Double‐Annual Forage Crop Rotation Controls Nutrient Surpluses in Nitrogen‐Based Organic Fertilization

• Published in: Agronomy journal 2018-11, Vol.110 (6), p.2268-2276
• Main Authors: Perramon, Bernat, Domingo‐Olivé, Francesc, Bosch‐Serra, Ángela D., Yagüe, María R., Boixadera, Jaume
• Format: Article
• Language: English
• ISSN: 0002-1962; 1435-0645
• DOI: 10.2134/agronj2018.02.0099

Core Ideas In intensive forage systems, 170 kg N ha−1 just from manures limits C sequestration. Biennial rotations of four crops maximize nutrient recirculation in calf‐rearing farms. Double‐annual forage crop rotation reduces P surpluses in crop–livestock systems. The use of organic fertilizers from stock‐raising activity is usually based on the nitrogen (N) criterion. The objective of our research is to evaluate whether this N criterion led to positive or environmentally risky changes, mainly in organic carbon (OC) storage and the availability of the main nutrients. Three biennial rotations of four crops were set up in a 6‐yr time‐frame. The treatments included a control (no N added); two mineral treatments, where 250 kg N ha−1 yr−1 was provided at two different times during the rotation; three cattle manure treatments, which provided 170, 250, and 500 kg N ha−1 yr−1; and four treatments in which the two lowest manure rates were complemented with mineral N (80 and 160 kg N ha−1 yr−1). Over the 6‐yr period, the measured soil OC increases were equivalent to approximately 25, 43, and 35% of the manure OC applied, respectively, following the manure rate increases. Furthermore, equivalences were of −5, 23, and 25% when compared with full mineral fertilization. The positive slope of phosphorus availability was 1.2 mg Olsen‐P kg−1 to 10 kg P ha−1 applied from manures (N/P = 4) when starting from a threshold of 15.9 mg Olsen‐P kg−1. The availability of other nutrients (Mg, Zn, and Na) also increased with increasing manure rates. In a medium‐term experiment, the manure rate of 250 kg N ha−1 yr−1 optimized the nutrient recirculation. In the long term, rotations should be redesigned to control P surpluses, or the amount of N applied from manures should be reduced.