Paulo Cesar Ocheuze Trivelin

Foliar N‐fertilization (FNf) has emerged as a promising approach to synchronize plant nitrogen (N) demands and application timing, reducing the N losses to the environment associated with traditional soil‐based fertilization methods. However, limited information exists regarding the effectiveness of FNf in sugarcane. This study aimed to optimize FNf in sugarcane by evaluating N‐fertilizer recovery by the plant (NRP) and assessing potential toxicity effects. Four sugarcane genotypes were subjected to FNf using ¹⁵N‐urea at five nitrogen concentrations. NRP was assessed at five time points for roots, stalk, old leaves, ¹⁵N‐urea‐fertilized leaves (¹⁵NL), and unexpanded leaves (UEL). Leaf scorching, indicating FNf toxicity, was analyzed using morpho‐anatomical and histochemical techniques. The results showed that FNf promoted high NRP, with an average recovery of 62.3%. Surprisingly, the redistribution of ¹⁵N‐urea did not follow the nitrogen uptake rate by sugarcane leaves, with an average of 41.3% of the total‐NRP. The stalk emerged as the primary sink for ¹⁵N‐urea, followed by the UEL. Genotypes differed in the leaf scorching intensity, which increased with higher concentration of ¹⁵N‐urea. Genotypes also differed in the ¹⁵N‐urea uptake rate, down‐regulated by the N content in the ¹⁵NL. These findings emphasize that by carefully choosing the appropriate genotype and nitrogen concentration, FNf can significantly enhance N‐fertilizer uptake, resulting in potential environmental and economic benefits.

The use of ¹⁵N tracers in blends of N-fertilizers contributes to determining the N derived from each N-fertilizer in the plant, improving the recommendation in the field. However, to evaluate the contribution of two ¹⁵N-labeled fertilizers to maize nutrition is an expensive process, and it is challenging to manufacture ¹⁵N-labeled controlled-release urea (CRU) considering a polymer-sulfur coated urea (PSCU). The objective of this study was to evaluate, in a field experiment, two methods to quantify the N derived from the PSCU (NdfPSCU) in maize plant using two blends (70% PSCU + 30% urea (U) and 30% PSCU + 70% U) applied in three ways (incorporated, broadcast and split application). The first method quantifies the NdfPSCU by subtracting the total N uptake in the N treatment by the sum of the N uptake in the control treatment (without N-fertilizer application) and the N derived from the U (NdfU) in the plant quantified with ¹⁵N. The second method quantifies the NdfPSCU using ¹⁵N (precise and direct method). Despite the first method is less expensive than the second it underestimated the NdfPSCU in four maize growth stages in Rhodic Eutrustox soil, being necessary the use of ¹⁵N in the PSCU to quantify the NdfPSCU with blends of PSCU + U.

This study evaluated the productivity and nutrient concentrations of organic cherry tomatoes and leguminous green manures grown in intercropping systems in rotation with maize. The experimental design was a complete randomised block design with five replications and eight treatments, as follows: monocrop of cherry tomato adding residual maize crop residue (straw) as a mulch (control), monocrop of cherry tomato without the addition of maize crop residue (control), cherry tomatoes intercropped with jack bean, sun hemp, dwarf velvet bean, mung bean, white lupin or cowpea bean grown as green manures. In this production system, which was evaluated between 2011 and 2013, maize was cultivated from January to April, and the cherry tomatoes, with or without leguminous green manures, were grown from May/July to November/December. The number and weight of total and marketable fruits of tomatoes were 70% – 88% higher in 2011 than in 2012 and the number of damaged fruits was 12% lower in 2011 than in 2012. In 2011, the weights of total and marketable fruits in the intercropping treatment with white lupin were lower than that in the controls and in the intercropping treatments with dwarf velvet and cowpea bean. The white lupin and sun hemp green manures produced the highest biomass dry weight, followed by the jack bean, cowpea bean, mung bean and dwarf velvet bean. The different treatments had no effect on the yield of the maize.

The aim of this study was to investigate the transfer of N from different legumes to cherry tomatoes in the intercropping system under residual straw of the previous green corn crop using the ¹⁵N natural abundance method. We also investigated the temporal variation in nitrogen transfer to a cherry tomato, the biological nitrogen fixation (BNF) of legumes, and the N concentration of green corn cultivated in the intercrop succession. The experimental design was a complete randomized block with eight treatments and five replications, described as follows: two controls consisting of a monocrop of cherry tomato with or without residual straw, cherry tomato and jack bean, sun hemp, dwarf velvet bean, mung bean, and white lupine or cowpea bean in intercropping system. The BNF was responsible for more than half of the N accumulated in the legumes. The N of legumes was transferred to cherry tomato in similar quantities, and the leaves and fruits of cherry tomato received more N transfer than shoots. It was shown that N transfer increases with the growth/development of cherry tomatoes. The intercropping system with legumes did not affect the ¹⁵N natural abundance of leaves and the aboveground biomass of green corn cultivated in succession.