Importance of Soil and Plant Tissue Analysis, Biology tutorial

Plant Tissue Analysis - Nutrient Concentration:

Nutrient concentration of necessary elements in plant is associated to plant growth or crop yield. Range of tissue concentrations at which supply of the nutrient is adequate for optimal growth is termed sufficiency range. At the upper end of the sufficiency range, plants may be regarded to be participating in luxury consumption, as the extra nutrient uptake hasn't produced extra plant growth. At concentrations above the sufficiency range, plant growth may reduce as nutrient elements reach concentrations which are toxic to plant cells or hinder with the use of other nutrients. If tissue concentrations are in critical range, the supply is just marginal and growth is expected to reduce if the nutrient becomes any less available, although visible foliar symptoms may not be shown. Likewise, plants with tissue concentration lower than smaller value provided in the sufficiency range for the particular nutrient are probable to respond to additions of that nutrient if no other factor is more limiting.

Tissue Analysis:

This comprises of sampling of the tissues, analyzing them for their chemical constituents and interpreting results. Rationale behind tissue analysis is that concentration or contents of nutrients with the specified plant part reflects the nutritional status at that plant of its skill to obtain nutrients from ambient soil and therefore, its growth potential on the site. Measurements are intended to give the direct measure of the nutrients that plant derives from the soil rather than the measure of the nutrients in the soil itself. In plant tissue analysis, certain precautions should be taken, for instance:

  • The correct plant part should be sampled
  • The plant part should be sampled at specified stage of growth, as the considerably as the plant matures
  • It should be recognized that the concentration of one nutrient may be affected by that of another nutrient, because of uncertainties and complexities in interpreting tissue concentration data, plants should be sampled from best and worst areas in the field. Difference between samples may give expensive clues concerning then nature of nutrient problem.

Plant-Stalk Nitrate:

Nitrate content of mature plant stalk is estimated at the end of season, to enhance future nitrogen management of crops. Test is useful in identifying excessive levels of nitrogen in plant at harvest time that in turn, is the indication of excessive levels in soil at the end of the season. High levels of nitrate in plants alert farmers to decrease their nitrogen applications to avoid excess nitrogen leaching in future years.

Significance of soil and plant tissue analysis content:

Application of Plant Analysis:

Plant analysis is very efficient in documenting response to nutrient applications. For instance, leaf concentration has been correlated with yield and soil test values calibration work using plant analysis, crop need have been well established. Nutrient uptake patterns, accumulation and partition have been defined for several crops. Similarly, fertilizer efficiency has been efficiently studied.

i) Problem Solving:

Comparative samples for good and bad areas of production field are very efficient in pinpointing limiting elements. Matching soil samples from the roots zones of plant in each of these areas gives extra evidence of the problem and assists to find out best corrective measure.

ii) Monitoring:

Plant analysis has become essential part of managing healthy crops to improve yield and quality while also maximizing efficiency and protecting environment. Also, plant analysis have provided a means for monitoring waste products on farm lands to make sure maximum crop performance while avoiding pollution of environment with interest in precision agriculture and prescription fertilizer application, monitoring will become even more significant in future.

Application of Soil Analysis:

The only way to find out whether the soil is acidic, neutral or alkaline is by performing the soil analysis. Thus, soil analysis is carried cent for the reasons:

  • To give the index of nutrient availability or supply in the given soil. Soil analysis is designed to estimate the portion of the nutrients from same pool used by body
  • To forecast the probability of obtaining the profitable response to fertilizer application to given crop
  • To estimate fertility status of the soil and plan the nutrient management program.

Plant, Soil and Water Relationship:

Soil Water Content - Potential:

There is a relationship between water potential of the given soil and amount of water held at the field. For instance, as fineness of texture increases, there is general increase in available moisture storage growing on sandy soils is more prone to drought than are those growing on the silt loan in same area.

Similarly, influence of organic matter descries attention as, the available water holding capacity of the well - drained mineral soil having 5% organic matter is usually higher than that of the comparable soil with 3% organic matter. This is, organic matter indirectly affects amount of water available to plants through the influence on soil structures and total pore space. Also, organic matter assists stabilize soil structure and it increases total volume and the size of the pores. This results in the increase in water infiltration and water - holding capacity of soil. Thus, identifying the advantageous effect of organic matter on plant available water is necessary for wise soil management.

Soil Compaction Effects on Matrix Potential, Aeration and Root Growth

Soil compaction usually decreases the amount of water which plants can take up. Four factors account for this negative effect:

  • First, compaction crushes several macrospores and large microspores in smaller pores and bulk density increases, restricting root penetration.
  • Second, compaction reduces total pore space that usually means that less water is retained at filed capacity.
  • Third, reduction in macropore size and numbers usually means less air pore space when soil is near field capacity.
  • Fourth, creation of more very fine micropores will increase permanent wilting coefficient (moisture content of soil at which plants wilt and fail to recover the turgidity) and so decrease available water content.

Therefore, plant - available water is that which is not held very tightly for roots to take up and yet is not held so loosely that it freely drains away by gravity.

Soil Aeration:

Soils are very wet for normal root growth when so much of soil pore air. At this water content, lack of oxygen for respiration restricts root growth. Though, in a compacted soil with very few large pores, oxygen supply may become limiting at lower water contents and potentials as some of the smaller pores will be required for air.

Root Growth in Dry Soil:

Least limiting water range concept tells us that soils are very dry for normal root growth when soil strength (estimated as pressure needed to push the pointed rod through soil exceeds approx 2000 kpa. That is root growth is restricted by lack of oxygen at the wet end of range and by the inability of roots to physically push through soil at the dry end.

Osmotic Potential:

For soils high in salts, total moisture stress comprises osmotic potential of the soil solution and the matric potential. Osmotic potential tends to decrease available moisture in such soils at permanent willing coefficient than would be the case because of matric potential alone.

In humid region soils, these osmotic potential effects are in significant, but they become of considerable significance for certain soils in dry regions that may gather soluble salts through irrigation or natural processes.

Soil Depth and Layering:

Total volume of available water will depend on total volume of soil explored by plant roots. This volume may be governed by total depth of soil above root-restricting layers, or by rooting depth characteristic of the particular plant species. Depth of soil available for root exploration is of particular importance for deep - rooted plants, particularly in sub humid to arid regions.

Similarly, soil stratification or layering can influence available water and its movement in soil. Impervious layers drastically slow down the rate of water movement and also limit penetration of plant roots, thus reducing the soil depth from which moisture is drawn. In addition, capacity of soils to store available water determines to the great extent their value for plant growth. For example, forest productivity is frequently related to soil water holding capacity. This capacity gives the buffer between the unfavorable climate and plant production.

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