Originally used to prevent scale in boilers, carpramid or thermal polyaspartate (copoly[(3-carboxypropionamide)( 2-carboxylmethyl) acetamide)] was brought to agriculture under the trade names AmiSorb and Magnet. It claimed to increase nutrient uptake through artificially increasing the volume of soil occupied by roots through increased root branching and root hair development. Under controlled hydroponic or greenhouse conditions, the use of carpramid increased nutrient uptake, some yield determining factors such as wheat tillering and in some cases, crop yield. Extensive field testing from 1996 to 1998 under various nutrient regimes, placements, forms, and timings resulted in very inconsistent performance. Averaged across all experiments for which data were available, small yield increases were observed for corn (+1.75 bushels/acre), soybean (+0.63 bushel/acre), wheat (+1.07 bushels/acre), and grain sorghum (+0.32 bushel/acre), but at best only about one-fourth of the experiments (27 percent for corn and wheat) showed statistically significant yield increases. Across all crops, only three experiments showed an economic advantage to using carpramid. An attempt was made to better define the conditions when responses were observed but no clear pattern emerged that would allow improved probability of predicting a positive response.https://lib.dr.iastate.edu/extension_pubs/1225/thumbnail.jp
