Impact of peas (Pisum sativum L.) in crop rotation with maize (Zea mays L.)

Abstract

As part of the Pegada 4.0 project, an experimental field was installed at the Boicilhos estate, Coruche, in 2023. The Pegada 4.0 project, among other objectives, aims to assess the footprint of diffuse pollution, namely that caused by the leaching of nitrogen into the soil, contaminating groundwater and/or watercourses through surface runoff. Maize is the main arable crop in Portugal. As it is a crop with photosynthetic metabolism in C4, maize efficiently uses radiation as well as water. However, this crop is very demanding in terms of nitrogen, making it one of the main limiting factors in production. Increasing the efficiency of N use will have to be seen in a systemic approach, involving a multiannual assessment, considering the crops grown in cultural succession or rotation. The inclusion of legumes in the system will provide greater amounts of this nutrient in organic form in a sustainable way. The experimental field was installed in a normal cultivation plot with an area of 2.5ha, on February 1st, with the “Vada” variety. The soil has a sandy-loam texture (83.3% sand; 12.0 silt; 4.3% silt) 7.5 mg/kg of N in the nitric form and 0.08% of total N. In the cultivation plot, 4 sub-plots with an area of 324m2 (18mx18m) were randomly marked. These sub-plots function as a control, as they were not sown with peas. Development and growth were evaluated by harvesting 12 plants at 36, 43, 50, 57, 71, 78 and 85 days after sowing (DAS). The total dry weight of the crop was also determined in 3 sub-plots of 1m2, and the number of plants, the number of pods, the green and dry weight of the plant, whole pods and, subsequently, husk and grain were recorded. Nutrients in DM were analyzed and nutrient restitutions and exports (N, P, K, Ca, Mg) were estimated. The productive population was estimated at around 66.7 plts/m2±6.5 plts/m2. And the number of pods at 357/m2±31.3/m2. The total DM production was 4159kg/ha, divided into 44.7% by straw, 18.7% by husks and 36.7% by grain. In total, the pods (grain and shell) represent 55.3% of the total dry weight of the crop. The grain has an average of 39.1g N/kg DM, the husks 25.7 g N/kg DM, and the straw (stems and leaves) 27.8 g N/kg DM. Considering the DM of the crop components and the average nutrient contents, it was estimated that the crop restores around 71.6kg/ha of N to the soil and exports, in the form of grain, a total of 59.7kg/ha.