bartlett’ [pear]) was evaluated. Ovipositional preference ofS. phillyreae was determined by measuring egg density after adult female whitefies were given a simultaneous choice of all host plants
for oviposition. Immature survival, developmental time, and adult size were examined to determine host plant suitability forS. phillyreae. All studies were performed under greenhouse conditions.S. phillyreae showed distinct ovipositional preference among host plant species. Host plant species had a significant effect on immature
survival, but little or no effect on developmental time or forewing length. For four of the seven host plant species tested,
there was an association between ovipositional preference and survival. 相似文献
2.
A greenhouse experiment was conducted to determine the influence of cropping variables on nitrogen dynamics in a soil amended
with green manure. Surface soil from various long-term spring wheat rotations was amended with15N-labelled legume green manure (Lathyrus tingitanus) and subsequently cropped (canola [Brassica napus] and spring wheat [Triticum aestivum]) or incubated without a crop for 56 days in a greenhouse. Nitrogen mineralization from both the indigenous soil N and from
green manure was suppressed in cropped soil. Net N mineralization in the uncropped and cropped treatments averaged 73 and
43 mg kg−1, respectively. This difference was attributed, in part, to enhanced biological immobilization in the rhizosphere. Previous
cropping practices also had significant effect on N mineralization, largely by their influence on indigenous organic matter
quality. These observations suggest that short-term N mineralization is favored by fallowing soil after green manure application
whereas N retention in organic matter is favored by immediate cropping.
Contribution 3878873 相似文献
3.
Leal F Loureiro J Rodriguez E Pais MS Santos C Pinto-Carnide O 《Plant cell reports》2006,25(9):978-985
Flow cytometry was employed to determine the ploidy level of Vitis vinifera L. somatic embryo-derived plants obtained from anther culture. Only one among the 41 analysed plants (2.4%) presented somaclonal variation (tetraploidy); the other plants were diploid. No significant differences (P≤0.05) were detected between diploid and parental field plants. No haploid or aneuploid plants were observed. The nuclear DNA content of nine V. vinifera cultivars was also estimated using flow cytometry. A non-significant variation was found among the cultivars, with DNA content ranging from 1.17 pg/2C (cv. ‘Tinta Barroca’ and ‘Viosinho’) to 1.26 pg/2C (cv. ‘Cabernet Sauvignon’). These results and previous studies on other Vitis species suggest that Vitis genome is stable with regard to nuclear DNA content. 相似文献
4.
Patrick H. Brown Steven A. Weinbaum Geno A. Picchioni 《Trees - Structure and Function》1995,9(3):158-164
The influence of alternate bearing on nutrient utilization and total tree nutrient content was investigated in mature pistachio
(Pistacia vera L. cv Kerman trees). Removal of N, P and Zn in fruit and abscised leaves of cropping (‘on’) trees averaged 5, 6, and 2 times,
respectively, the removal in abscised leaflets of the non-fruiting, ‘off’ year trees. One hundred and thirty-five kg N, 131
kg K, 86 kg Ca, 39 kg Mg and 18 kg P per hectare were removed in fruits and abscised leaves in ‘on’ year trees. Tree nutrient
contents and, presumably, the size of nutrient storage pools in dormant trees varied between ‘on’ and ‘off’ years. There was
22% and 14% more N and P, respectively, in dormant trees following ‘off’ than ‘on’ years. The greater N and P accumulation
in ‘off’ year trees is depleted in support of the large fruit demand for N and P during ‘on’ years. In contrast to N and P,
there was greater K and Ca accumulation in perennial tree parts during ‘on’ years than during ‘off’ years. The greater K accumulation
in perennial tree parts and approximately 30% greater removal of K in annual organs during ‘on’ than ‘off’ years suggests
that K uptake could be 4 times higher in ‘on’ year trees than in (non-cropping), ‘off’ year trees. 相似文献
5.
Summary A two-year field study was undertaken using15N isotope techniques to differentiate between stimulation of N uptake and N2 fixation in Western Canadian cultivars of spring wheat (Triticum aestivum L. emend Thell) and durum (T. turgidum L. emend Bowden) in response to inoculation with N2-fixing bacteria.
Bacterial inoculation either had no effect or lowered the % N derived from the fertilizer and the fertilizer use efficiency.
Despite the depression of fertilizer uptake, inoculants did not alter the relative uptake from soil and fertilizer-N pools
indicating that bacterial inoculation did not alter rooting patterns. Nitrogen-15 isotope dilution indicated that N2 fixation did occur.
In 1984, % plant N derived from the atmosphere (% Ndfa) due to inoculation with Bacillus C-11-25 averaged 23.9% while that
withAzospirillum brasilense ATCC 29729 (Cd) averaged 15.5%. In 1985, higher soil N levels reduced these values by approximately one-half. Cultivar x
inoculant interactions, while significant, were not consistent across years. However, these interactions did not affect cultivars
‘Cadet’ and ‘Rescue’. In agreement with previous results, ‘Cadet’ performed well with all inoculants in both years while ‘Rescue’
performed poorly.
Among 1984 treatments, the N increament in inoculated plants was positively correlated with % Ndfa but no such correlation
existed in 1985. N2 fixation averaged over all cultivars and strains was 17.9 and 6.7 kg N fixed ha−1 in 1984 and 1985, respectively. Highest rates of N2 fixation were estimated at 52.4 kg N ha−1 for ‘Cadet’ in 1984 and 31.3 kg N ha−1 for ‘Owens’ in 1985, both inoculated with Bacillus C-11-25, an isolate from southern Alberta soils. Inoculation with either
ofAzospirillum brasilense strain Cd (ATCC29729) or 245 did not result in as consistent or as high N2 fixation, suggesting that these wheats had not evolved genetic compatability with this exogenous microorganism. These agronomically
significant amounts of N2 fixation occurred under optimally controlled experimental conditions in the field. It is yet to be determined if N2 fixation would occur in response to bacterial inoculation under dryland conditions commonly occurring in Western Canada.
Contribution from Agriculture Canada Research Station, Lethbridge, Alberta, Canada. 相似文献
6.
Enhanced nitrogen mineralization in mowed or glyphosate treated cover crops compared to direct incorporation 总被引:1,自引:0,他引:1
Information on how management by mowing and herbicide alter residue quality and nitrogen (N) inputs would be valuable to improve prediction of N availability. Mowing and glyphosate application are widely used by growers to limit cover crop growth and facilitate incorporation. A mixture of cover crops, hairy vetch (Vicia villosa L.), oriental mustard (Brassica junceaL.) and cereal rye (Secale cerealeL.), was investigated as a means to improve soil quality and optimize N availability. There is limited information on how mowing or glyphosate application influence cover crop decomposition and N mineralization from these heterogeneous residues. A rye cover crop was grown in the field over the winter and transferred to containers as an intact soil profile to conduct a greenhouse study. Management treatments (mowing and glyphosate) were imposed eight days before incorporation. Plant and soil N dynamics were monitored. The experiment was repeated with the addition of a tri-mixture cover crop. Inorganic NO3– in bare soil ranged from 6 to 10 g N g soil–1 over 39 days. Similar or lower levels of soil NO3– were observed after rye residue incorporation, from 2 to 6 g N g–1; consistent with N-immobilization. Application of untreated, mixed cover crop residues generally was associated with higher levels of soil inorganic NO3–, from 3 to 11 g N g–1. For both rye and mixed residues, management by mowing or glyphosate enhanced N mineralization by 10 to 100%, compared to untreated residues. At the same time, application of mowing or glyphosate 8 days before cover crop incorporation seemed to reduce the amount of residues by about half compared to untreated controls. Belowground biomass was reduced more than aboveground, although recovery of senescent roots may have been incomplete. Management by glyphosate or mowing enhanced soil inorganic N availability in the short-term while simultaneously reducing carbon and N inputs. 相似文献
7.
Simulating the effects of N availability, straw particle size and location in soil on C and N mineralization 总被引:2,自引:0,他引:2
Predicting the C and N mineralization of straw added to soil is important for forecasting subsequent soil N availability during
and between crop growth cycles. The decomposition module of the STICS model, parameterized under optimal conditions, was used
to predict straw decomposition in sub-optimal conditions, i.e. when contact between soil and residue was poor (due to large
size residues or surface placement) or when mineral N availability was restricted. The data used in the simulations were obtained
from published studies of effects of residue size, location and N availability on C and N mineralization from straw under
controlled laboratory conditions. We selected studies in which the dynamics of C and N mineralization were measured simultaneously.
The dynamics of straw mineralization could be well predicted by the model under optimal conditions with standard parameter
values as derived from measured C/N ratios of the residues, but not under sub-optimal conditions which required a new parameterization. A good fit could be obtained
on these treatments by a marked reduction in the rate constants of residue and microbial biomass decomposition and a marked
increase in the microbial biomass C/N ratio. Our results show the need to include in decomposition models routines for simulating effects of spatial heterogeneity
of residue distribution, different particle sizes and limiting N availability. 相似文献
8.
In situ 15N-labelling was used to provide a quantitative assessment of the total contribution of lupin (Lupinus angustifolius) to below-ground (BG) N accumulation during a growing season under field conditions, and to directly trace the fate of the
lupin BG N in the next season, including quantifying the N benefit from lupin to a following wheat (Triticum aestivum) crop. The experiments were conducted at two sites, both experiencing a semi-arid Mediterranean-type climate in the wheat-growing
region of Western Australia but with differing soil types, a deep sand (Moora) and a sand-over-clay shallow duplex soil (East
Beverley, EB). Lupin shoot and root dry matter and total plant N accumulation, proportional dependence on nitrogen fixation
and grain yield were greater at the deep sand site than the duplex soil site, although there was a similar proportion of shoot
N to estimated total BG N at both sites. The proportion of total plant BG N decreased from the vegetative stage (42–51%) to
peak biomass (25–39%) and maturity (23–34%). From 56–67% of BG N on the deep sand and 74–86% on the duplex soil was not recovered
in coarse roots (>2 mm) or as soluble N, but was present in the insoluble organic N fraction. There was evidence for cycling
of lupin root-derived N into soil microbial biomass and soluble organic N during lupin growth (by the late vegetative stage),
but no evidence for leaching of legume derived BG N during the lupin season. Estimates of fixed N input BG were at least four
times greater if based on total lupin BG N rather than on N recovered in coarse roots (>2 mm). There were no apparent losses
of lupin BG N during the summer fallow period subsequent to lupin harvest at either site. Also, immediately prior to sowing
of wheat there were similar proportions of lupin BG N in the inorganic (20–25%) and microbial biomass (6–9%) pools at both
sites, with the majority of BG N detected in the <2 mm fraction of the soil column. However, the proportion of residual lupin
BG N estimated to benefit the aboveground wheat biomass was relatively low, 10% on the deep sand and only 3% on the shallow
duplex. Some (14%) residual lupin BG N was leached as nitrate to 1 m on the deep sand compared to 8% of residual lupin BG
N leached to the clay layer (0.3 m) on the shallow duplex. About 27% of the residual lupin BG N on the deep sand at Moora
had apparently mineralised by the end of the succeeding wheat season (i.e. recovered either in the wheat shoots, as inorganic
N in the soil profile or as leached nitrate) compared to only 12% at EB. There was an unaccounted for large loss of residual
lupin BG N (50%) from the duplex soil at EB during the wheat season, postulated to be chiefly via denitrification. At both
sites after the wheat season a substantial proportion (32–55%) of legume derived BG N was still present as residual insoluble
organic N, considered to be an important contribution to structural and nutritional long-term sustainability of these soils. 相似文献
9.
Pieter Pypers Liesbeth Van Loon Jan Diels Robert Abaidoo Erik Smolders Roel Merckx 《Plant and Soil》2006,283(1-2):251-264
There are several indications that legumes are capable of accessing sparingly soluble phosphorus (P) in the soil through root-induced
processes. We hypothesize that this plant-induced mobilization of P can be demonstrated if the plant accessible P assessed
by isotopic dilution (‘L-value’) exceeds the corresponding values assessed in soil extracts (‘E-values’). A greenhouse experiment was set up to assess if L/E ratios are affected by P supply and by crop type. The L- and E-values were determined in three P-deficient soils of the Nigerian Northern Guinea savanna (NGS), applied with various rates
of TSP, for two cowpea varieties (Vigna unguiculata L., cv Dan-Ila and cv IT-82D-716) and maize (Zea mays L., cv oba super I) as a reference. Plants grown in control soils were severely P-deficient. Plant growth and shoot P uptake
significantly increased with increasing P application in all three soils and for all crops, but relative yield and shoot-P
responses to P application were similar between maize and cowpea. Both L- and E-values increased with increasing P application. Average L/E ratios for maize were 1.4±0.3 and were unaffected by the P application.
For cowpea in contrast, L/E ratios were 3.1±0.2 (significantly larger than one) in one of the three control soils and significantly
decreased to 1.3±0.1 at largest P supply. Elevated L/E ratios in cowpea were not associated with an increase in P uptake compared
to the other two control soils in which no increase in L/E ratio was observed. It is concluded that cowpea is able to access
non-labile P under P-deficient conditions. However, this process cannot overcome P deficiency in these soils, probably because
P uptake is limited by the small P concentration in the soil solution (1–2 μg P L−1) and this limitation is not overcome by an increase in the accessible soil P quantity (L-value). 相似文献
10.
Erik Steen Jensen 《Plant and Soil》1996,182(1):13-23
Field experiments were carried out on a temperate soil to determine the decline rate, the stabilization in soil organic matter and the plant uptake of N from 15N-labelled crop residues. The fate of N from field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.) residues was followed in unplanted and planted plots and related to their chemical composition. In the top 10 cm of unplanted plots, inorganic N was immobilized after barley residue incorporation, whereas the inorganic N pool was increased during the initial 30 days after incorporation (DAI) of pea residues. Initial net mineralization of N was highly correlated to the concentrations of soluble C and N and the lignin: N ratio of residues. The contribution of residue-derived N to the inorganic N pool was at its maximum 30 DAI (10–55%) and declined to on average 5% after 3 years of decomposition.Residual organic labelled N in the top 10 cm soil declined rapidly during the initial 86 DAI for all residue types. Leaching of soluble organic materials may have contributed to this decline. At 216 DAI 72, 59 and 45% of the barley, mature pea and green pea residue N, respectively, were present in organic N-forms in the topsoil. During the 1–3 year period, residual organic labelled N from different residues declined at similar rates, mean decay constant: 0.18 yr-1. After 3 years, 45% of the barley and on average 32% of the pea residue N were present as soil organic N. The proportion of residue N remaining in the soil after 3 years of decomposition was most strongly correlated with the total and soluble N concentrations in the residue. The ratio (% inorganic N derived from residues): (% organic N derived from residues) was used as a measure of the rate residue N stabilization. From initial values of 3–7 the ratios declined to on average 1.9 and 1.6 after 2 and 3 yrs, respectively, indicating that a major part of the residue N was stabilized after 2 years of decomposition. Even though the largest proportion of residue N stabilized after 3 years was found for barley, the largest amount of residue N stabilized was found with incorporation of pea residues, since much more N was incorporated with these residues.In planted plots and after one year of decomposition, 7% of the pea and 5% of the barley residue N were recovered in perennial ryegrass (Lolium perenne L.) shoots. After 2 years the cumulative recovery of residue N in ryegrass shoots and roots was 14% for pea and 15% for barley residue N. The total uptake of non-labelled soil N after 2 years of growth was similar in the two residue treatments, but the amount of soil N taken up in each growth period varied between the treatments, apparently because the soil N immobilized during initial decomposition of residues was remineralized later in the barley than in the pea residue treatment. Balances were established for the amounts of barley and mature pea residue N remaining in the 0–10 cm soil layer and taken up in ryegrass after 2 years of decomposition. About 24% of the barley and 35% of the pea residue N were unaccounted for. Since these apparent losses are comparable to almost twice the amounts of pea and barley residue N taken up by the perennial ryegrass crop, there seems to be a potential for improved crop residue management in order to conserve nutrients in the soil-plant system. 相似文献
11.
Summary A laboratory incubation experiment followed by a greenhouse experiment was made in a silty clay loam at Pantnagar, India, to recycle plant utilizable N from crop residues such as maize stubble, soybean hay andmoong straw. The beneficial effect of recycled N was tested by a wheat crop. Soybean hay yielded the most NO3–N upon mineralization and also gave the highest wheat grain yield. Maize stubble mineralized the least NO3–N and gave the lowest grain yield.Moong straw occupied an intermediate position. An intervening period of 30–45 days would be required for the residues in question to release plant utilizable NO3–N in sufficient quantities. From a practical view point, soybean hay appears to be an ideal choice of a residue capable of providing sufficient supplemental N for a succeding wheat crop and can be easily fitted into the prevalent cropping sequence. 相似文献
12.
Experiments were conducted to quantify parasitism of Colorado potato beetle,Leptinotarsa decemlineata (Say), by the egg parasitoid,Edovum puttleri Grissell, on 3 different cultivars of eggplant,Solanum melongena L. Levels of parasitism were higher (P<0.05) on ‘Black Pride’ than on other cultivars. The percentage of egg masses that
were parasitized was 1.2-fold higher (P<0.05) on ‘Black Pride’ than on ‘Harris Special’ and ‘White’. The number of eggs per
mass that were parasitized was 1.3- and 1.4- fold greater (P<0.05) on ‘Black Pride’ than on ‘Harris Special’ and ‘White’,
respectively. The percentage of eggs that were parasitized per mass and percentage of emerged adult parasitoids did not differ
(P>0.05) among cultivars; between 2.1- to 2.6- fold more females than males emerged from eggs on all cultivars during the
growing season.Edovum puttleri suppressed the 2nd generation ofL. decemlineata on ‘Black Pride’ and ‘Harris Special’, but did not suppress populations on ‘White’.
相似文献
13.
J. G. Roddick G. Melchers 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,70(6):655-660
Summary Analyses of leaves and ‘tubers’ from somatic hybrids of potato and tomato (‘pomato’ with plastids of potato, ‘topato’ with
plastids of tomato) produced by fusion of protoplasts from liquid cultures of dihaploid potato and mesophyll of tomato revealed
the presence of the two major potato glycoalkaloids (α-solanine and α-chaconine) as well as the tomato glycoalkaloid (αtomatine). The total alkaloid content of leaves was greater than that of ‘tubers’ and similar to levels in the foliage of
parent plants. However, glycoalkaloids were more abundant in hybrid ‘tubers’ than in normal potato tubers by a factor of 5–15.
In hybrid foliage, approximately 98% of the alkaloid present was of potato origin whereas in ‘tubers’ the reverse was the
case, with tomatine comprising 60–70% of the total alkaloid. The similarities in alkaloid content and ratios between the pomato
and the topato lines indicate that plastomes do not influence the biosynthesis and distribution of these alkaloids. The results
indicate that major secondary metabolites may prove useful for assessing the hybrid nature of such plants. 相似文献
14.
H. Barker 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(8):1258-1262
Extreme resistance to the potato V potyvirus (PVV) was found in four potato cultivars that contain Ry genes from Solanum stoloniferum. When plants of these cultivars, were inoculated by grafting in shoot tips from PVV-infected tomato plants, necrotic symptoms
developed in some cultivars, although a full hypersensitive reaction was not elicited, while other cultivars were symptomless.
PVV replication was not detected in any of the inoculated plants by ELISA, an infectivity assay of leaf extracts by manual
inoculation to Nicotiana benthamiana indicator plants, or by ‘return grafting’ of shoot tips taken from newly developed shoots of the potato plants to virus-free
indicator plants of tomato. These methods readily detected PVV infection in inoculated plants of cv ‘Flourball’, which does
not contain an Ry gene and is susceptible, and in cvs ‘Maris Piper’ and ‘Dr Macintosh’, which contain gene Nv conditioning a hypersensitive reaction to inoculation. One of the Ry-containing cultivars, ‘Barbara’, has been previously shown to contain two genes that control extreme resistance, defined
as no viral replication in intact plants, to the potyviruses potato viruses Y and A (PVY and PVA). These genes are: Ry
sto
, which conditions resistance to PVY and PVA, and gene Ra, which conditions resistance to PVA only. It was found that in genotypes from a progeny of the cross ‘Barbara’ (Ry
sto
/Ra)בFlourball’ (ry/ra), extreme resistance to PVV segregated with gene Ry
sto
. It is proposed that either gene Ry
sto
conditions broad-spectrum extreme resistance to the distinct potyviruses PVY, PVA, and PVV or that Ry
sto
represents a family of genetically closely linked genes each controlling resistance to a specific virus.
Received: 27 December 1996 / Accepted: 9 June 1997 相似文献
15.
Foliage litter quality and annual net N mineralization: comparison across North American forest sites 总被引:24,自引:0,他引:24
The feedback between plant litterfall and nutrient cycling processes plays a major role in the regulation of nutrient availability
and net primary production in terrestrial ecosystems. While several studies have examined site-specific feedbacks between
litter chemistry and nitrogen (N) availability, little is known about the interaction between climate, litter chemistry, and
N availability across different ecosystems. We assembled data from several studies spanning a wide range of vegetation, soils,
and climatic regimes to examine the relationship between aboveground litter chemistry and annual net N mineralization. Net
N mineralization declined strongly and non-linearly as the litter lignin:N ratio increased in forest ecosystems (r
2 = 0.74, P < 0.01). Net N mineralization decreased linearly as litter lignin concentration increased, but the relationship was significant
(r
2 = 0.63, P < 0.01) only for tree species. Litterfall quantity, N concentration, and N content correlated poorly with net N mineralization
across this range of sites (r
2 < 0.03, P = 0.17–0.26). The relationship between the litter lignin:N ratio and net N mineralization from forest floor and mineral soil
was similar. The litter lignin:N ratio explained more of the variation in net N mineralization than climatic factors over
a wide range of forest age classes, suggesting that litter quality (lignin:N ratio) may exert more than a proximal control
over net N mineralization by influencing soil organic matter quality throughout the soil profile independent of climate.
Received: 16 December 1996 / Accepted: 8 February 1997 相似文献
16.
Legumes as ground cover are regularly planted to increase nitrogen economy of crops and to improve soil. In the present study
various clover species were evaluated as vegetative ground cover in nursery field production of micropropagated red birch
(Betula pubescensEhrh. f. rubraUlvinen f. nova) in two 2-year experiments. The clover species and cultivars, Trifolium pratenseL. ‘Bjursele’, T. repens L. ‘Jogeva’, T. repens L. ‘Sonja’, T. hybridum L. ‘Frida’, T. incarnatum L. ‘Opolska’, T. resupinatum L. and T. subterraneum L. were compared to grass sod Festuca rubra L. ‘Ensylva’ and to a coverless ground (control). The last one was kept weed free by hand hoeing. Birch (leaves, stems, branches
and roots) and soil nutrient concentrations (N, P, K, Ca, Mg and Fe) were analysed and nutrient ratios in birch determined.
The annual clovers, T. incarnatumL., T. resupinatumL. and T. subterraneumL., provided about the same nutrient status in birch as did the control. Perennial clovers and grass were strong competitors
with trees. High levels of P and Mg in birch leaves relative to N concentration were typical for poorly growing seedlings.
Neither annual nor perennial clovers did generally improve soil nutrient status.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
17.
Source of the soybean N credit in maize production 总被引:2,自引:0,他引:2
Nitrogen response trials throughout the United States Corn Belt show that economic optimum rates of N fertilization are usually less for maize (Zea mays L.) following soybean (Glycine max L.) than for maize following maize; however, the cause of this rotation effect is not fully understood. The objective of this study was to investigate the source of the apparent N contribution from soybean to maize (soybean N credit) by comparing soil N mineralization rates in field plots of unfertilized maize that had either nodulated soybean, non-nodulated soybean, or maize as the previous crop. Crop yields, plant N accumulation, soil inorganic N, and net soil mineralization were measured. Both grain yield (6.3 vs. 2.8 Mg ha–1) and above-ground N accumulation (97 vs. 71 kg ha–1) were greatly increased when maize followed nodulated soybean compared with maize following maize. A partial benefit to yield and N accumulation was also observed for maize following non-nodulated soybean. Cumulative net soil N mineralization following nodulated soybean, non-nodulated soybean, and maize was 112, 92 and 79 kg N ha–1, respectively. Net mineralization of soil N appeared to be influenced by both quality (C:N ratio) and quantity of residue from the previous crop. In addition to an increase in plant available N from mineralization, the amount of soil inorganic N (especially in soil 5 cm from the row) was greater following nodulated soybean than non-nodulated soybean or maize. Based on these data, the soybean N credit appears to result from a combination of a decrease in net soil mineralization in continuous maize production and an increase in residual soil N from symbiotic fixation. 相似文献
18.
S. Promsakha Na. Sakonnakhon B. Toomsan G. Cadisch E. M. Baggs P. Vityakon V. Limpinuntana S. Jogloy A. Patanothai 《Plant and Soil》2005,272(1-2):183-199
It is generally thought that grain legume residues make a substantial net N contribution to soil fertility in crop rotation systems. However, most studies focus on effects of residues on crops immediately sown after the legume crop while in fact in many tropical countries with a prolonged dry season there is a large gap before planting the next crop with potential for nutrient losses. Thus the objectives of this study were* to improve the efficiency of groundnut (Arachis hypogaea L.) stover-N (100 kg N ha –1) recycling by evaluating the effect of dry season stover management, i.e. surface application and immediate incorporation after the legume crop or storage of residues until next cropping in the rainy season. N dynamics (litterbags, mineral N, microbial biomass N, N 2O emissions) were monitored and 15N labelled residues were applied to assess the fate of residue N in the plant–soil (0–100 cm) system during two subsequent maize crops. Recycling groundnut stover improved yield of the subsequent maize (Zea mays L.) crop compared to treatment without stover. A higher N recycling efficiency was observed when residues were incorporated (i.e. 55% total 15N recovery after second maize crop) than when surface applied (43% recovery) at the beginning of the dry season. This was despite the faster nitrogen release of incorporated residues, which led to more mineral N movement to lower soil layers. It appears that a proportion of groundnut stover N released during the dry season was effectively captured by the natural weed population (54–70 kg N ha –1) and subsequently recycled particularly in the incorporation treatment. Despite the presence of weeds major leaching losses occurred during the onset of the rainy season while N 2O emissions were relatively small. There was a good correlation between soil microbial biomass N and first crop maize yield. Incorporation of groundnut residues led to small increases in economic yield, i.e., 3120 versus 3528 kg ha –1 over two cropping cycles in the surface versus incorporation treatments respectively, with corresponding residue 15N uptakes of 4 and 8%, while 15N recovery in water stable aggregates (9–15%) was not significantly different. In contrast, when stover was removed and applied before the first crop, yield benefits were highest with cumulative maize yields of 4350 kg ha –1 and residue utilization of 12%. However, N recycling efficiency was not higher than in the early incorporation treatment due to an asynchrony of N release and maize N demand during the first crop. 相似文献
19.
Elma M. J. Salentijn Andy Pereira Gerco C. Angenent C. Gerard van der Linden Frans Krens Marinus J. M. Smulders Ben Vosman 《Molecular breeding : new strategies in plant improvement》2007,20(1):1-13
Plant genomic research now faces the ultimate challenge to develop applications in crop plants which implies the translation
of gene functions from a model to a crop which is the field of ‘Plant translational genomics’. In this paper we discuss the
perspectives of the candidate gene approach (CGA) as a tool for translational genomics in the ‘whole genome’ era. Factors
to be considered for a successful application of the CGA in crops such as the type of crop, the complexity of the trait and
the type of genes involved are discussed. Several crop traits that require improvement such as tolerance to stress, pod shatter
in Brassicaceae and Fusarium resistance, are evaluated with regard to the potential of a CGA as a tool for crop improvement 相似文献
20.
Large areas of short-rotation eucalypt plantations are being established in south-western Australia on land previously used for agriculture. Options for maintaining soil N supply include retention of harvest residues and legume inter-cropping. We evaluated the effects of adding the residues of five legume species and Eucalyptus globulusleaves on inorganic N dynamics in two soils (a Rhodic Ferralsol or red earth and a Haplic Podzol or grey sand) using two modes of residue application in a laboratory incubation experiment (519 days). The time course of net N immobilisation and mineralisation in both soils was strongly influenced by the type and mode of application. Eucalypt leaves caused strong N immobilisation (–7 mg N g–1 residue-C) over the entire 519-day incubation, whereas for the legume species, N that was eventually immobilised at the start of the incubation, remineralised later to different degrees. Amongst the legumes, largest amounts of N were released from lupin residues (18 mg N g–1 residue-C) and lowest amounts from field pea (2 mg N g–1 residue-C). However, initial residue quality parameters were not significantly (P > 0.05) correlated with N release from the residues. Grinding and incorporating of the residues caused a much greater immobilisation of N than when residues were cut and surface applied. When ground residues were incorporated, immobilisation of N was more severe and endured for longer in the finer textured red earth than in the coarse textured grey sand. Where residues were surface applied, N dynamics were similar for both soil types. The results of this study suggest that legumes used as a mulch in eucalypt plantations are a readily available source of N for trees, and that the benefits from retention of harvest residues are more likely in maintaining soil N fertility on the long-term. 相似文献