Large sums of money are spent annually for herbicides to control weeds in fall sown wheat. Many of these weeds are killed by such treatments while others survive and mature seed. Viability of seeds produced by weeds injured by systemic or growth regulator type herbicides has long been a matter of great interest, much speculation, and very little research. Data on this subject are needed in order to intelligently use chemicals for weed control.

Doctor of Philosophy / Department of Agronomy / Phillip W. Stahlman / Saflufenacil is an experimental herbicide for control of broadleaf weeds in various crops including several herbicide resistant weed biotypes. Wheat is highly tolerant to preplant and preemergence applications of saflufenacil, but winter wheat growers prefer to apply herbicides postemergence (POST) in early spring. Objectives of this research were to (1) evaluate winter wheat and four common broadleaf weed species response to POST treatments of saflufenacil applied alone and in combination with bentazon or auxin herbicides at various rates both with and without adjuvants, and to (2) determine the possible mechanism(s) responsible for crop safening observed when saflufenacil is applied with 2,4-D amine or bentazon in winter wheat. Growth chamber, greenhouse, and field studies showed saflufenacil at a minimum rate of 25 g/ha controlled blue mustard and flixweed >85% when saflufenacil was applied alone or mixed with dicamba, 2,4-D amine, 2,4-D ester, or MCPA ester. Also, mixtures of bentazon with 13 g/ha of saflufenacil resulted in death of kochia, but increasingly higher rates of 2,4-D amine were needed to achieve 90% growth reduction when saflufenacil rates were decreased from 50 to 25 to 13 g/ha. In general, most of the saflufenacil combinations tested controlled henbit <85%. Leaf necrosis and stunting of winter wheat were reduced by tank mixing saflufenacil with dicamba, 2,4-D amine, or bentazon, but not with MCPA ester or 2,4-D ester. Including nonionic surfactant (NIS) in mixtures of saflufenacil plus 2,4-D amine resulted in significant wheat injury similar or greater than injury caused by saflufenacil plus NIS. Finally, 2,4-D amine enhanced saflufenacil absorption into winter wheat plants, whereas bentazon reduced absorption of saflufenacil. No more than 11% of applied saflufenacil translocated out of treated leaves to other plant parts when applied alone or when saflufenacil was mixed with 2,4-D amine or bentazon. Metabolism of saflufenacil by wheat plants was not affected by tank mixing with bentazon, but saflufenacil metabolism was slowed by mixing with 2,4-D amine. Overall, these studies indicate saflufenacil can potentially be used POST in wheat at an optimum rate of 25 g/ha plus 2,4-D amine or dicamba to effectively control blue mustard and flixweed.

Doctor of Philosophy / Department of Agronomy / Dorivar Ruiz Diaz / Winter annual weeds (WAW) could affect nitrogen supply for corn production. The objectives of first study were to determine the diversity and abundance of WAW and to evaluate the effect of delaying herbicide applications on nitrogen supply and no-till corn response. Research was conducted in 2010 and 2011 at 14 sites in eastern Kansas. A factorial arrangement of three herbicide application dates (Nov.-Mar., April, and May) and five N rates were used. The three most abundant WAW across sites were henbit, purslane speedwell, and horseweed. Delaying herbicide application until April significantly reduced early corn N uptake by 52 mg N plant-1, chlorophyll meter readings at silking by 3.4%, and grain yield by 0.48 Mg ha-1 across sites. An additional 16 to 17 kg N ha-1 was needed to maintain yield if herbicide application was delayed until April. Starter and foliar micronutrient fertilization can potentially increase corn and soybean yield. The objectives of the second study were to evaluate crop response from combinations of starter and foliar fertilizers that contain N-P-K mixtures with and without a blend of micronutrients at four sites for each crop under irrigated conditions. No early corn growth or yield increase was attributed to application of micronutrients (Fe, Mn, Zn, Cu, and B) beyond what was achieved with N-P-K starter fertilization. There was an increase in soybean height (8 cm) and yield (293 kg ha-1) with starter fertilizer containing N-P-K plus micronutrients over the control. No increase in corn or soybean yield was obtained with foliar fertilization. The objective of the third study was to compare soil mobility and changes in soybean nutrient concentration in the leaf and seed from Mn and Zn sources (EDTA and oxysulfate) at two sites. Zinc sources were more mobile in the soil. Both Zn sources increased seed Zn concentration. Manganese oxysulfate increased seed Mn concentration. However, soybean trifoliolate leaf and seed Mn concentration decreased with soil-applied Na2EDTA and MnEDTA. This response was attributed to formation of FeEDTA and increased Fe supply that reduced root Mn absorption. Manganese EDTA is not recommended for soil application.

Magistrantūros studijų baigiamajame darbe pateikiami piktžolių dygimo dinamikos (trumpaamžių, daugiamečių ir vyraujančių rūšių piktžolių) ir burokėlių derlingumo duomenys tiriant įvairių organinių mulčių ir skirtingo storio sluoksnių liekamąjį poveikį. Darbo objektas – raudonojo burokėlio (Beta vulgaris var. vulgaris) agrofitocenozė. Darbo metodai: piktžolių daigų skaičiavimui kiekviename laukelyje buvo pažymėtos keturios pastovios aikštelės 0,2 x 0,5 m. Apskaita atlikta kas 10 dienų, nuo gegužės 20 d. iki rugsėjo 30 d. Kiekvienos rūšies piktžolių daigai suskaičiuoti ir išrauti. Piktžolių kiekis perskaičiuotas vnt. m-2. Pagal piktžolių biologinį grupavimą išskirtos trumpaamžės ir daugiametės piktžolės. Nustatytos vyraujančios piktžolių rūšys. Burokėlių derlingumas nustatytas svėrimo metodu. Gautas derlius iš laukelio perskaičiuotas į t ha-1 absoliučiai švarių burokėlių derlių. Darbo rezultatai. Gausiausiai piktžolės dygo gegužės trečią – 765,6 vnt. m-2 ir birželio pirmą – 270,6 vnt. m-2 dekadas. Vėliau piktžolių dygimas mažėjo visų variantų laukeliuose. Anksčiau įterpti šiaudų, durpių ir žolės mulčiai nežymiai (4,7-6,7 proc.) skatino piktžolių dygimą per visą tyrimų laikotarpį. Nustatytas nevienodas mulčių liekamasis poveikis trumpaamžių piktžolių dygimui. Įterpti durpių ir žolės mulčiai skatino trumpaamžių piktžolių dygimą nuo 5,2 iki 12,6 proc. Paprastosios rietmenės 20 proc. gausiau rasta ankstesniais metais durpių mulčiu mulčiuotuose laukeliuose, smulkiažiedės galinsogos... [toliau žr. visą tekstą] / Master degree final research paper provides weed germination dynamics (annual, perennial and predominant weeds sorts) and red beet productivity data when researching residual effect of various organic mulches and different thickness layers. Object of the work – red beet (Beta vulgaris var. vulgaris) crop. Method of the work – to compute weed sprouts each field was divided into four permanent sites 0.2 x 0.5 m. These were observed every 10 days from May 20 till August 30. Each weed species sprouts were counted and torn out. Number of weeds was translated into units. m-2. According to biological grouping of weeds annual and perennial were distinguished. Predominant weed species were established. Red beet productivity was determined by weighting. Received yield from the field was translated into t ha-1 totally useful red beet yield. The results of work. Most of the weeds germinated in the 3rd decade of May – 765.6 weeds number m-2 and 1st decade of June – 270.6 weeds number m-2. Later germination of the weeds decreased in the plots of all treatments. Straw, peat and grass mulches, previously incorporated, moderately (4.7 to 6.7 percent) stimulated weed germination during the entire study period. The different residual effect of mulches was determined for germination of annual weeds. The incorporated peat and grass mulches promoted germination of the annual weeds from 5.2 to 12.6 percent. Echinochloa crus - galli were found thicker by 20 percent in the plots that in previous... [to full text]