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.
Relationship Between Tissue Zinc Levels and Maturity Period of Field Beans
Most bean varieties (Phaseolus vulgaris) are susceptible 
to zinc deficiency and, if grown where 
zinc deficiency occurs, are invariably listed among 
those crops with the greatest need for zinc fertilization 
(1, 2, 3, 4). Bean plants with mild to moderate zinc deficiency 
symptoms early in the growing season may 
recover and produce essentially a normal yield. However, 
as several individuals have observed (1, 2, 3) 
this early-season zinc deficiency invariably results in 
delayed maturity. This is a critical factor in geographical 
areas where beans may be damaged by fall 
rains or early frost. 
The research reported here establishes quantitative 
relationships between the zinc level in bean tissues 
and the number of days required for maturation. The 
results support previous observations of delayed maturity 
when bean plants have inadequate zinc during 
early growth.
Characterization and gene cloning of a maltotriose-forming exo-amylase from Kitasatospora sp. MK-1785
A maltotriose-forming amylase (G3Amy) from Kitasatospora sp. MK-1785 was successfully isolated from a soil sample by inhibiting typical extracellular α-amylases using a proteinaceous α-amylase inhibitor. G3Amy was purified from the MK-1785 culture supernatant and characterized. G3Amy produced maltotriose as the principal product from starch and was categorized as an exo-α-amylase. G3Amy could also transfer maltotriose to phenolic and alcoholic compounds. Therefore, G3Amy can be useful for not only maltotriose manufacture but also maltooligosaccharide-glycoside synthesis. Further, the G3Amy gene was cloned and expressed in Escherichia coli cells. Analysis of its deduced amino acid sequence revealed that G3Amy consisted of an N-terminal GH13 catalytic domain and two C-terminal repeat starch-binding domains belonging to CBM20. It is suggested that natural G3Amy was subjected to proteolysis at N-terminal region of the anterior CBM20 in the C-terminal region. As with natural G3Amy, recombinant G3Amy could produce and transfer maltotriose from starch.