Water Agriculture and You

 

Paul Hepperly, Rita Seidel, Christine Zeigler, and John Haberern

 

Abstract

 

Using The Rodale Institute® unique long term experimentation, The Farming Systems (FST) and Compost Utilization (CUT) Trials, we evaluated how regenerative/organic farming systems and practices influences water quality. Lysimeters, devices which collect water that passes through the crop root zone, were used to measure agricultural water outputs which affect surface and ground waters. Nitrate leaching was found in all organic and conventional systems and practices but higher nitrate pulses were associated with soluble synthetic fertilizer and raw manure than with compost applications. Although all fertilization strategies, i.e. synthetic fertilizer, raw manure, and compost, optimized corn yield, only compost reduced nitrate leaching over half compared to both fertilizer and manure applications. Corn herbicides atrazine and metalachlor readily leached past the root systems in conventional corn and soybean production but not in organic systems. Atrazine leaching consistently exceeded the 0.1ppb. This concentration is proven to disrupt male amphibian sexual development. Occasionally atrazine concentration exceeded 3 ppb,  the EPA limit for atrazine in drinking water. Regenerative/organic systems and practices increased the level of soil organic matter or soil carbon (up to 28% in 22 years) leading to increased (up to 50% more) percolation of water. Surface runoff decreases as water percolation improves. In drought years organic systems produced higher corn and soybean yields (28 to 34%) based on better water delivery from the improved soil organic matter content. Long term studies of regenerative/organic farming systems and practices show their clear potential for conserving and improving surface and ground water resource quality.

 

Background

 

Since 1981, The Rodale Institute® (TRI) has compared conventional and organic corn and soybean production systems in its Farming Systems Trial for system effects on yields, economic returns, and environmental performance (Petersen et al., 1999). In this trial Conventional corn and soybean row crop rotation depends on synthetic fertilizer and herbicides applied according to current recommendations of Pennsylvania State University Cooperative Extension Service (CONV). In addition, to conventional corn and soybean system  there are two organic management systems compared. There are two organic systems.  These are: 1) a cash grain corn, soybean and wheat rotation with legume and grass cover crops to provide nitrogen and weed suppression (ORG LEG). 2) a mixed farming system that uses manure and legume crops as crop nutrient sources in a 5 year corn, soybean, silage corn, wheat, and hay rotation (ORG MAN). Since 1993, in their Compost Utilization Trial, TRI investigators have compared the long term effects of composts, manure, and conventional fertilizer on yield of corn, wheat and vegetables as well as soil quality, farm economics, and environmental effects of these practices (Reider et al., 2000).

 

In 1991, lysimeters, devices which collect water moving past the crop root zone were installed in FST and in 1993 they were installed in CUT. From 1991 to 2003 samples were collected from 90 lysimeters 15 to 20 times per year giving thousands of water quality observations. Together these important trials offer unique and valuable information on how agricultural practices impact water quality.

 

Nitrate Leaching Findings

 

Twenty percent  of the conventional corn and soybean row crop system samples exceeded the 10 ppm limit for healthy drinking water while only 10 and 16% of the organic manure or cash grain systems exceeded the same limit.

 

Leached total nitrate for raw dairy manure, conventional synthetic fertilizer and broiler litter leaf compost were 100, 75, and 33 lbs per acre, respectively, over the 1994 to 2003 time period.

 

Herbicide Leaching Findings

 

In the conventional corn and soybean production system all water samples exceeded the 0.1 ppb level shown to cause sexual alterations in male frogs (Hayes et al 2002). In corn after corn conventional plots leachates samples occasionally exceeded the 3 ppb allowable concentration for municipal water set by USEPA. Metolachlor was also detected at 0.2 to 0.6 ppb range for steady detection in conventional corn and soybean and occasionally peaked over 3 ppb similar to atrazine. No sideward movement of herbicide was found into adjacent organic plots where herbicides were never detected in leachate.

 

Soil Carbon Findings

 

From 1981 to 2002 increases in soil carbon were 8, 16 and 28%  for the conventional corn and soybean and organic legume and manure systems, respectively. In the CUT even higher accumulation of soil carbon was found for compost but not for synthetic fertilizer or raw manure.

 

Soil carbon increases are associated with improved soil aggregation and water infiltration. Organic systems improved percolation rates up to 50% in some cases. This meant lower runoff and soil erosion.

 

 

 

 

Conclusions

 

Through sensible farm practices, farmers can improve water quality on their farms and for surrounding areas.

 

Nutrient losses are found in many agricultural practices. However these losses are much less with compost compared to raw manure and synthetic fertilizer.

 

Systems (mixed cropping) and practices (compost additions) can build soil carbon or organic matter. This increases soil aggregation and soil water percolation. The result of this change is increased aquifer recharge and reduced soil erosion losses.

 

Although all systems and practices produce similar high yield in absence of drought stress, organic systems produced higher corn and soybean yields than conventional corn and soybean row crops under drought.

 

In conventional farm systems, commonly used herbicides are transferred to soil and ground and surface water. This danger is eliminated in organic production systems.