The optimal plant density of maize for dairy cow forage production

Abstract

Whole maize (Zea mays L.) plant (WMP) silage is an important feed for dairy cows. In northern China, yields and feed quality are adjusted by modifying the planting density. This paper is the result of a 2-yr field study aimed at determining the effects of plant density on maize silage yield and quality. Five planting densities (52,500, 60,000, 67,500, 75,000, and 82,500 plants ha−1) were used. The results showed that plant height and leaf area increased, while stem diameter, chlorophyll, and leaf area per plant decreased with increasing plant density. Both the biomass yield, expressed as the dry matter (DM) per ha, and the utilizable energy yield improved when the density was increased from 67,500 to 75,000 plants ha−1, but increasing the density further reduced these values. The highest observed DM were 17,734 kg ha−1 and 17,055 kg ha−1, and total net energy for lactation (NEL) were 104.1 GJ ha−1 and 97.0 GJ ha−1 in 2017 and 2018, respectively. Feeding quality generally decreased with increasing plant density. The plant density which obtained the highest biomass yield was not the same as the plant density for optimizing feeding production. Compared with the highest predicted DM yields, the highest predicted total NEL yields increased the grading index by 4–9%, which indicated an improvement in forage quality. Total NEL yield is more efficient for the purpose of evaluating the productivity of WMP forage than biomass yield.