Facts and Myths of Feeding the World with Organic Farming Methods - Principles of Sustainable Soil Management in Agroecosystems - page 91

as sufficient N, P, and other nutrients are supplied and pests are controlled. The rea-
son that producers using conventional practices often have higher yields is generally
because they have more options for supplying nutrients and controlling insects and
diseases and can often react more timely. To feed a growing world population that
is also becoming more prosperous resulting in diets that include more meat, dairy
products, and eggs that generally require more grain and other feeds for animals, it is
time to accept and promote various types of crop production. The National Research
Council (2010) states that there are four goals required for a sustainable agricultural
system. These are achieving sufficient productivity, enhancing the natural-resource
base and environment, making farming financially viable, and contributing to the
wellbeing of farmers and their communities. A combinative organic-conventional
system has many advantages. Miao et al. (2010) reviewed a number of long-term
experiments. A large number of agricultural experiments were initiated around the
world beginning in the 1800s. Lawes and Gilbert established the Broadbalk plot in
1843 in Rothamsted, England (Rothamsted Research 2006). In the United States, the
Morrow Plots were established in 1876 on the campus of the University of Illinois,
Urbana; the Sanborn Field plots were started in 1888 on the campus at the University
of Missouri, Columbia; and the Magruder Plot was initiated at Oklahoma State
University in 1892. These plots are still active today, although some of them have
been modified substantially. A number of other stations have also been in existence
for more than 50 years, and several of these are listed by Miao et al. (2010). Miao et
al. (2010) concluded from their review that chemical fertilizer alone is not enough
to improve or maintain soil fertility at high levels, and the soil acidification problem
caused by overapplication of synthetic N fertilizers can be reduced if more N fertil-
izer is applied as nitrate relative to ammonium- or urea-N fertilizers. Organic fertil-
izers can improve soil fertility and soil physical properties and result in high yields.
However, long-term applications of organic fertilizers at high rates can lead to more
nitrate leaching and accumulation of phosphorus. Stewart et al. (2000) discussed
the ratio of N and P in manure compared with that in major crops. They stated that
maize ( Zea mays ) and wheat ( Triticum aestivum ) require approximately five times
as much N as P, and that the ratio of N to P in manure is only about 2.5 to 1. Thus, if
sufficient manure is added to supply N needs, there is often a high accumulation of
P. Even when manure supplied only part of the nutrients in a 15-year study in China
by Zhang et al. (2009), there was a very high buildup of available P in the soil at the
end of the study. Enriched P in the soil may be lost through runoff, or leached in soils
with low P retention or in situations of organic P leaching, leading to water pollution
(Edmeades 2003).
Organic fertilizers, when properly used, can provide adequate soil fertility for
maximum yields. For over 4000 years, Chinese farmers managed to produce modest
crop yields and maintain soil fertility using traditional farming practices, emphasiz-
ing integrated and efficient utilization of different strategies of crop rotation, inter-
cropping, all possible resources of organic manures aiming at the most complete
recycling of nutrients (e.g., animal waste, human excreta, cooking ash, compost,
and dredged canal sediments, etc.), and green manures (Wittwer et al. 1987; Ellis
and Wang 1997; Gao et al. 2006; Yang 2006). A Chinese farming proverb says
“Farming is a joke without manuring.” Many ancient Chinese publications mention