Crop Residue Management Strategies to Reduce Nitrogen Losses during the Winter Leaching Period after Autumn Spinach Harvest

Abstract

In open-field vegetable production, high quantities of soil mineral nitrogen (Nmin) and N-rich crop residues often remain in the field at harvest. After the harvest of crops in autumn, this N can lead to considerable nitrate (NO3−) losses during the subsequent winter leaching period. In four field trials, different tillage depths (3–4, 10, 30 cm) and dates (early autumn, late autumn, early spring) were investigated to reduce N losses after growing spinach in the autumn. In a further treatment, the nitrification inhibitor 3,4-Dimethylpyrazole phosphate (DMPP) was directly applied to the crop residues. Potential N losses were calculated by a balance sheet approach based on Nmin concentration (0–90 cm), measured N mineralization and N uptake by catch crops. By postponing the tillage date from early to late autumn or spring, resprouting spinach stubbles acted as a catch crop, reducing N losses by up to 61 kg ha−1. However, if the spinach biomass collapsed, the N losses increased by up to 33 kg ha−1 even without tillage. The application of DMPP as well as the tillage depth were less effective. Overall, postponing tillage to spring seems to be the most promising approach for reducing N losses during the off-season.

Aporte de carbono y nitrógeno al suelo por residuos de cultivos forrajeros alternativos

“…En otros estudios se indica que estos niveles de N y C/N provocan que se presente en el suelo el proceso de inmovilización temporal de N de la solución del suelo por microorganismos, el cual retrasa la mineralización del N contenido en los residuos (Alghamdi et al, 2022) y esto ocurre porque los requerimientos de N de los microorganismos del suelo no son cubiertos por los residuos de cosecha (Gezahegn, 2017). Los valores de C/N en los residuos de las especies alternativas (canola, remolacha, brásicas, rábano, garbanzo y trébol Alejandrino) (Cuadro 2) fueron similares a los observados en otros estudios realizados con veza vellosa (9-9.9), trébol rojo (10.3 a 14.5), rábano forrajero (15.1 a 15.7), canola (24) (Finney et al, 2016); chícharo (9), trébol (13) (Pereira et al, 2017); espinaca (9.6) (Frerichs et al, 2022); lenteja, garbanzo, frijol gandúl (17.7-19.5) (Singh et al, 2021); chícharo (18) y rábano forrajero (8) (Alghamdi et al, 2022). Los residuos de estos cultivos, con alto contenido de N y valores bajos de C/N presentan una descomposición y liberación de N más rápida e intensa, con valores máximos entre los 42 y 56 días después del inicio de descomposición (Singh et al, 2021;Alghamdi et al, 2022); posteriormente, los valores declinan a los 60-90 días (Singh et al, 2021).…”