Nitrogen fertilisation impacts greenhouse gas emissions, carbon footprint, and agronomic responses of beet intercropped with arugula.

Although the response of plants to nitrogen (N) in conventional systems has been extensively described in the literature, there is a lack of information available to refine the strategic N fertilisation program required in intercropping systems to match the nutrient supply with crop demands and reduce environmental impacts on greenhouse gas emissions. Therefore, this study aims to investigate the effect of N management on the growth, production, quality, greenhouse gas emissions (GHG) and carbon footprint of a beet-arugula intercropping system during two growing seasons (winter and summer). The efficiency of N fertilisation in each season was assessed by the supply of 20 N doses, varying the amounts applied at planting and as a side dressing (0-80, 0-120, 0-160, 0-200, 0-240, 20-80, 20-120, 20-160, 20-200, 20-240, 40-80, 40-120, 40-160, 40-200, 40-240, 60-80, 60-120,60-160, 60-200 and 60-240 kg N ha-1). GHG emissions and carbon footprint were calculated and converted to CO2 equivalent (CO2 eq) utilising IPCC methodology. The height, total and marketable productivities of beet plants were 33, 31 and 34% higher in winter than in summer, respectively. Arugula plants achieved the highest performance (height, fresh mass and yield) in summer. Considering the environmental impact on global warming/climate change caused by the use of N fertilisers, total GHG emissions may range from 1723.9 to 3369.8 kg CO2eq ha-1 cycle-1 according to the N dose applied. However, based on the carbon footprint, the application of 60-120 kg N ha-1 at planting and as side dressing was the best N dose, since it reduced the carbon footprint (equivalent to 0.134 g CO2eq kcal-1 vegetables) without compromising crop yield.

Effect of population density of lettuce intercropped with rocket on productivity and land-use efficiency.

The objective of this study was to evaluate the influence of the spacing of lettuce rows on the production of a lettuce-rocket intercropping system over two growing seasons (11 August to 25 September 2011 and 12 January to 24 February 2012) in Jaboticabal, São Paulo, Brazil. We evaluated 11 treatments in each season: lettuce-rocket intercrops with five row spacings for the lettuce (0.20, 0.25, 0.30, 0.35 and 0.40 m) and the rocket planted midway between the lettuce rows, sole crops of lettuce at the same five row spacings and a sole crop of rocket. Fresh and dry masses of the lettuce and rocket and number of lettuce leaves per plant were highest with a lettuce row spacing of 0.40 m, but the productivities of the lettuce and rocket were higher with a lettuce row spacing of 0.20 m. The productivities and fresh and dry weights of the lettuce and rocket and the number of lettuce leaves per plant were highest in the sole crops, but the fresh and dry weights of the rocket were higher with intercropping. The land equivalent ratios were >1.0 in both seasons in all intercrops and were highest for the densest crop (1.41). Intercropping was therefore 41% more efficient than sole cropping for the production of lettuce and rocket.