Climatic change and food insecurity

Monday, July-08-2013

Ali Bakhsh is an aged farmer, based in Nushki district, which is about 148 kilometers southeast of Quetta, the capital of Balochistan, the largest but least developed province of Pakistan.

Ali Bakhsh cultivates mostly wheat, cumin, watermelon and melon in his rain-irrigated lands that bring enough income to him to live a normal life with his family, but now he does not seem happy with farming since he is not able to cultivate wheat nor cumin because of extra-ordinary delay in rain and long draught.

Since last more than one decade, Ali Bakhsh says they are observing drastic change in weather conditions that is inflicting their centuries-old farming which is the mainstay of their economy.

“Our arid lands are stretched over thousands of acres and the source of irrigation is rainwater and tube-wells but because of unusual variation in weather and draughts we are unable to grow wheat, cumin, watermelon and other crops,” he says, adding that these crops used to give a boost to their economy but now they could not even grow wheat to fulfill their needs.

Ali Bakhsh recalls that he had witnessed long droughts consisting ten to 15 years but after long draughts the weather would return in its normal form and the rain would fall timely helping them to cultivate wheat, cumin and other crops.

“In past we have experienced enough rains with the beginning of November which is the best timing for cultivation of wheat and cumin in Nushki and its surrounding districts but during past 8 to 10 years we are going through uneven delay in rains,” he explains.

Like Ali Bakhsh there are hundreds of other farmers whom livelihood is linked with rainwater in most of districts of Balochistan which covers 44 per cent of Pakistan in terms of area and over 80 per cent of its population depends directly or indirectly on agriculture and livestock.

The arid lands of Balochistan which are dependent on rainwater produce thousands of tonnes wheat, cumin, watermelon and melon for the scattered population of Balochistan and farmers not only fulfill their own demands from these yields but also export them to other main cities of the country.

But when draught hits the areas, the farmers not only fall in starvation but are also compel to move to urban areas for search of food that makes their life more miserable.

Muhammad Azeem, another Nushki-based former says if there is timely rain on their apparently barren lands they could produce thousands of tons of wheat that would not only be sufficient for over 0.2 million population of Nushki district but it would also fulfill demands of rest of Balochistan population.

There is a serious shortage of power (energy crises) in the country and because of non-availability of electricity the agriculture sector is facing serious complexity particularly in Balochistan where agriculture in 29 out of 33 districts depends on electricity.

“Since 2001 various districts of Balochistan, including that of district Nushki are virtually passing through a long draught, thus no data of wheat and cumin yield of rain- irrigated lands has been taken,” Sanaullah Badini, an official of agriculture department in district Nushki told The Nation, adding that there are 21 per cent cultivated lands in Nushki which depend on rains while 60 per cent are irrigated through tube-wells.

“Nushki and many other districts have been passing through draught like situation for the last several years. The cycle of rain has also changed manifold as it rains heavily in the month of February instead of November and December which is considered the right time for cultivation of wheat and cumin,” he said, adding that due to variation in the cycle of rain the rain-dependent farmers could not cultivate crops and suffer a lot.

He says rainfall and temperature has a significant effect on wheat crop productivity.Deputy Director Environmental Protection Agency and renowned environmentalist, Mehboub Baloch says delay in rainfall is all because of climatic change since a number of gasses, including Corbin dioxide and hydrocarbon were contributing in climatic change. “Climate change is a global issue and we have been observing a change in climate in Pakistan particularly in Balochistan and the heavy thunderstorm in Gwadar in 2011 and heavy floods in Naseerabad and Jaffarabad were its main example,” he added.

He says owing to climatic change the agriculture sector is also being affected because of which food insecurity is existing, however, if available water reservoirs are used properly and modern technology of irrigation is adopted the formers would be able to irrigate their lands and could produce maximum food. “Besides cleaning water channels (Karezats) delay-action dames should be constructed and the wastage of rain water should be protected from being wasted,” he added.

Courtesy The Nation
News Collected by agrinfobank.com

Pakistan farmers grapple with climate change

Saleem Shaikh and Sughra Tunio

Gujar Khan, Pakistan - After five consecutive dry winters, Abdul Qadeer was jubilant at the prospect of a plentiful harvest of wheat after December rains soaked his farmland.

But the 39-year-old farmer’s hopes were destroyed last month by torrential spring rains and a hailstorm that flattened his wheat crop.

Qadeer is one of many farmers suffering the effects of unpredictable weather patterns and variable rainfall, which scientists believe are linked to climate change.

Now Pakistan’s government is trying to introduce crop insurance to save farmers from economic ruin. Qadeer, who farms land in Gujar Khan, approximately 55 km southeast of Islamabad, Pakistan’s capital, vividly recalls the unexpected volley of pebble-sized hailstones that lashed his 15-acre (6-hectare) field for about 15 minutes one day in the last week of March.

“I could clearly hear dull, clunking sounds of the hailstones that slashed through the stalks of the standing wheat crop and knocked (the ears of wheat) to the ground,” Qadeer said.

He had anticipated harvesting a good crop in the second week of April, but the unseasonal storm destroyed his wheat, causing losses of 800,000 Pakistani rupees ($8,000).

Zaman Ali, a farmer in Islamabad’s southern suburb of Chak Shahzad, says 70 percent of the wheat he was growing on 9 acres (3.6 hectares) was destroyed by strong winds and heavy rain.

Farmers are really defenceless when such unwanted torrential rains and hailstorms strike their crops. We are really completely at the mercy of the weather

Muhammad Riaz, farmer,

Ali believes the yield from the remaining wheat will reach only 60 percent of what it should have been, because the rains brought unseasonably low temperatures, preventing the grain from maturing properly. Ali described the weather as unprecedented in his 15 years of experience growing crops.

“Farmers are really defenceless when such unwanted torrential rains and hailstorms strike their crops,” said Muhammad Riaz, who lost crops worth about 1.6 million rupees ($16,000) on his 24-acre (10-hectare) farm in Haripur, 65 km (40 miles) north of Islamabad. “We are really completely at the mercy of the weather.”

Insurance coming soon?

“The solution to such grim situations that are becoming frequent lies in crop insurance,” said Nazar Muhammad Gondal, Pakistan’s former federal minister for food and agriculture. “Farmers can at least recover some of the financial damages, and are able to cultivate next season crops.”

Crop insurance is not currently available in Pakistan, but Iftikhar Ahmed, chairman of the state-owned Pakistan Agriculture Research Council (PARC), said the government is leading negotiations with insurance firms and banks to introduce a national crop insurance programme, similar to those introduced in Sri Lanka, India and Nepal. It is hoped the insurance will be available by mid-November this year.

In Pakistan, wheat is sown in mid-October and harvested in mid-April. Around 16 million acres (6.5 million hectares) are planted with wheat every year, yielding around 25 million tonnes of grain.

“Eight to 10 years ago, the spring season used to come in the first week of March and last for 25 to 30 days. Now, it comes in late March and lasts for only 15 to 20 days,” said farmer Qadeer.

Spring rain is a rare phenomenon in Pakistan, particularly in northern and central areas. The inclement weather lowered the temperature by 20 degrees Celsius to around 9 degrees this year.

“From March to mid-April, the wheat crop needs (temperatures) above 30 degrees Celsius for its healthy growth of stalk and grain, and to avoid pest attacks,” said Qamar-uz-Zaman Chaudhry, the World Meteorological Organisation’s vice president for the Asia region and a former director-general of the Pakistan Meteorological Department (PMD).

According to PARC’s Ahmed, high moisture levels in the air have also led to fungus and insect infestations.

Production drops

Officials at the federal food security and research ministry in Islamabad say they expect wheat production from rain-fed land to be 30 percent lower than normal as a result of the extreme weather.

Ghulam Rasul, chief meteorologist at the PMD, said that although hailstorms can be forecast six to 12 hours in advance, the damage they cause to crops cannot be staved off.

“We had predicted both torrential rains and hailstorms on March 23 and 24 in the upper and central parts of the country, and dust storms and intermittent rains for two to four days in the last week of March in southern and coastal areas,” he said.

“Since these untimely or unseasonal rains and hailstorm came at a time when most of the winter crops such as wheat, mustard, vegetables were near harvest, nothing could be done to save the standing crops,” he explained.

Ibrahim Mughal, chairman of Agri Forum Pakistan, a nongovernmental farmers’ body based in Lahore, said the government has consulted with representatives of farmers’ groups about ways to make a national insurance programme effective.

The views of smallholders are key because their share of cultivation is around 75 percent.

“We have suggested that, without a mass awareness campaign about the benefits of crop insurance and subsidising premiums for small or subsistence farmers...the insurance programme is unlikely to win the hearts of farmers,” said Mughal.

This article first appeared on the Thomson Reuters Foundation news service

Source: Al Jazeera

Climate change: red alert or red herring?

Climate experts have been drawing a doomsday scenario with threats of natural disasters such as droughts, floods, water wars and other calamities that can be blamed on global warming. The hoopla has led agricultural researchers to ponder on impending food shortages, and therefore a laborious research has begun to produce climate-proof crops that can defy extreme heat or cold.

While researchers and experts have realised the need for change in production ways, the gravity of the situation has not sunk in with government departments.

“Recent disasters have, jolted their (officials’) minds but this area needs much more serious efforts particularly in climate proofing rather than just waiting for damages to happen and then take recourse. More political commitment, investment in relevant institutions, robust strategies and effective implementation and follow-up are needed” said Naseer Memon, a climate change expert.

According to Iftikhar Ahmad, chairman of Pakistan Agricultural Research Council (PARC), increased preparedness for climate-related risk management through a multi-disciplinary approach is the need of the hour.

Time is indeed a critical factor. The impact of extreme weather patterns and scarcity of water will be felt on food production, in the next ten years, according to the Intergovernmental Panel on Climate Change (IPCC).

“This includes development of improved crop varieties with resistance to emerging biotic and a-biotic stresses, introduction of new crop species, investment in new irrigation systems, and use of eco-friendly management options (for example, organic agriculture, bio-pesticides, bio-herbicides),” Ahmad of PARC explained.

However, international agricultural economist Dr Zafar Altaf has dismissed the hype surrounding climate change.

“As plants have an inherent ability to fight drought and rain, there is little need to tamper with nature or fight climate change,” he told Dawn.com.

Meanwhile, several Pakistani agricultural experts have been busy searching for methods that could help climate-proof crops. There have been talks of setting up of national seed banks for such varieties that can withstand extreme events and even grow crops that produce more food, have more nutrients and grow on the same amount of land, with less water.

Despite the interest being shown by his compatriots, Altaf was adamant that climate-proofing is a ‘red herring’ by the west.

According to Altaf, the West’s cropping pattern, which he terms ‘meaningless,’ was inherited as a colonial legacy and is being promoted by its own interests.

“Pakistan will not run out of food, so there is no need for climate-proof crops.”

Underlining the need for innovative farming methods, he added, “new ways require imagination and specialists who are multi-disciplinarian; improved marketing of the produce and achieving food security.”

This, however, cannot be achieved without hiccups. “The pace at which climate changes will occur, needs to be at par with the change in mentality in the agriculture sector,” Altaf said.
“There is an urgent need to raise the educational standards drastically.”

In addition, the farmer has to be inducted in that development paradigm shift. “The best option is to make the farmer a party to decision making,” he said.

The same notion was endorsed by PARC chairman Iftikhar Ahmad, who called for improved climate-related decision-making should be at the farms.
“Farmers need to gain a better understanding of the climate factors that affect crop yield in their environment”.

This, he insisted, would allow decision makers to identify possible management options based on climate information or seasonal forecasts. “That will not only enhance the resilience in various cropping systems but also sustain the farm productivity.”

The threat is that if farmers are not taken along, the implication of climate change on crop yields may lead to the risk of hunger, which could be disastrous as Pakistan is already facing acute malnourishment.

According to Pakistan’s National Nutrition Survey 2011, 57 per cent of the country’s total population of 184 million is facing food insecurity.

The finding of the national survey (carried out by the ministry of health’s Nutrition Wing in collaboration with the Aga Khan University) states that among that 57 per cent, half the women and children were found to be malnourished.

Dr Zulfikar Bhutta, the lead investigator of the nutrition report, believes “increased poverty levels, illiteracy, lack of awareness regarding the right kind of food to take, and a government distracted by non-issues” has led to the unacceptable high levels of malnourishment.

“I find it extremely alarming that we will have a generation of unhealthy children who will grow up to be unhealthy adults.”

Health experts, including Bhutta have long been raising awareness regarding Vitamin A, zinc and Vitamin D deficiency.

While climate change does contribute to the malnourishment crisis, it is only one of the known risk factors that may lead to food insecurity.

“In addition to introducing farmer-friendly policies (for example, those related to market availability and stability), timely availability of inputs (seeds, fertilizers, irrigation water) needs to be ensured to minimise the impacts of climate change” Iftikhar Ahmad said.

According to Altaf, input costs can be reduced by using organic fertilisers as opposed to chemical fertiliser, which is 20 times more expensive. “But the West and the vested interests in this country would not allow such a move,” he said.

He reiterated the need to make the locally produced food easily available and affordable.

“Pakistan can make it on its own provided the marketing is made more relevant and fair.”

“At the moment the physical distance between the consumer and the producer is immense.”

When Pakistan and India were partitioned (in 1947), the number agriculture markets in Punjab was 650, which has now come down to 119.

“Consumers are suffering because of policy indifference. The small farmer can become viable if he does have the facility to sell in markets closer home.”

Altaf emphasized that Pakistan’s problems were not with nature but with humans who do not understand the implications of donor-driven policies.

He went on to add that the assistance provided by international donor agencies does not help.

“They have allowed misallocation of resources because they cannot afford failures. They go to the most likely areas where the projects can be a success – the irrigated areas of Sindh and Punjab provinces.”

“As a result, farmers based in marginal areas and fragile areas are excluded from the developmental process. These marginal areas can produce much more from their indigenous sources. It is the absence of relevant policies that is making life risky.”

Source: Dawn.com

Climate Change: One More Problem for Pakistan

By Kieran Cooke, Climate News Network

This article first appeared at Climate News Network.

The Indus river, originating on the Tibetan Plateau and flowing for nearly 2,000 miles through the disputed territory of Jammu and Kashmir and finally down to the province of Sindh and out into the Arabian Sea, is key to life in Pakistan.

The majority of Pakistan’s 190 million people are involved in agriculture: the Indus, fed by glaciers high up in the Hindu Kush-Karakoram Himalaya mountain range, provides water for 90% of the country’s crops. Meanwhile hydro-power facilities based on the Indus generate around 50% of Pakistan’s total electricity.

Join Us on Facebook

 Climate change is now threatening this vital waterway – and the future of millions in Pakistan. In recent weeks it has launched, in collaboration with the United Nations Development Programme (UNDP), its first ever national policy on climate change.

“Pakistan is among the most vulnerable countries facing climate risks”, says Marc-Andre Franche, the UNDP’s Pakistan director. ”Mechanisms need to be devised for greener, more resilient options for growth and sustainable development… the climate change clock is ticking too fast and the time to act is here and now.”

Pakistan’s scientists say that in order for the new policy to be effective a number of steps need to be urgently taken to mitigate the impacts of climate change. These include developing high temperature-tolerant crop strains, comprehensive flood warning systems and more reservoirs on the upper Indus. But there are serious doubts about funding for such schemes.

Ghulam Rasul, chief meteorologist at the Pakistan Meteorological Department, says weather patterns are becoming increasingly erratic. In the 1999 to 2002 period Pakistan was hit by severe droughts as the flow in the Indus and its tributaries fell dramatically. But from 2010 to 2012 a series of unusually intense monsoons caused the Indus to burst its banks, resulting in widespread floods: thousands were killed and millions displaced.

“Pakistan’s climate-sensitive agrarian economy now faces larger risks from variability in monsoon rains, floods and extended droughts”, says Rasul. “I urge the world to assist Pakistan to deal with climate change.”

Economy at risk

According to data gathered from 56 meteorological stations throughout Pakistan, there has been a marked increase in heat waves and rising temperatures in the vast Indus Delta in recent years.

In an article in the Pakistan Journal of Meteorology, Rasul and others say there is a greater incidence of tropical cyclones and of saline intrusion in coastal regions. Already wheat and banana harvests in the Indus Delta are being affected.

Rising temperatures are also causing health problems among the area’s population. In many cases farmers in the region -  among the poorest people in the world – are abandoning their lands and migrating to already overcrowded cities.

If this trend continues it could have devastating consequences for the wider economy. Sindh and the Indus Delta have become one of the world’s premier cotton-producing areas, feeding Pakistan’s economically vital textile industry. Falling cotton production in the region would not only hurt Pakistan: it would also trigger a substantial rise in world cotton prices.

Join Us on Facebook

Meanwhile in the mountainous far north most glaciers are in retreat, though some in the Karakoram range are stable or even – for as yet unknown reasons – expanding. Experts say that while melting glaciers might offset temperature rises and act as a form of insurance against drought in the short term,  the long term prognosis is not good.

David Grey, former senior water advisor at the World Bank and now visiting Professor of Water Policy at Oxford University, says that although there is insufficient data to come to an accurate long term assessment of what will happen to the Indus, there are deep anxieties.

“We all have very nasty fears that the flows of the Indus could be severely, severely affected by glacier melt as a consequence of climate change. Now what does that mean to a population that lives in a desert – without the river, there would be no life? I don’t know the answer to that question”, he says. “But we need to be concerned about that. Deeply, deeply concerned.” 

Source:

Soil Basics

Soils are vital, fragile, finite natural resources that are essential for the sustained production of food and fiber. Soils, however, are subject to degradation and erosion when mismanaged. Between 1950 and 1993, grain area per person worldwide decreased from 0.58 to 0.33 acres (0.23 to 0.13 hectares). As human populations increase, soil resources are used more intensively, with increasing probability that many practices will lead to deterioration of the resource. Competition between agricultural uses and non-agricultural uses of land, such as support of structures, disposal of wastes, and growing plants for recreational and aesthetic purposes will increase.
In ecosystems, soils, water, air, plants, animals and people have interdependent relationships. Soils are dynamic, living systems whose productivity, through management that often includes additions of nutrients, organic materials and water, can be sustained indefinitely. Soils exhibit unique physical and chemical sorptive qualities and dynamics reflective of their inorganic and organic composition. Cycling of carbon, nitrogen and other nutrient elements in nature involves transformations in soils.
Great diversity occurs among soils, sometimes in very small geographical areas, such as building lots in urban areas. The rise and fall of civilizations sometimes has been related to the wise use and misuse of natural resources including soil and water.
Definitions of soil vary, but one view is that the unconsolidated material at the earth's surface becomes soil when biological activity results in a noticeable accumulation of organic matter as revealed by a dark surface color. Soils that form in loose, fine-grained material weathered from the rock immediately below them are called residual soils. More frequently, soils are formed in materials that have been transported away from the source rock. Examples of such materials are alluvial materials, which have been deposited from running water as in flood plains or deltas; lacustrine material which is deposited in lakes; glacial material which has been moved by ice, and aeolian material which has been transported and deposited by wind.
Many of the intensively used soils in the world are formed in transported materials. Their usefulness often is associated with topography, or with physical and chemical properties inherited directly from the transported material.

Soils are porous natural bodies composed of inorganic and organic matter. They form by interaction of the earth's crust with atmospheric and biological influences. They are dynamic bodies having properties that reflect the integrated effects of climate (atmosphere) and biotic activity (microorganisms, insects, worms, burrowing animals, plants, etc.) on the unconsolidated remnants of rock at the earth's surface (parent material). These effects are modified by the topography of the landscape and of course continue to take place with the passage of time. Soils formed in parent materials over decades, centuries, or millennia may be lost due to accelerated erosion over a period of years or a few decades.
The exposed surfaces of soils are a common sight on almost any landscape not dominated by rock. The surface of a soil reveals very little about the depth of the soil or its subsurface characteristics. A vertical cross-sectional view of a soil is called a soil profile. Each of the horizontal layers which can be seen in the vertical section is called a soil horizon. Horizons are formed because of the integrated effects of climate and biosphere change and generally become less pronounced with depth. The depth of soils, usually 0.6 to 1.8m, is determined by the depth to which the mantle material has been altered in a significant way. That part of the three-dimensional soil body in which the effects of climate and biological activity are most pronounced is the soil solum. In succeeding pages the nature and properties of soils, their management, and environmental public policy issues will be discussed. 

The proportions of these components may vary between horizons in a soil or between similar horizons in different soils. The ratio of soil water to soil air depends upon whether the soil is wet or dry. The mineral matter, composed of particles ranging in size from the submicroscopic to gravel or even rocks in some cases, accounts for the bulk of the dry weight of the soil and occupies some 40 to 60% of the soil volume. Organic matter, derived from the waste products and remains of plants and animals, occurs in largest amounts in the surface soil, but even here seldom accounts for more than 10% of the dry weight of the soil. Soils are very porous bodies. Some 40 to 60% of the volume is interparticle space, or pore space. The pores, highly irregular in shape and size but almost all interconnected by passages, contain soil water, soil air, or both of these. The soil water reacts chemically with the soil solids and usually contains dissolved substances and perhaps suspended particles. The soil air approaches equilibrium with atmospheric air through movement of individual gases. Bedrock is the ultimate source of the inorganic component in soils. When rock is exposed at the surface of the earth's crust, it is broken down into smaller and smaller fragments by physical forces. The fragments may be altered or decomposed by chemical reaction of mineral matter with water and air. Hundreds, thousands, or even millions of years may be required for the weathering or physical and chemical alteration of rock to produce the ultimate end products in soils. Once particles reach a sufficiently small size they can be moved by wind, water or ice when exposed at the surface. It is common, therefore, for small particles to be moved from one location to another. A single particle might occur in several different soils over a period of 100,000 years. Eventually, these particles or their decomposition products reach the ocean where they are redeposited as marine sediments. The silicate group of minerals is dominant in soil systems. The terms, clay mineral and layer silicate, are used almost interchangeably. The dominant chemical elements in silicate clays are oxygen, silicon, aluminum and iron. Important constituents in relatively small amounts are potassium, calcium, magnesium and sodium. Other elements occur in very small amounts in silicates. Carbonates, oxides, phosphates and sulfates are other mineral groups that occur commonly in parent materials. Soils are porous and open bodies, yet they retain water. They contain mineral particles of many shapes and sizes and organic material which is colloidal (particles so small they remain suspended in water) in character. The solid particles lie in contact one with the other, but they are seldom packed as closely together as possible. Texture The size distribution of primary mineral particles, called soil texture, has a strong influence on the properties of a soil. Particles larger than 2 mm in diameter are considered inert. Little attention is paid to them unless they are boulders that interfere with manipulation of the surface soil. Particles smaller than 2 mm in diameter are divided into three broad categories based on size. Particles of 2 to 0.05 mm diameter are called sand; those of 0.05 to 0.002 mm diameter are silt; and the <0.002 mm particles are clay. The texture of soils is usually expressed in terms of the percentages of sand, silt, and clay. To avoid quoting exact percentages, 12 textural classes have been defined. Each class, named to identify the size separate or separates having the dominant impact on properties, includes a range in size distribution that is consistent with a rather narrow range in soil behavior. The loam textural class contains soils whose properties are controlled equally by clay, silt and sand separates. Such soils tend to exhibit good balance between large and small pores; thus, movement of water, air and roots is easy and water retention is adequate. Soil texture, a stable and an easily determined soil characteristic, can be estimated by feeling and manipulating a moist sample, or it can be determined accurately by laboratory analysis. Soil horizons are sometimes separated on the basis of differences in texture. Structure Anyone who has ever made a mud ball knows that soil particles have a tendency to stick together. Attempts to make mud balls out of pure sand can be frustrating experiences because sand particles do not cohere (stick together) as do the finer clay particles. The nature of the arrangement of primary particles into naturally formed secondary particles, called aggregates, is soil structure. A sandy soil may be structureless because each sand grain behaves independently of all others. A compacted clay soil may be structureless because the particles are clumped together in huge massive chunks. In between these extremes, there is the granular structure of surface soils and the blocky structure of subsoils. In some cases subsoils may have platy or columnar types of structure. Structure may be further described in terms of the size and stability of aggregates. Structural class is based on aggregate size, while structural grade is based on aggregate strength. Soil horizons can be differentiated on the basis of structural type, class, or grade. What causes aggregates to form and what holds them together? Clay particles cohere to each other and adhere to larger particles under the conditions that prevail in most soils. Wetting and drying, freezing and thawing, root and animal activity, and mechanical agitation are involved in the rearranging of particles in soils--including destruction of some aggregates and the bringing together of particles into new aggregate groupings. Organic materials, especially microbial cells and waste products, act to cement aggregates and thus to increase their strength. On the other hand, aggregates may be destroyed by poor tillage practices, compaction, and depletion of soil organic matter. The structure of a soil, therefore, is not stable in the sense that the texture of a soil is stable. Good structure, particularly in fine textured soils, increases total porosity because large pores occur between aggregates, allowing penetration of roots and movement of water and air. Consistence Consistence is a description of a soil's physical condition at various moisture contents as evidenced by the behavior of the soil to mechanical stress or manipulation. Descriptive adjectives such as hard, loose, friable, firm, plastic, and sticky are used for consistence. Soil consistence is of fundamental importance to the engineer who must move the material or compact it efficiently. The consistence of a soil is determined to a large extent by the texture of the soil, but is related also to other properties such as content of organic matter and type of clay minerals. Color The color of objects, including soils, can be determined by minor components. Generally, moist soils are darker than dry ones and the organic component also makes soils darker. Thus, surface soils tend to be darker than subsoils. Red, yellow and gray hues of subsoils reflect the oxidation and hydration states or iron oxides, which are reflective of predominant aeration and drainage characteristics in subsoil. Red and yellow hues are indicative of good drainage and aeration, critical for activity of aerobic organisms in soils. Mottled zones, splotches of one or more colors in a matrix of different color, often are indicative of a transition between well drained, aerated zones and poorly drained, poorly aerated ones. Gray hues indicate poor aeration. Soil color charts have been developed for the quantitative evaluation of colors.  Major Elements Eight chemical elements comprise the majority of the mineral matter in soils. Of these eight elements, oxygen, a negatively-charged ion (anion) in crystal structures, is the most prevalent on both a weight and volume basis. The next most common elements, all positively-charged ions (cations), in decreasing order are silicon, aluminum, iron, magnesium, calcium, sodium, and potassium. Ions of these elements combine in various ratios to form different minerals. More than eighty other elements also occur in soils and the earth's crust, but in much smaller quantities. Soils are chemically different from the rocks and minerals from which they are formed in that soils contain less of the water soluble weathering products, calcium, magnesium, sodium, and potassium, and more of the relatively insoluble elements such as iron and aluminum. Old, highly weathered soils normally have high concentrations of aluminum and iron oxides. The organic fraction of a soil, although usually representing much less than 10% of the soil mass by weight, has a great influence on soil chemical properties. Soil organic matter is composed chiefly of carbon, hydrogen, oxygen, nitrogen and smaller quantities of sulfur and other elements. The organic fraction serves as a reservoir for the plant essential nutrients, nitrogen, phosphorus, and sulfur, increases soil water holding and cation exchange capacities, and enhances soil aggregation and structure. The most chemically active fraction of soils consists of colloidal clays and organic matter. Colloidal particles are so small (< 0.0002 mm) that they remain suspended in water and exhibit a very large surface area per unit weight. These materials also generally exhibit net negative charge and high adsorptive capacity. Several different silicate clay minerals exist in soils, but all have a layered structure. Montmorillonite, vermiculite, and micaceous clays are examples of 2:1 clays, while kaolinite is a 1:1 clay mineral. Clays having a layer of aluminum oxide (octahedral sheet) sandwiched between two layers of silicon oxide (tetrahedral sheets) are called 2:1 clays. Clays having one tetrahedral sheet bonded to one octahedral sheet are termed 1:1 clays. Cation Exchange Silicate clays and organic matter typically possess net negative charge because of cation substitutions in the crystalline structures of clay and the loss of hydrogen cations from functional groups of organic matter. Positively-charged cations are attracted to these negatively-charged particles, just as opposite poles of magnets attract one another. Cation exchange is the ability of soil clays and organic matter to adsorb and exchange cations with those in soil solution (water in soil pore space). A dynamic equilibrium exists between adsorbed cations and those in soil solution. Cation adsorption is reversible if other cations in soil solution are sufficiently concentrated to displace those attracted to the negative charge on clay and organic matter surfaces. The quantity of cation exchange is measured per unit of soil weight and is termed cation exchange capacity. Organic colloids exhibit much greater cation exchange capacity than silicate clays. Various clays also exhibit different exchange capacities. Thus, cation exchange capacity of soils is dependent upon both organic matter content and content and type of silicate clays. Cation exchange capacity is an important phenomenon for two reasons: exchangeable cations such as calcium, magnesium, and potassium are readily available for plant uptake and cations adsorbed to exchange sites are more resistant to leaching, or downward movement in soils with water. Movement of cations below the rooting depth of plants is associated with weathering of soils. Greater cation exchange capacities help decrease these losses. Pesticides or organics with positively charged functional groups are also attracted to cation exchange sites and may be removed from the soil solution, making them less subject to loss and potential pollution. Calcium (Ca++) is normally the predominant exchangeable cation in soils, even in acid, weathered soils. In highly weathered soils, such as oxisols, aluminum (Al+3) may become the dominant exchangeable cation. The energy of retention of cations on negatively charged exchange sites varies with the particular cation. The order of retention is: aluminum > calcium > magnesium > potassium > sodium > hydrogen. Cations with increasing positive charge and decreasing hydrated size are most tightly held. Calcium ions, for example, can rather easily replace sodium ions from exchange sites. This difference in replaceability is the basis for the application of gypsum (CaSO4) to reclaim sodic soils (those with > 15% of the cation exchange capacity occupied by sodium ions). Sodic soils exhibit poor structural characteristics and low infiltration of water. The cations of calcium, magnesium, potassium, and sodium produce an alkaline reaction in water and are termed bases or basic cations. Aluminum and hydrogen ions produce acidity in water and are called acidic cations. The percentage of the cation exchange capacity occupied by basic cations is called percent base saturation. The greater the percent base saturation, the higher the soil pH. Soil pH Soil pH is probably the most commonly measured soil chemical property and is also one of the more informative. Like the temperature of the human body, soil pH implies certain characteristics that might be associated with a soil. Since pH (the negative log of the hydrogen ion activity in solution) is an inverse, or negative, function, soil pH decreases as hydrogen ion, or acidity, increases in soil solution. Soil pH increases as acidity decreases. A soil pH of 7 is considered neutral. Soil pH values greater than 7 signify alkaline conditions, whereas those with values less than 7 indicate acidic conditions. Soil pH typically ranges from 4 to 8.5, but can be as low as 2 in materials associated with pyrite oxidation and acid mine drainage. In comparison, the pH of a typical cola soft drink is about 3. Soil pH has a profound influence on plant growth. Soil pH affects the quantity, activity, and types of microorganisms in soils which in turn influence decomposition of crop residues, manures, sludges and other organics. It also affects other nutrient transformations and the solubility, or plant availability, of many plant essential nutrients. Phosphorus, for example, is most available in slightly acid to slightly alkaline soils, while all essential micronutrients, except molybdenum, become more available with decreasing pH. Aluminum, manganese, and even iron can become sufficiently soluble at pH < 5.5 to become toxic to plants. Bacteria which are important mediators of numerous nutrient transformation mechanisms in soils generally tend to be most active in slightly acid to alkaline conditions.  Soils, like other naturally occurring things, come in great variety and exhibit great ranges of properties. Using measurable and observable properties, such as the kind and arrangement of soil horizons, soils can be characterized and named. The soil series is the lowest category within soil taxonomy (classification system). All soils within a single series have uniform differentiating characteristics and arrangement of horizons. This does not mean that all soils within a series are identical; it does mean that they have the same horizonation, but the horizons may be of different thickness, color, structure, etc. within prescribed limits. Some 15,000 soil series have been described and named in the United States. Most series names are taken from the name of a town, city, county, river or other constructed or natural feature near the location where the soil is first described and named. All of the soils within a series will have developed in the same kind of parent material with comparable drainage characteristics and will be of similar age. The effects of climate and biological activity will have been very similar. Consequently, the soils within a series exhibit like properties and respond in like fashion to usage or manipulation. Higher levels of classification are the family, subgroup, great group, suborder and order. All these categories are given generic names which convey as much information as possible about the soil series to be classified within the group. Eleven soil orders form the highest level of classification. Soils classified within each order show only small differences in the kinds and relative strengths of processes that tend to develop soil horizons. Considerable effort by soil scientists has been expended, and continues to be expended, in surveying soil resources. These surveys, when done in a detailed manner, require a soil scientist to traverse the landscape at frequent intervals, stopping periodically to auger or dig into the soil. The soil surveyor plots the occurrence of soils on a map which is subsequently formalized and eventually published in a soil survey report which includes not only the soil maps for a given area, usually a county, but all types of information about the county as well as descriptions of the properties of the soils in the area, their present and potential uses, and potential problems associated with the utilization of the soils for both agricultural and engineering purposes. Such reports are very expensive in terms of labor and money, but they contain information that is of great value to those who utilize soils for any purpose. Unfortunately, many who could use the information in soil survey reports to great advantage do not know that the reports are available. With increased emphasis on planning, which includes land use, on county, state and regional bases, more utilization of soil survey information is being made and even more detailed and more modern soil surveys are being urgently requested in many areas. Much of this information is being digitized for electronic transmission.