Influence of Precipitation on Plant Production at Different Topographic Positions in the Nebraska Sandhills

Several studies have evaluated the spatial distribution of cool- and warm-season grasses across different topographic positions in the Nebraska Sandhills, but limited research has explored topographic differences in total plant production or production of plant functional groups in relation to variable amounts of precipitation. This study evaluated how spring and growing season precipitation influenced plant production at four topographic positions common in the eastern Nebraska Sandhills. Plant production data were collected from annually moved grazing exclosures in mid-June (peak cool-season grass production) and mid-August (peak warm-season grass production) during a 17-yr period from 2001 to 2017. Total plant production and precipitation use efficiency were 35 ? 58% greater on interdune positions, and precipitation marginal response for total plant production was more sensitive to increases in spring and growing season precipitation on interdune compared with dune positions in both mid-June and mid-August. The greater precipitation marginal response of total plant production on interdune positions was driven primarily by greater increases in cool-season grass production with increasing spring or growing season precipitation. Warm-season grass precipitation marginal response was not different among the topographic positions, but production was 23 ? 70% greater on interdune compared with dune topographic positions in mid-August. When differences in the amount of each topographic position at the study location were accounted for, growing season precipitation explained 49% of the variation for total plant production in mid-August, but spring precipitation only explained 23% of the variation for total plant production in mid-June. Because of the differential response of plant production at dune and interdune positions, incorporating the relative amount of each topographic position into estimates of plant production at the pasture or ranch scale will provide better information for adjusting stocking rates to more accurately match animal demand with forage availability.     

Long-term storage of blood prior to whole-blood lymphocyte culturing

Studies were conducted to investigate the effect on blastogenesis of long-term storage of blood prior to whole-blood lymphocyte culturing. Peripheral blood from normal cattle was utilized. Blood from each animal was divided into 2 parts, A and B, following collection. Part A was left intact while RPMI-1640 culture medium was added to part B immediately following collection. Both parts were then kept at room temperature for a total of 7 days and a portion of each blood was tested every day. The cultures were incubated and assayed for [³H] thymidine incorporation into their DNA. It was observed that intact blood (A) was good for 4 days but deteriorated thereafter. Addition of RPMI-1640 to B prolonged the keeping quality of blood for 7 days prior to culturing. The possible application of these findings are discussed.     

The Entomophthorales of Israel and their arthropod hosts: Seasonal occurrence

The seasonal occurrence of entomophthoralean host-pathogen combinations and of conidialvs. resting spore production in Israel is presented and discussed. The data recorded during 1968–1979 concern the following species and their recorded hosts:Conidiobolus apiculatus, C. coronatus, C. osmodes, C. thromboides, andConidiobolus spp.;Entomophthora planchoniana;Neozygites fresenii; Erynia erinacea, E. neoaphidis, E. nouryi, E. occidentalis, E. phalloides, E. phytonomi andE. radicans.     

The effect of thiosulfate on phosphorus availability and uptake by plants

A growth chamber experiment was conducted to examine the effect that banding urea or a thiosulfate source with monoammonium phosphate had upon fertilizer phosphorus uptake and dry matter yield of barley and rapeseed. For barley, fertilizer phosphorus uptake and dry matter yield were significantly increased when a thiosulfate source was banded with monoammonium phosphate, but not when urea was banded with monoammonium phosphate. Fertilizer phosphorus uptake and dry matter yield of rapeseed were not significantly affected by banding either a thiosulfate source or urea with monoammonium phosphate.     

In vitro stimulation of bovine peripheral blood lymphocytes: suppression of phytomitogen and specific antigen lymphocyte responses by aflatoxin.

The effects of aflatoxin B1 on responses of the peripheral blood lymphocytes (PBL) of 2 normal animals to phytohemagglutinin, concanavalin-A, and pokeweed mitogen and of the PBL of 2 Mycobacterium bovis-infected animals to phytohemagglutinin and purified protein derivative of M bovis (PPD) were studied. Aflatoxin concentrations of greater than or equal to 10 microgram/ml significantly suppressed the lymphocyte response of normal animals to the phytomitogens. Lymphocyte response of M bovis-infected animals to specific antigen PPD was significantly suppressed at aflatoxin concentration of 0.5 microgram/ml. Fifty- to 100-fold higher concentrations of aflatoxin were required to produce 50% suppression of lymphocyte response to phytomitogens, as compared with that produced to PPD.