摘要:

Use of gel polymers has been highly publicized as a means of water conservation. Mixed results have been obtained. A major problem is that the gels do not swell or rehydrate when buried five or more cm deep in soil. They may function only once.

ISSN:0010-3624    

DOI:10.1080/00103629409369016

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

California has just experienced a six‐year drought. Even though the drought is over, it will eventually return; it always does in California. With population up to 32 million, cities do not have enough water, even with normal rainfall. Protection of the environment via legal processes in 1993 is claiming a share of the water. Because agriculture is a big user of water for irrigation in California, it is accused of wasting water and is looked upon as a source of new water for cities. Actually great strides have been made in increasing the efficiency of water use in agriculture in California and elsewhere, and agriculture contributes a 10 percent share of state income and is one of the most stable industries in the state. The theoretical amount of water needed to produce adequate food for the people of California is around 20 million‐acre feet or 24 billion m3. Urban people use four million‐acre feet or five billion m3as does industry. Total farm use for irrigation is 24 million‐acre feet (29 billion m3), down considerably in recent years, but one‐half of farm produce is exported out of the state or nation, and there are some non‐food crops also. Additional transfer of water to cities and for environmental protection of rivers, wetlands and deltas will decrease agricultural production. Successful recycling of urban waste water can add significantly to the total water supply. Water‐soluble polymer soil conditioners can make it easier to irrigate with reclaimed water to help water conservation.

ISSN:0010-3624    

DOI:10.1080/00103629409369017

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Organic growers traditionally have placed synthetically compounded fertilizers onto the list of products which they ban. Generally, synthetically compounded fertilizers are very simple compounds that supply nutrients to plants. They are not even all inorganic if urea is classed as organic. Synthetically compounded fertilizers are identical with similar compounds found in nature. Plants cannot tell the difference. There are, however, at least ten compelling reasons for using natural organics as fertilizers: (a) Recycling for political and economic reasons, (b) Recycling to conserve natural resources, (c) To decrease soil acidification, (d) To decrease soil erosion and compaction by increasing levels of soil organic matter, (e) To protect groundwaters from nitrate buildup, (f) To protect surface waters from algal bloom, (g) To help have a favorable soil biology, (h) To help improve water‐use efficiency, (i) Some synthetically compounded fertilizers are dangerous to produce, and (j) “Organic” certification can result with economic benefits to growers.

ISSN:0010-3624    

DOI:10.1080/00103629409369018

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The new 1993 sludge rule of the EPA (Environmental Protection Agency) sets (a) concentration limits for ten different heavy metals in sludge or sludge products that are sold or given away for use on soil, (b) cumulative loading rates for those ten metals in soil, (c) concentrations of the metals that can be considered as “clean” sludge, and (d) annual loading rates that must be met if the sludge is not “clean” but below the ceiling concentrations. The rule allows for widespread liberal use if the pathogen aspects are complied with. This encourages addition of organic carbon to soils which is urgently needed for soil improvement. The permissible levels of heavy metals may be too high, however, because EPA obviously did not fully consider the interactions which occur when 2–3–4–5 or more heavy metals are at high levels simultaneously especially after 40 years of use when decomposition releases some of the heavy metals. We have observed field situations where use of sludge composts for as many as 40 years have led to heavy metal toxicities particularly for Cu and Zn and with soil pH that is very acid.

ISSN:0010-3624    

DOI:10.1080/00103629409369019

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Regulatory levels of lead are becoming increasingly stringent because of hazards to children. Levels as little as 15 mg dL‐1in the blood stream are associated with chronic disorders in children. Not more than 15 and as little as 5 parts per billion lead are recommended for drinking water. Leaded gasoline, leaded paint and composts have added lead to soil although that from compost is believed to be essentially unavailable to the food chain at least in the short term. Wallace Laboratories’ soil testing on the national basis indicates that some soils are capable of passing lead into the food chain. The State of California recommends that daily intake of lead not exceed 75μg per day for an adult, 20μg per day during pregnancy and 6μg per day for a child. Soil and plant tests for lead in urban situations especially are indicated. In general DTPA‐extractable lead should be less than 20 mg/kg soil and concentrations of lead in plants should be considerably less than 3 mg/kg on the dry weight basis. Some growers have supplied micronutrients in excess to the point of toxicity.

ISSN:0010-3624    

DOI:10.1080/00103629409369020

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Tobacco will wipe out ten percent of the world's population at its present level of use. Cancer of various kinds is the major effect. Over the life span of 70 years, this means that about 100,000 per million will die of tobacco‐induced cancer in the USA. There will be an equal number of cancers for other reasons. Many natural products in food we eat and even the air we breath can induce cancers. Legislation controlling use of pesticides aim at keeping the risk of cancer at less than one in a million over a life span of 70 years. Against a background of 200,000 per million or even half that, one in a million is virtually impossible to detect, even with the best of science. Risk analysis is far from being an exact science. The procedures used to assess risk, even though full of assumptions, are reasonably safe. Most likely they err on the safe side by orders of magnitude. The Delaney Clause, California Proposition 65 which banned all pesticides known to be carcinogenic in California, and failed California Big Green of 1990 all mean well but they detract from a farmer's ability to deal with the more real problems of creating a sustainable agriculture. The present analytical revolution has increased fears of pesticides but it should do the reverse; perceived risk is a bigger problem than real risk.

ISSN:0010-3624    

DOI:10.1080/00103629409369021

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Agricultural, forestry, and related industries will always be in trouble with an endangered species act which protects every species. Nature never did intend for all of its creatures to be permanent. Many species have ceased to exist either when they no longer had a role in an ecosystem function or when the ecosystem upon which they depended no longer could supply their needs. The fittest survive. The task to preserve all species is virtually impossible and very expensive; approach to it should first consider the integrity of an ecosystem. An ecosystem may be important to a species, but that species may not be important to the ecosystem. Economics and potential intrinsic value are valid reasons for protecting species, but good science should dictate all that is done. There is merit in protecting ecosystems more than endangered species; a multidisciplinary, holistic approach is needed. New rules need to be developed regarding endangered species; their roles in ecosystem functions and their ability to successfully compete need to be part of the decision process. Soil as a component of most ecosystems is sometimes an endangered species; it deserves protection. Special problems with the various organisms in soils probably can never be resolved, especially since many, if not most, are not even known.

ISSN:0010-3624    

DOI:10.1080/00103629409369022

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The USA has two very large national debts and they both are a threat to agriculture and soil. Agriculture in the USA very much depends upon federal governmental programs, otherwise food would not be inexpensive. The huge national debt that has accumulated threatens the support system which to a degree helps protect agriculture and the land it uses. The Cooperative Extension Service may disappear in the future to save federal money. Crop subsidy programs tied to soil conservation may be dissolved. Deregulation of agriculture could allow farmers more freedom to improve land but this could occur only if farmers were organized to control supply according to demand. Since farmers may never have this ability, they will remain largely in control of congress which struggles with a $4 plus billion going up national debt. The debt won't easily go away and is compounded by the annual interest charge on it. There are several reasons for the national debt but interest cost perpetuates the problem. There is also an unpaid national environmental debt and much of it involves need for soil improvement.

ISSN:0010-3624    

DOI:10.1080/00103629409369023

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The biggest environmental problem facing the world is probably not population but rather consumerism. If each person on the average in the USA consumes 18 times as much as a person in some developing nations, the effective population of the USA is greater than that of either India or China and both combined. Although the USA is an efficient productive nation, there is good evidence that on the average, citizens of the USA consume more than they produce. This has serious environmental consequences as well as economic. It is important to understand that those who care for the soil eventually interact with those who do everything else in the world.

ISSN:0010-3624    

DOI:10.1080/00103629409369024

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Biotechnology and genetic engineering promise a new explosion of agricultural productivity going into the twenty‐first century. But according to reports from the United Nations and others, the soils of the world are continually being seriously degraded, some beyond repair, and others repairable only at high cost. It is doubtful if a superlative new agriculture can be successfully launched on seriously damaged soil. We must have soils worthy of the coming new agriculture. Success will be directly proportional to the quality of soil. Programs outlined in other papers of this series, if followed, can result in the kind of soil needed. Increasing the soil organic matter, more precision in the use of fertilizers and other inputs, promoting water conservation, correctly using gypsum (calcium) and water‐soluble polymers together with careful conservation of crop residues and other wastes with ideal tillage, and making smart choices of crop rotations, all together can create biologically, physically and chemically quality soil to grow crops that are extremely productive.

ISSN:0010-3624    

DOI:10.1080/00103629409369025

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor