State and Drivers of Productivity as Components of Cropping System Sustainability.

Agricultural system sustainability is comprised of energy, water, soil, plant, economic, sociologic, environmental and other components. The independent and often interacting relationships among several of these components is reflected in the simple measure of crop productivity. Therefore, dissecting “crop productivity” can provide useful information for quantifying the driving forces of cropping system sustainability. Our interdisciplinary team evaluated Status Quo, Soil Conserving, Soil Improving, Disease Suppressive, and Continuous Potato cropping systems under both irrigated and rainfed management to identify and quantify the “state” and “drivers” of productivity in these systems. The Soil Improving System resulted in increased soil aggregate stability, lower soil bulk density, and lower resistance to penetration. Under rainfed management, highest Leaf Area Index (LAI) was obtained in the Soil Improving System, and lowest LAI was observed in a Continuous Potato System in all three study years. Similarly, highest Leaf Area Duration was found in the Soil Improving System. These results indicate that management practices focused on improving the soil resulted in potato plant canopies with greater and longer lasting photosynthetic potential. This translated into higher yield, where the Soil Improving System under rainfed management increased potato yield by 91-162 kg/ha compared to Continuous Potato. Similar increases in plant growth and yield were observed with irrigation of Continuous Potato. These results show that water was the primary driver of potato productivity, and that management practices to improve soils can substitute for irrigation in removing this constraint to productivity in the cool, humid Northeast.