Crop production, potential

It is possible to look at the situation with biomass from a different perspective. The amount of land with crop production potential in 1990 was 2.45 x 1013 m2. In order to support 9 billion people in 2050, 0.416 x 1013 m2 of additional land will be required for crop production. The remaining land available for biomass energy would then be 1.28 x 1013 m2. This would result in a projected total of 7 to 10 TW of power. 

This would be a massive undertaking, requiring that almost all of the crop production potential on the planet be utilized. In addition, there are significant obstacles, not the least of which is the issue of water resources. Also, cellulose derived from biomass must be readily converted to a liquid fuel—preferably ethanol—presenting a challenge for the chemical sciences. 

Despite the use of 2.5 million tons of pesticide worldwide, approximately 35% of potential crop production is lost to pests. An additional 20% is lost to pests that attack the food post-harvest. Thus, nearly one-half of all potential world food supply is lost to pests despite human efforts to prevent this loss. Pesticides, in addition to saving about 10% of world food supply, cause serious environmental and public health problems. These problems include human pesticide poisonings fish and bird kills destruction of beneficial natural enemies pesticide resistance contamination of food and water with pesticide residues and inadvertent destruction of some crops. 

How weeds produce their effect is the subject of continuing research. As rather recently defined, the negative effect of weeds on crop plants includes both competition and allelopathy (1.) and has been termed interference. Previous weed science research considered the competition component foremost and, usually, solely (e.g. 2). Allelopathy, however, has received some attention recently, with a number of symposia and reviews devoted to allelopathic effects. Some of these cover the effects of weeds on crops (3, 4, 5). In this chapter, I review the possible role of allelopathy in weed interference in crop production in the Mid-South. A second objective of this review is to indicate where research is needed and to suggest potential lines of future research, especially with respect to the developing role of conservation tillage practices in this region. 

It was emphasized in the two conference reports (36, 37) that proper understanding and application of allelochemicals could lead to potentially increasing the crop productivity by protecting the crop plants from natural toxins and by increasing the crop yields by the action of natural stimulants. 

Biomass potentials are mainly determined by agricultural productivity and the amount of land accessible for energy crop production. The total area under energy crops in the EU was around 1.6 million hectares in 2004 (estimate for 2005 2.5 million hectares), which represents nearly 3% of the total arable land. AEBIOM (2007) estimated a total biomass supply of 220 MtOE for the year 2020, while 23 MtOE are covered by wood-based bioenergy (direct from forests) and 88 MtOE by agriculture-based energy crops (by-products not considered). The Commission has estimated that about 15% of the EU s arable land (17.5 million hectares) would be used to reach the targets for 2020. 

Seeds, leaf crops, and grasses are very efficient protein producers from the standpoint of amount per unit area. As indicated in Table IV, the more commonly used seeds and legumes, soybeans and wheat have relatively high protein production potentials (around 400 to 800 kg/ hectare). 

The impact of allelopathy on crop production has received increasing attention recently. A number of potentially growth-inhibitory... 

In some studies, retardants have been implicated in yield enhancement mediated by the manipulation of crop canopy structure and the removal of dominance characteristics, leading to a more uniform crop and potentially higher yields. Senescence may be delayed. Although the maintenance of green tissue is a clear advantage with respect to yield production, prolonged seasons can expose the crop to damaging episodes of adverse weather and counteract the potential benefits of PGR treatment. 

Performance and market share for competitive herbicide products Since the USEPA Special Review was initiated in 1994, acres treated with various corn herbicides have been carefully monitored. No clear alternative has proved to be a possible replacement to atrazine. Several facts are noteworthy. No corn herbicide introduced between 1994 and 2000 reached a 10% market share, nor did the market share increase for putative atrazine replacements like 2,4-D or bromoxynil (Table 13.6). These new products suffered from one or more of the following limitations limited spectrum of weeds controlled, crop injury potential, or rotational restrictions. Meanwhile, atrazine s total market share remained constant at approximately 70%. To date market retention has been poor when new herbicides are used alone. Virtually all com herbicides introduced since 1994 are used with atrazine, and the percentage of acreage treated in combination with atrazine is increasing (Table 13.6). 

Sturz, A.V., Christie, B.R., Nowak, J. Bacterial endophytes Potential role in developing sustainable systems of crop production. CritRev Plant Sci 2000 19 1-30. 

In a search for safer biodegradable plant growth substances that may have potential uses in agriculture, particularly for crop production, our laboratory has developed some new bioassay systems to screen various plants for growth-regulating activity. Our screening efforts resulted in the discovery of both growth promoters and inhibitors. 

The world uses about one-half of the land area potentially available for crop production, but most of the additional land lies outside densely populated countries. This could mean that increased food production will come from continuing and strengthening research, development, and extension programs to provide increasing yields. Table 1.3 shows the approximate world food consumption broken down into developing and developed countries. Farmers produce food no matter where they are located. 

Table 11.5 Threshold levels of potentially toxic elements (PTEs) in Water for crop production (modified from Pescod, 1992 and references therein)...

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