The performance of organic and conventional cropping systems in an extreme climate year.
D.W. Lotter, R. Seidel, and W. Liebhardt
American Journal of Alternative Agriculture
Volume 18, Number 2, 2003

Abstract. The 1999 severe crop season drought in the northeastern US was followed by hurricane-driven torrential
rains in September, offering a unique opportunity to observe how managed and natural systems respond to climate related
stress. The Rodale Institute Farming Systems Trial has been operating since 1981 and consists of three replicated
cropping systems, one organic manure based (MNR), one organic legume based (LEG) and a conventional system
(CNV). The MNR system consists of a 5-yr maize/soybean/wheat/clover/hay rotation, the LEG of a 3-year maize/
soybean/wheat/green manure, and the CNV of a 5-yr maize/soybean rotation. Subsoil lysimeters allowed quantification
of percolated water in each system. Average maize and soybean yields were similar in all three systems over the post transition
years (1985-1998). Five drought years occurred between 1984 and 1998 and in four of them the organic
maize outyielded the CNV by significant margins. In 1999 all crop systems suffered severe yield depressions; however,
there were substantial yield differences between systems. Organic maize yielded 38% and 137% relative to CNV in the
LEG and MNR treatments, respectively, and 196% and 152% relative to CNV in the soybean plots. The primary
mechanism of the higher yield of the MNR and LEG is proposed to be the higher water-holding capacity of the soils in
those treatments, while the lower yield of the LEG maize was due to weed competition in that particular year and treatment.
Soils in the organic plots captured more water and retained more of it in the crop root zone than in the CNV
treatment. Water capture in the organic plots was approximately 100% higher than in CNV plots during September's
torrential rains.

Key words: organic agriculture, organic farming drought resistance, crop water, hydrology