Prolificacy and nitrogen internal efficiency in maize crops

CIAMPITTI, IGNACIO ANTONIO; PARCO, MARTÍN; MADDONNI, GUSTAVO ÁNGEL; D'ANDREA, KARINA ELIZABETH

FIELD CROPS RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2020 vol. 256

0378-4290

In maize (Zea mays L.) crop, defensive practices such as low plant densities and limited nitrogen (N) fertilization have begun to be progressively adopted in limited-production regions of the world. At low plant density,the expression of prolificacy (i.e., more than one fertile ear per plant) can stabilize maize production.Considering N as the main limiting resource, yield can be defined as a function of i) total N uptake and theefficiency to produce yield from total N uptake, i.e., N internal efficiency (NIE) or ii) total N uptake, N harvestindex (NHI) and grain N concentration. The objective of this work was to describe changes in NIE and theirrelated components regulated by prolificacy at both canopy- and plant- scales. Field studies were carried out inBuenos Aires, Argentina, during 2015?2016 and 2016?2017 seasons. Treatments were combinations of two Nsupplies (N-: 0 and N+: 200 kg N ha−1), two plant densities (4 and 8 plants m−2) and five maize hybridsreleased during the last four decades. High N supply positively impacted yield per unit area (ca. 45 %) byincreasing kernel number (ca. 33 %), kernel weight (ca. 18 %) and harvest index (ca. 12 %). At low plant density,high N supply expressed the highest prolificacy (mean 1.65 ears plant−1). The older hybrids displayed thehighest prolificacy (mean 1.30 ears plant−1) and the lowest yield per unit area (mean 792 g m−2), but showedthe greatest grain N concentration (mean 15.1 g kg−1). However, recent hybrids resulted in medium prolificacy(mean 1.11 ears plant−1) with the highest yield per unit area (mean 910 g m−2), but with the lowest grain Nconcentration (mean 13.6 g kg−1). The different pattern of grain N concentration among hybrids coupled withsimilar NHI (mean 0.80) led to the lowest NIE of the most prolific hybrids (mean 55 g yield g N−1) relative to theless prolific ones (mean 60 g yield g N−1). Variations in NIE among genotypes and plant densities were negatively influenced by grain N concentration under N- and under N+ only when prolificacy = 1. Under N+ withprolificacy > 1, NIE variations were positively determined by NHI. For all genotypes, higher yield per plant(mean 30 %) and total N uptake (mean 25 %) were recorded for the prolific plants, reflected in the greaterabsolute NIE (mean 5 %). For the oldest hybrid differences between prolific and non-prolific plants in NIE (mean46.8 vs 41.8 g yield g N-1) were greater than those recorded for the other genotypes due to the higher impact ofprolificacy on yield per plant (mean 51 %) than on total N uptake (mean 26 %). Over time, improvements in NIEprimarily occurred from greater yield of the apical ear. Overall, the expression of prolificacy appears to be anadequate strategy to stabilize maize production in response to improvements of environmental conditions,specially addressed by low plant density and high N supply.