Building Soils for Better Crops, Third Edition

The Bottom Line: Nutrients and Plant Health, Pests, Profits, and the Environment

SARE Outreach
Fred Magdoff and Harold van Es | 2010 | 294 pages
PDF (6.8 MB)

This title is temporarily out of print. We expect to publish an updated edition in the spring/summer of 2021.

Management practices are all related. The key is to visualize them all as whole-farm management, leading you to the goals of better crop growth and better environmental quality. If a soil has good tilth, no subsurface compaction, good drainage, adequate water, and a good supply of organic matter, plants should be healthy and have large root systems. This enables plants to efficiently take up nutrients and water from the soil and to use those nutrients to produce higher yields.

Figure 18.1 Influence of soil organic matter and its management on nutrient availability.

Doing a good job of managing nutrients on the farm and in individual fields is critical to general plant health and management of plant pests. Too much available N in the early part of the growing season allows small-seeded weeds, with few nutrient reserves, to get well established. This early jump start may then enable them to outcompete crop plants later on. Crops do not grow properly if nutrients aren’t present at the right time of the season in sufficient quantities and in reasonable balance to one another. Plants may be stunted if nutrient levels are low, or they may grow too much foliage and not enough fruit if N is too plentiful relative to other nutrients. Plants that are under nutrient stress or growing abnormally—for example, in the presence of too low or too high N levels— are not able to emit as much of the natural chemicals that signal beneficial insects when insect pests feed on leaves or fruit. Low K levels aggravate stalk rot of corn. On the other hand, pod rot of peanuts is associated with excess K within the fruiting zone of peanuts (the top 2 to 3 inches of soil). Blossom-end rot of tomatoes is related to low calcium levels, often made worse by droughty, or irregular rainfall or irrigation, conditions.

When plants either don’t grow well or are more susceptible to pests, that affects the economic return. Yield and crop quality usually are reduced, lower ing the amount of money received. There also may be added costs to control pests that take advantage of poor nutrient management. In addition, when nutrients are applied beyond plant needs, it’s like throwing money away. And when N and P are lost from the soil by leaching to groundwater or running into surface water, entire communities may suffer from poor water quality.