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.
Assessment of the Zn status of chickpea by plant analysis
Chickpea (Cicer arietinum L.) is extensively grown in areas where soils are deficient in zinc (Zn). To determine the response of chickpea to Zn nutrition and to diagnose Zn status in plant tissue, two glasshouse experiments were conducted using Zn-deficient siliceous sandy soil. In Experiment 1, two genotypes of desi chickpea (Dooen and Tyson) were grown at five Zn levels (0, 0.04, 0.2, 1.0 and 5.0 mg kg-1 of soil). After 4 weeks, no difference in growth and no visible symptoms of Zn deficiency were detected. After 6–8 weeks of growth, chlorosis of younger leaves and stipules occured in the Zn0 treatment, with shoot dry weight being only 24% of that recorded at the highest Zn level. Root growth increased from 0.52 g/plant when no Zn was applied to 1.04 g/plant in the treatment with 0.2 mg Zn kg-1 of soil; no response to further increase of Zn fertilization occurred. Zinc concentration in the whole shoot increased significantly with increased in Zn application. The critical Zn concentration in the shoot tissue, associated with 90% of maximum growth, was 20 mg kg-1 for both genotypes at flowering stage.In the second experiment, two genotypes of desi chickpea (Tyson and T-1587) were grown at three Zn levels (0, 0.5 and 2.5 mg kg-1 of soil) under two moisture regimes (field capacity 12% w/w, and water stress 4% w/w). Shoot growth was influenced by both Zn supply and water stress. The effect of water stress was severe in the 0.5 and 2.5 mg Zn treatments where shoot dry matter was reduced 52 and 46%, respectively. T-1587 was less sensitive to Zn deficiency and produced higher shoot dry weight than Tyson in the Zn0 treatment. Zinc concentration in shoots increased from 5 mg kg-1 when no Zn was applied to 40 mg kg-1 at the highest Zn level. The critical Zn concentration in shoots was 21 mg kg-1.The results of the two experiments showed that the critical concentration for Zn did not differ amongst the three cultivars used and was not affected by soil moisture. Similar studies should be undertaken with a wider number of genotypes to discover if a critical concentration of 20–21 mg kg-1 in the shoot can be used to diagose the Zn status of chickpea genotypes.
The determination of boron in soil extracts, plant materials, composts, manures, water and nutrient solutions
Abstract A rapid colorimetric method for the determination of boron in soil extracts, plant materials, composts, manures, water and nutrient solution is proposed. The method is rapid, reliable and carried out in aqueous solution. A marked advantage is that boron can be determined in the same soil extract or plant material digest used for determination of other elements.