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Soil and the extractants used. Critical levels of available Zn 089 mgkg-1 in soil and concentration of Zn in cotton 4 th leaf at 30 DAS and at maturity in leaf were found to be 575 and 246 mgkg -1 respectively.
The critical concentration of Zn in these soils was established at 075 mg kg-1 for rice and that of 280 mg kg-1 in the plant tissue.
Critical limit of zinc in soil. On the basis of 078 ppm Zn as the critical limit it may be inferred that all the soils testing below the threshold value responded to Zn application with the yield response being more than 10 8. The critical Zn concentration in soil and plant below which plant response to Zn application to the soil may be expected was 078 and 19 ppm respectively. In all the soils testing below 078 ppm Zn plants responded to Zn application and the per cent mean response at 5 and 10 ppm added Zn levels was 10121 and 11138 respectively.
The critical limit of Zn in rice soils below which plant response to Zn fertilization may be expected was found to be 21 ppm HCl-extractable Zn. In soils with values below this level the plants showed typical symptoms of Zn deficiency and the percent mean grain straw husk and total dry matter yield g per pot respectively. The critical limit of Zn in these soils was established at 078 mg kg-1 for rice and critical limit of 75 days old rice plants is 245 mg kg-1 below which response to Zn fertilization may be.
The use of various sufficiency levels of yield resulted in a wide range of critical limits. From the results of the present study an appropriate critical limit of deficiency range of 21-374 mg Zn kg -1 for soil and 270-538 mg Zn kg -1 for leaf can be fixed for getting maximum ginger yield in an Ustic Humitropept. The critical concentration of Zn in these soils was established at 075 mg kg-1 for rice and that of 280 mg kg-1 in the plant tissue.
Soil containing Zn below the critical limit responded appreciably to Zn fertilization. A negative response to Zn application was also observed at its higher level. Impact of soil properties on critical concentrations of cadmium lead copper zinc and mercury in soil and soil solution in view of ecotoxicological effects Rev Environ Contam Toxicol.
A pot culture experiment was conducted to determine the critical limit of Zn for rice grown in Veeranam command area Vertisol and Entisol. The soil contained CaCO3 - 033-754 pH- 62-88 EC- 027-16 dSm -1 and organic carbon 27-114 g kg -1. The results for boundary of between soil deficient and sufficient classes or critical levels by plant response column order procedure and interaction chi-square model for Fe Mn Zn Cu and B critical values were determined as 47 112 07 14 and 05 mg kg -1 soil respectively.
Predictable values for critical levels of micronutrients were also calculated as 995 94 87 88 and 78 respectively. A response to zinc is possible when the soil DTPA Zn soil test is 075 or less and is likely when the DTPA zinc soil test is 05 ppm or less. Current research does not support the widespread use of chelated zinc applied in-furrow for corn production.
Critical levels of available Zn 089 mgkg-1 in soil and concentration of Zn in cotton 4 th leaf at 30 DAS and at maturity in leaf were found to be 575 and 246 mgkg -1 respectively. Soil compaction can also reduce zinc availability. Soil pH Soil acidity pH influences the availability of zinc more than any other factor with lower zinc solubility as the pH increases.
Therefore zinc deficiency usually is limited to soils with a pH above 65. Overliming of soils especially sands may induce zinc deficiency. Soil Phosphorus High levels of phosphorus may.
Under the experimental conditions the available soil P would have to be as low as 0704 mg kg 1 to achieve the target grain Zn concentration of 40 mg kg 1 and at this level the grain yield would only be 4127252 kg ha 1. Soil and the extractants used. Critical limits of micronutrients identified in a particular soil type may not be applicable in other soil types.
For instance critical limit for Zn had been established as 060 mg kg-1 soil in almost all the states except in Gujarat 050 mg kg-1 soil and Tamil Nadu 120 mg kg-1 soil. Similarly critical limit for Fe varies. Zinc in common with the other micronutrients can affect growth when its content is either lower or above a critical level due to deficiency andor toxicity problems respectively.
The lower critical content of whole plant is 15 mg Znkg in rice and 1522 mg Znkg in maize and 22 mg Znkg groundnut. For the whole young plant values reported include 8 mg Znkg for sorghum and 25 mg Znkg in winter. Background Levels of Zinc in Soil Below is a map of the United States Figure 3 showing the broad range of zinc concentration.
Over 95 of all sampled soils fall within a range of 10 micrograms of zinc per gram of soil to 200 μgg and average 70 μgg7 However more important than the measured amount of.