A visual for water movement and pore size:
The different straw sizes represent a soil with large pores (coarse textured; A), small pores (fine textured; B) and mixed pore sizes (aggregated; C). Think about how water flows through these straws (or soil pores) and also about how water would rise in each size straw type if you were to cap the end with your finger while placing the other end in water. In the larger straws, the water will not rise as high in the straw versus the smaller straws. Mixed straw sizes will have mixed levels of water rise. This is the same concept for capillary rise in soils of varying texture (A and B) and aggregation levels (C).
A couple of things to keep in mind to improve drainage and water retention:
(1) Good aggregation promotes a diverse pore size distribution which helps with water movement via drainage and also helps retain some of the water for crop use (reduce your level of disturbance by using reduced or no-till to build aggregates)
(2) Roots provide channels for water movement into soils while at the same time use water from multiple depths (diversify your rotations to provide root channels in the soil for water movement – you’ll also get the added benefit of building better aggregation)
(3) Soils in North Dakota formed under grasslands – so think about the water use of the historically diverse grass communities and try to mimic that “balance” in water use and water availability with diverse cropping systems (diverse rotations including some cover crops can use water for a longer period of time while at the same time providing cover to reduce evaporation; check out the Diversity and Intensity Rating worksheet for crop rotations which can be downloaded from:http://www.ag.ndsu.edu/archive/dickinso/agronomy/jons%20worksheet.htm)
See Corn Talk Feb/March 2013 for more detail on water movement accessible through the North Dakota Corn Growers Home Page: