Soil water crop relationship pdf writer

soil water crop relationship pdf writer

THE WATER-SOIL-PLANT. RELATIONSHIP. “Maximizing Avocado Production”. Maximizing Avocado Production. Series. Presented by—. Gary Bender and Mary . Soil-water-plant relations are deliberately combined in a relationship which can be probably dependent upon plant turgor pressure, whose relation to soil moisture stress for different She is engaged in writing articles and research papers. plant root zone for optimum crop yield, the study of the inter relation ship between soil pores, its water-holding capacity and plant water absorption rate is.

The International Food Policy Research Institute IFPRI in noted that cassava is an insurance crop that increases food security because they can be left in the ground until needed [ 7 ]; and their usage as a source of ethanol for fuel, energy in animal feed and starch for industry is increasing. The crop is amenable to agronomic as well as genetic improvement juxtaposed with a high yield potential under good conditions and performs better than other crops under suboptimal conditions.

It is grown widely in several countries in sub-Saharan Africa and Madagascar. Cassava was introduced into Africa in the latter half of the sixteenth century from South America and, perhaps, also from Central America, where it is believed to have originated. Globally, there has been widespread production of cassava across continents. Thailand, Vietnam, Indonesia and Costa Rica have been reported as the world leading exporters of cassava [ 8 ].

It was concluded that cassava production in the tropical Nigeria needs to increase with the rising population and this has been significantly influenced by the changing climate and the poor soil quality conditions arising due to soil degradation [ 8 ]. This invariably laid credence to the pertinence of galvanising strategies for boosting cassava production and export in the tropical Africa.


This review will however consider soil quality, water characteristics and their synergy for suitable and optimum production of cassava in tropical soils. World cassava production in source: Soil quality and cassava production The demand on soil resources in increasing, especially for new and conflicting soil functions like enhancing food security, improving water quality, disposing urban and industrial wastes and mitigating climate change.

Thus, soil quality and its management are more important now than ever before, especially in developing countries that are characterised by high risks of soil degradation, predominantly resource—poor and small landholders [ 4 ]. Soil quality is the capacity of soil to perform specific functions of interest to human. Soil quality has historically been equated with agricultural productivity. Soil conservation practices to maintain soil productivity are as old as agriculture itself. Soil quality is implied in many decisions farmers make about land purchases and management and in the economic value rural assessors place on agricultural land for purposes of taxation.

Furthermore, soil quality is defined as the ability of a soil to perform functions that are essential to people and the environment [ 9 ]. Soil quality is not limited to agricultural soils. The first step in science of agriculture is the recognition of soils and of how to distinguish that which is of good quality and that which is of inferior quality. However, in spite of numerous definitions of soil quality, reviewed reports suggest that the widely accepted definition of the concept of soil quality was laid down by the Soil Science Society of America SSSA in which states that soil quality is the capacity of a specific kind of soil to function within natural or managed ecosystem boundaries, sustain plant and animal productivity, maintain or enhance water and air quality and support human health and habitation.

Soil functions keep changing with time and are different with developing compared with developed countries [ 4 ]. Larson and Pierce [ 10 ] defined soil quality as the capacity of a soil to function within the ecosystem boundaries and interact positively with the environment external to that ecosystem. Three soil functions are considered essential: However, no soil is likely to successfully provide all these functions, some of which occur in natural ecosystems and some of which are the result of human modification.

Hence, soil quality depends on the extent to which soil functions to benefit humans. The qualities of tropical soils are imperative indices towards the sustainable production of cassava. Cassava is known to be a heavy feeder, and literatures have opined that more than average output is obtainable from cassava grown on marginal lands.

However, in view of the ever-increasing population of the tropical Africa most notably in Nigeriaand with the production rates seldom meeting the increasing market demands of the produce, production of cassava on quality soils is therefore an imperative factor which when juxtaposed with good management and adequate climatic conditions, the production of cassava can be improved.

Samson Odedina, while demonstrating the profitability of cassava production enterprise to young people and emerging farmers noted that farmers obtain an average yield of 8—10 tonnes of cassava per hectare, adding that the yield is far below the potentials of the crop.

He further stressed that if the soil conditions are well managed, farmers can get up to 50—60 tonnes per hectare if they follow the recommended soil management practices.

This increasingly justifies the pertinence of the quality of soils used for cassava production in tropical Nigeria. In addition, the FAO in reported that cassava has the reputation of causing serious erosion when grown on sloppy soils [ 11 ]. Researchers have also argued that this reputation is undeserved, since cassava is often grown on already-eroded soils where few other crops can survive and be productive.

Nevertheless, concise reviews of related literatures generally maintained that cassava production on slopes causes increased erosion on an annual basis than other crops grown under the same circumstances. Cassava, in conjunction with common bean Phaseolus vulgarisupland rice and cotton, tends to cause considerably more erosion than cereals like maizepeanut, sugarcane, pineapple or sweet potato. This was predominantly attributed to the fact that cassava needs to be cultivated at a relatively wide spacing.

Contrarily, once the crop canopy is closed, erosion is usually minimal during the remainder of the crop cycle Figure 2. The soil condition used for the production of cassava in Nigeria is of utmost importance if the demands for the produce are to be met before the year Figure 3.

For good growth of cassava, the soil used for production must have adequate room for water and air movement and for root growth. Also, the rising pressure on agricultural lands has made it difficult to obtain high-quality lands for sustainable production of deep-rooted crops like cassava. The insurgence of climate change and its effects on tropical soils has also increased this malady.

These, therefore, lay emphasis on the true need of establishing soil management techniques aimed at boosting soil physical, chemical and biological conditions—which are main indices for soil quality towards the optimum production of cassava in this high-demand region of West Africa.

Hence, based on reviewed statistics, cassava production in Nigeria will increase greatly with optimum soil, environmental and management conditions.

Cassava demand and supply projections in Nigeria [13]. Soil quality assessment for cassava production Soil is likely to show great variability in their physical, chemical and biological properties because the soil is a heterogeneous unit. Knowledge of variability of soil properties is highly indispensable as this can affect crop yield. A study of the variability trends of soils is essential in order to highlight the soil potentials and enhance their management and productivity [ 14 ].

They emphasised that it is important to be aware of the effect of spatial variability of soil properties when choosing indicator variables of soil quality for crop production.

Although when, how and where to collect soil samples for soil quality determination may differ according to the objective of the assessment being made, management history and current inputs should also be considered to ensure valid interpretation of the information. Soil quality assessment for agricultural production is an important operation towards sustainable crop and livestock production in tropical Africa. Owing to the high degree of variability that is characteristic of tropical soils, there is a need for the assessment of soil condition and capability to offer suitable crop outputs.

Fundamentally, soil productivity for cassava production is a function of soil quality and management. Soil quality assessment is the process of measuring the management-induced changes in soil as we attempt to get soil to do what we want it to do. The ultimate purpose of assessing soil quality is to provide the information necessary to protect and improve long-term agricultural productivity, water quality and habitats of all organisms including people [ 16 ]. Basically, Soil Science Society of America [ 3 ] reported that soil quality is an inherent attribute of a soil that is inferred from soil characteristics or indirect observations.

soil water crop relationship pdf writer

The MDS may include biological, physical or chemical soil characteristics otherwise known as soil quality indicators Figure 4. Showing key indicators of soil quality [18]. Furthermore, the US Department of Agriculture [ 19 ] defined soil quality indicators as physical, chemical or biological properties, processes and characteristics that can be measured to monitor changes in the soil.

The types of indicators that are the most useful depend on the function of soil for which soil quality is being evaluated. Sojka and Upchurch [ 20 ] highlighted that while recognising some controversies about the basic concept of soil quality, considerable progress had been made in the s in identifying the indicators of soil quality.

However, indicators of soil quality can be generally categorised into four groups: Visual indicators This may be obtained from observation or photographic interpretation. Exposure of subsoil, change in colour, ephemeral gullies, ponding, run off, plant response, weed species, blowing soil and deposition are only a few examples of potential locally determined indicators.

Visual evidence can be a clear indication that soil quality is threatened or changing [ 21 ]. Adeoye and Agboola [ 22 ] maintained that for sustainable cassava or any other crop production, the presence of spear grass on the field to be cultivated is a good indication of a soil with good fertility conditions.

Physical indicators These are related to the arrangement of solid particles and pores. The soil physical characteristics are necessary part of soil quality assessment for cassava production because they often cannot be easily improved [ 23 ] during the course of the cropping season.

Lal [ 18 ] reported that important soil physical parameters to be assessed include soil aggregation, available water capacity, texture, saturated hydraulic conductivity, bulk density, infiltration rate and rooting depth.

Researchers have further stressed the need for establishing a quantitative assessment of these soil physical parameters in order to predict biomass productivity, soil organic carbon dynamics, transport processes of water and solutes, etc. Chemical indicators Assessment of soil quality based on soil chemistry, whether the property is a contaminant or part of a healthy system requires a sampling protocol, a method of chemical analysis and an understanding of how its chemistry affects biological systems and interacts with mineral forms and standards for soil characterisation and suitability classification for cassava production in tropical soils.

In light of these, Larson and Pierce [ 10 ] laid emphasis on those chemical properties that either inhibit the root growth or affect nutrient supply due to the quantity present or the availability. Nevertheless, Abua [ 26 ] highlighted the importance of maintaining high levels of nitrogen and phosphorus in the soils as chemical indices for quality soils to be used for cassava production in southern Nigeria. Biological indicators Basically, microorganisms and microbial communities are dynamic and diverse, making them sensitive to changes in soil conditions [ 27 ].

Their populations include fungi, bacteria including actinomycetes, protozoa and algae. However, some soil organisms such as nematodes and bacterial and fungal pathogens reduce plant productivity. Visser and Parkinson [ 28 ] reported that diverse soil microbiological criteria may be used to indicate deteriorating or improving soil quality, and measurement of one or more components of the nitrogen cycle including ammonification, nitrification and nitrogen fixation may be used to assess soil fertility and soil quality.

Nevertheless, USDA [ 19 ] devised biological indicators of soil quality to include measurement of micro- and macro-organisms, their activity, or by-products; and also suggested measurement of decomposition rates of plant residue in bags or measurement of weed seed numbers, or pathogen population can also serve as biological indicators of soil quality.

Water is regarded as the most important of the four soil physical factors that affect plant growth mechanical impedance, water, aeration and temperature [ 29 ]. The optimal moisture conditions for any crop vary depending on many factors such as soil type, climate conditions, growth rate and habit, etc. The water movement in soils for any given crop production a case study of cassava is defined by the soil water characteristic curve.

The soil-water characteristics also known as the soil-water retention or desorption curve can be described as a measure of the water holding capacity i. SWCC is an indication of the ability of the soil to release water for plants use. The soil-water characteristics are a conceptual and interpretative tool through which the behaviour of unsaturated soils can be understood.

As the soil moves from the saturated state to drier states unsaturated statesthe distribution of the soil, water and air phases changes as the stress state changes. The relationships between these phases take on different forms and influence the engineering properties of unsaturated soils [ 323334 ]. Generally, the curve is a function of soil texture and soil structure.

The curve also explains how different soil structures will hold and release water. The relationship between pore water suction and water content, as presented in a SWCC, is one fundamental relationship used to describe unsaturated behaviour of a soil. Suction is inversely proportional to the water content in a soil. Suction generally increases as the soil desaturates.

Increasing suction generally results in high resistance to flow and increase in effective stress. Desiccation is a by-product of the increased effective stress [ 36 ]. Increasing suction in compacted clays due to decrease in water content modifies the flow behaviour of covers.

Soil-Water-Crop Relationship: A Case Study of Cassava in the Tropics

During desiccation, the saturation of a liner is reduced and the remaining pore water is held at increasingly large suction. Soil moisture retention curve [35]. The relationship between saturation and suction during desiccation is described using the SWCCs. Knowledge of suction and corresponding water content in the soil can be used to predict cracking potentials of liners. The onset and resulting amount of cracking can be correlated to a soil-specific critical suction level [ 31 ].

Hence, the SWCC provides critical input to the design of a compacted clay cover liner due to its potential impact on flow rates and the desiccation process. Soils with wider ranges of pore sizes exhibit greater changes in matric suction with water content. The SWCCs of compacted clay soils depend on the compaction water content, compactive effort and plasticity index [ 31 ].

Classification of soil water Water occurs in the soil pores in varying proportions. Some of the definitions related to the water held in the soil pores are as follows: A soil sample saturated with water and left to drain the excess out by gravity holds on to a certain amount of water. The volume of water that could easily drain off is termed as the gravitational water Figure 6. This water is not available for plant use as it drains off rapidly from the root zone.

The water content retained in the soil after the gravitational water has drained off from the soil is known as the capillary water.

soil water crop relationship pdf writer

This water is held in the soil by surface tension. Plant roots gradually absorb the capillary water and thus constitute the principle source of water for plant growth. The water that an oven dry sample of soil absorbs when exposed to moist air is termed as hygroscopic water. It is held as a very thin film over the surface of the soil particles and is under tremendous negative gauge pressure. This water is not available to plants. The above definitions of the soil water are based on physical factors.

Some properties of soil water are not directly related to the above significance to plant growth. These are discussed next. Soil-water constants For a particular soil, certain soil-water proportions are defined which dictate whether the water is available or not for plant growth.

These are called the soil-water constants. The soil-water constants refer to the different stages of moisture in the soil as one moves from a wet soil to a dry soil i. These constants are described below: Over exploitation of groundwater, climatic aberration, decline in water table have resulted in shortage of fresh water supplies for agricultural purpose. To overcome the problems associated with water, different management strategies for efficient utilization and conservation of water resources should be emphasized.

Especially the strategies involved include conservation of water, integrated water use, optimum allocation of water and enhancing water use efficiency. And soil-water relations play a vital role in determining their use efficiency Acharya, Soil-water relations are expressed in terms of ability of the soil to retain, release and transmit water within and across the soil system to the atmosphere.

The processes of infiltration, profile water storage, drainage, redistribution and evaporation of water from the soil are governed by its soil-water relations.

The extent of runoff and erosion that erode the capacity of soil are governed by its soil water relations. The root growth and proliferation are directly related to water availability in the soil profile which also influences penetration resistance to the growing roots. Similarly the availability and movements of nutrients, process of salinization and alkalization are directly or indirectly influenced by soil water relations.

Soil-water-plant relations are deliberately combined in a relationship which can be expressed with a terminology called as Soil Plant Atmospheric Continuum SPAC. SPAC is defined as the movement of water from the soil, through the plant and to the atmosphere along an interconnected film of liquid water Lambers et al. Water movement through the SPAC is driven by the passive movement of water generated by an energy gradient. The energy gradient is created by a difference in water potential from high potential in the soil, to a gradually lower potential in the plant and the atmosphere.

Factors affecting Soil-Water-Plant Relationship There are three major factors that affect the soil water plant relations 1. Weather factors Soil Factors: Any soil factor which affects root density or depth can be expected to influence the response of the crop to irrigation. Mechanical impedance, slow water penetration and poor internal drainage, and deficient aeration frequently are responsible for sparse and shallow roots.

Soil structure, texture, and depth determine the total capacity of the soil for storing available water for plant growth. The total available moisture capacity within the root zone and the moisture-release characteristics of the soil are both important factors determining the rate of change in soil moisture tension or stress. Deep-rooted crops on deep soils usually show smaller responses to irrigations than shallower-rooted crops on the same soil. The rate at which water can move to the absorbing root surface may play an important part in water-soil-plant relations.

Several different aspects of plant growth-such as elongation of plant organs, increase in fresh or dry weight, and vegetative versus reproductive development are easily recognized.