Effect of Corn, Sugarbeets, and Fallow on Zinc Availability to Subsequent Crops
Field observations indicated that Zn deficiency of beans (Phaseolus 
vulgaris L.) was sometimes more severe than expected when 
grown on fallowed soil that was low to marginal in available Zn. 
The objectives of this study were to determine the effects of fallow, 
sugarbeets (Beta vulgaris L.), and corn (Zea mays L.) on Zn availability 
to subsequent crops grown on a Portneuf silt loam (Durixerollic 
Calciorthids, coarse silty, mixed, mesic). The sugarbeet and 
corn plant tops and sugarbeet roots were removed, and 11.2 kg Zn 
ha-1 was applied on one-half of each plot before fall plowing 25-cm 
deep. Beans, sweet corn, or potatoes (Solanum tuberosum L.) were 
planted the following spring. Whole plant samples of beans and 
sweet corn and potato stems, leaflets, and petioles were sampled for 
chemical analyses during the growing season. All bean plants were 
Zn deficient when grown after fallow or sugarbeets but not after 
corn or where Zn fertilized. Potatoes and sweet corn did not show 
any Zn deficiency symptoms or any growth responses to Zn fertilization. 
The average zinc concentration in beans (vegetative development 
stage, V3) following Corn was 20.5 mg kg-1 compared with 
12.5 mg kg-1 following fallow or sugarbeets without Zn fertilization. 
The average Zn uptake by beans (V3) following corn was 1.3 g ha-1 
compared with 0.6 g ha-1 after fallow or suprbeets without Zn 
fertilization. The Zn uptake after corn was even greater than where 
11.2 kg Zn ha-1 was applied to fallow or sugarbeets (1.3 vs. 0.9 g 
Zn ha-1). Enhanced Zn availability following corn persisted 
throughout the growing season and into a second bean crop, although 
at a decreased level. Similar trends occurred with potatoes 
and sweet corn. Soil DTPA-extractable Zn was not significantly 
different after fallow, sugarbeets, or corn. These results indicate that 
Zn deficiency in sensitive crops may be alleviated or prevented depending 
upon the preceding crop grown, and that factors not measured 
by DTPA can significantly influence Zn availability.
Potato nutritional management changes and challenges into the next century
Plant nutrients are important components of the intensive production system used for potatoes. Nutrient management practices need to be improved for sustained and increased productivity. Better mangement decisions will be made when accurate information is available about (a) crop residues and rotation effects on nutrient cycling, (b) the nutritional characteristics and requirements of each variety, (c) bioavailability of nutrients in soils, and (d) fertilization and tillage effects on nutrient-use efficiencies. Plant growth and nutrient uptake responses to different nutrient availabilities must also be understood to maximize growth and nutrient efficiencies. Diagnostic management techniques for nutrients need to be related to fundamental chemical and biological processes in the soil and plant system to be applicable to different environments. This information can then be packaged with other knowledge into a comprehensive crop management system. These changes should bring our agronomic practices into better harmony with the natural processes of the production system, and yet be responsive to social and environmental concerns, and economic reality.
The guaianolides of ambrosia cumanensis HBK : The structures of cumambrins A and B☆
Abstract Cumambrins A and B isolated from Ambrosia cumanensis HBK were shown to be guaianolides with structures Ia and Ib.