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John V. Westra Kevin J. Boyle Gregory A. Porter 《American Journal of Potato Research》1995,72(2):99-117
Using actual potato production data from Aroostook County, Maine, we investigate the possibility of producers increasing net revenues by modifying rotation practices. By examining rotations as a whole, and incorporating yield effects and changes in production costs across rotations, more realistic pictures of net revenues for each rotation develop than if net revenue for each crop within a rotation is considered independently. Our analyses indicate producers can alter their production practices within the range of rotations used locally to increase net revenues. A key finding confirms the synergistic interaction between grains underseeded with a green manure crop and round-white potato varieties, resulting in decreased production costs, greater potato yields, and increased net revenues. 相似文献
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Mike Sun Susan Siemsen William Campbell Pablo Guzman Robert Davidson Jonathan L. Whitworth Terry Bourgoin Jeff Axford Willem Schrage Gary Leever Alan Westra Steve Marquardt Hossien El-Nashaar Jeff McMorran Oscar Gutbrod Tom Wessels Robert Coltman 《American Journal of Potato Research》2004,81(3):227-231
Fourteen United States (U.S.) seed potato certification agencies surveyed all U.S. seed potato growing areas for presence of the potato spindle tuber viroid (PSTVd). The survey included general surveillance, which involved searching for the occurrence of PSTVd in state seed potato certification records from 1990 through 2000, and a field survey, which involved testing selected crops for PSTVd infection by nucleic acid dot blot hybridization during 1999 through 2001. No PSTVd incident was documented in any of the state certification records, nor was PSTVd detected in the field surveys. All U.S. seed-growing areas were determined to be free of PSTVd. It is concluded that PSTVd has been eradicated and freedom from potato spindle tuber viroid has been successfully maintained in all of the seed potato growing areas in the United States. 相似文献
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The resolved isomer of metolachlor, S-metolachlor, was registered in 1997. New formulations based primarily on the S-metolachlor isomer are more active on a gram for gram metolachlor basis than formulations based on a racemic mixture of metolachlor containing a 50:50 ratio of the R and S isomers. The labelled use rates of S-metolachlor-based products were reduced by 35% to give equivalent weed control to metolachlor. However, several companies have recently registered new metolachlor formulations with the same recommended use rates for weed control as S-metolachlor. This research was done to compare the soil behaviour and the biological activity of metolachlor and S-metolachlor in different soils under greenhouse and field conditions. Although K(d) ranged from 1.6 to 6.9 across the five soils, there were no differences in the binding of metolachlor and S-metolachlor to soil or in the rate of soil solution dissipation in a given soil. However, both greenhouse and field studies showed that S-metolachlor was 1.4-3-fold more active than metolachlor against Echinochloa crus-galli (L.) Beauv. in five different soils and that S-metolachlor was more active than metolachlor in three Colorado field locations. When the rates of metolachlor and S-metolachlor were adjusted for S isomer concentrations in the formulations, there were no differences between the formulations in field, greenhouse or bioassay studies. Thus herbicidal activity is due to the S isomers, with the R isomers being largely inactive. 相似文献
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Growth analysis, absorption and translocation studies were conducted to compare a 1-aminomethanamide dihydrogen tetraoxosulfate (GLY-A) formulation of glyphosate with two isopropylamine (GLY-IPA-1, GLY-IPA-2) formulations of glyphosate on velvetleaf. The two isopropylamine formulations differed by the presence of a surfactant in the formulation, GLY-IPA-1 containing surfactant whereas GLY-IPA-2 did not. Four- to six-leaf velvetleaf was treated with GLY-A and GLY-IPA-1 and GLY-IPA-2 (0, 50, 67, 89, 119, 158, 280, 420, 560 and 840 g AE ha(-1)) with and without ammonium sulfate (AMS; 20 g L(-1)). GLY-A and GLY-IPA-2 included a non-ionic surfactant (2.5 mL L(-1)) in the spray solution at all herbicide concentrations. No additional surfactant was added to GLY-IPA-1. The IC50 value for GLY-A was 88 g AE ha(-1) compared with 346 and 376 g AE ha(-1) for GLY-IPA-1 and GLY-IPA-2 respectively in the absence of AMS. When AMS (20 g L(-1)) was added to the spray solution, the estimated IC50 values were 143, 76 and 60 g AE ha(-1) for GLY-IPA-1, GLY-IPA-2 and GLY-A respectively. Absorption of 14C-glyphosate into the third leaf of five- to six-leaf velvetleaf was three- to sixfold greater 72 h after treatment (HAT) when applied as GLY-A compared with GLY-IPA-1 and GLY-IPA-2 respectively in the absence of AMS. AMS (20 g L(-1)) increased absorption of 14C-glyphosate in all glyphosate formulations two- to threefold, but differences among the formulations remained. Approximately three- and sixfold more 14C-glyphosate applied as GLY-A had translocated out of the treated leaf compared with GLY-IPA-1 and GLY-IPA-2 respectively by 72 HAT. Adding AMS (20 g L(-1)) increased translocation of 14C-glyphosate out of the treated leaf approximately 2.5-fold for all three formulations. The increased efficacy of GLY-A versus GLY-IPA-1 and GLY-IPA-2 on velvetleaf is due to the greater rate of absorption and subsequent translocation of glyphosate out of the treated leaf. AMS increased the efficacy of all three formulations by increasing absorption and translocation of glyphosate in the plant. 相似文献
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Heermann D. F. Hoeting J. Thompson S. E. Duke H. R. Westfall D. G. Buchleiter G. W. Westra P. Peairs F. B. Fleming K. 《Precision Agriculture》2002,3(1):47-61
The USDA-Agricultural Research Service and Colorado State University are conducting an interdisciplinary study that focuses on developing a clearer scientific understanding of the causes of yield variability. Two years of data have been collected from two commercial center pivot irrigated fields (72 and 52 ha). Cooperating farmers manage all farming operations for crop production and provide yield maps of the maize grown on the fields. The farmers apply sufficient inputs to minimize risk of yield loss. The important variables for crop production have been sampled at a grid spacing of 76 m for two seasons. A spatial auto-regressive model was fitted to the data to determine the critical factors affecting yield variability. Thirty one layers of data were included in the analysis, and a total of over 140,000 models were examined. Up to five predictors were used in each model. Variability in water application, nitrate nitrogen, organic matter, phosphorus, topology, percent silt and soil electrical conductivity were significant in explaining the yield variability for Field 1. Variability in water application, ammonium, nematodes, percent clay, insects, potassium, soil electrical conductivity, and topology were significant in explaining the yield variability for Field 2. The tentative conclusion is that the potential economic benefit of site specific management is small where the farmer's management tolerance for risk is low. The potential of site specific management is in reducing the cost of inputs and environmental impact, but could increase risk. 相似文献
7.
Talia Nadler‐Hassar Dale L Shaner Scott Nissen Phill Westra Baruch Rubin 《Pest management science》2009,65(7):811-816
BACKGROUND: Herbicide‐resistant crop technology could provide new management strategies for the control of parasitic plants. Three herbicide‐resistant oilseed rape (Brassica napus L.) genotypes were used to examine the response of attached Cuscuta campestris Yuncker to glyphosate, imazamox and glufosinate. Cuscata campestris was allowed to establish on all oilseed rape genotypes before herbicides were applied. RESULTS: Unattached seedlings of C. campestris, C. subinclusa Durand & Hilg. and C. gronovii Willd. were resistant to imazamox and glyphosate and sensitive to glufosinate, indicating that resistance initially discovered in C. campestris is universal to all Cuscuta species. Glufosinate applied to C. campestris attached to glufosinate‐resistant oilseed rape had little impact on the parasite, while imazamox completely inhibited C. campestris growth on the imidazolinone‐resistant host. The growth of C. campestris on glyphosate‐resistant host was initially inhibited by glyphosate, but the parasite recovered and resumed growth within 3–4 weeks. CONCLUSION: The ability of C. campestris to recover was related to the quality of interaction between the host and parasite and to the resistance mechanism of the host. The parasite was less likely to recover when it had low compatibility with the host, indicating that parasite‐resistant crops coupled with herbicide resistance could be highly effective in controlling Cuscuta. Published 2009 by John Wiley & Sons, Ltd. 相似文献
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J. J Hage R. D. Glas H. H. Westra M. A. Maris-Veldhuis J. T. Van Oirschot F. A. M. Rijsewijk 《Veterinary microbiology》1998,60(2-4):87-98
Six heifers were vaccinated intranasally with the live bovine herpesvirus 1 (BHV1) temperature-sensitive (ts) vaccine strain RBL106 within 3 weeks of birth. These calves most likely still had maternal antibodies against BHV1. Thereafter, these heifers were vaccinated several times with an experimental BHV1 glycoprotein-D (gD) subunit vaccine. At the age of 3 years these 6 heifers were seronegative in the BHV1 gB and gE blocking ELISAs, but had neutralizing antibodies against BHV1, probably induced by the vaccinations with the gD subunit vaccine. Five of these 6 heifers excreted BHV1 after treatment with dexamethasone. Restriction enzyme analysis of the genome of the excreted viruses revealed that all 5 isolates had a BHV1.1 genotype and that isolates of 3 heifers were not obviously different from the ts-vaccine strain. The restriction enzyme fragment pattern of the isolate of 1 heifer was clearly different from the pattern of the ts-vaccine strain. It is concluded that cattle can be seronegative against BHV1 gB and gE but can still carry BHV1 in a latent form. This finding strongly suggests that there are completely BHV1 seronegative cattle that are latently infected with BHV1. The impact of this finding on BHV1 eradication programmes is discussed. 相似文献
10.
Agrawal N Frederick MJ Pickering CR Bettegowda C Chang K Li RJ Fakhry C Xie TX Zhang J Wang J Zhang N El-Naggar AK Jasser SA Weinstein JN Treviño L Drummond JA Muzny DM Wu Y Wood LD Hruban RH Westra WH Koch WM Califano JA Gibbs RA Sidransky D Vogelstein B Velculescu VE Papadopoulos N Wheeler DA Kinzler KW Myers JN 《Science (New York, N.Y.)》2011,333(6046):1154-1157
Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide. To explore the genetic origins of this cancer, we used whole-exome sequencing and gene copy number analyses to study 32 primary tumors. Tumors from patients with a history of tobacco use had more mutations than did tumors from patients who did not use tobacco, and tumors that were negative for human papillomavirus (HPV) had more mutations than did HPV-positive tumors. Six of the genes that were mutated in multiple tumors were assessed in up to 88 additional HNSCCs. In addition to previously described mutations in TP53, CDKN2A, PIK3CA, and HRAS, we identified mutations in FBXW7 and NOTCH1. Nearly 40% of the 28 mutations identified in NOTCH1 were predicted to truncate the gene product, suggesting that NOTCH1 may function as a tumor suppressor gene rather than an oncogene in this tumor type. 相似文献