Row Configuration and Soil Amendment Affect Performance of Popcorn (Zea mays L. var. Everta) in Semi-Arid South Africa

Appropriate plant spacing is vital to maximizing marginal field and expediting equitable distribution of applied plant nutrients for improved popcorn yield. Two field experiments were carried out during the summer seasons of 2017/18 and 2018/19 at the North-West University (NWU) research farm, Mafikeng campus. The study investigated the response of popcorn to different rates of compost and NPK 20-7-3 fertilizer and plant spacings in the semi-arid region of South Africa. The trial consisted of twenty treatments laid out as a split-plot in a randomized complete block design (r=3). The main plot and subplot effects were amendment rates (4 and 8 t/ha compost, 90 and 180 kg N/ha, while the unamended field served as the control); and four intra-row spacings (cm): 15×15 (SP1), 20×20 (SP2), 25×25 (SP3), and 30×30 (SP4). Data were collected on growth and yield components. Results showed that popcorn had the highest number of leaves (12.75) in plots fertilized with 8 t/ha compost under SP4, while the tallest plant (205.64 cm) was recorded in plots intra-spaced at SP2 and fertilized with 8 t/ha compost. The leaf area index was highest (5.1) in plots amended with 90 kg N/ha under SP4. The chlorophyll content of popcorn in plots supplied with 90 kg N/ha under SP3 was significantly higher, with 56.1% more than the leaf chlorophyll from unfertilized plots under SP1. Biomass (178.33 g/plant) and ear number (2.08) were highest in plots treated with 180 kg N/ha under SP3. The kernel yield of 3.28 t/ha and harvest index of 0.32 were lowest in unfertilized plots under SP1. Popcorn yield improved in plots amended with 8 t/ha compost at SP2 plant spacing, similar to the observations in fields fertilized with 90 kg N/ha mineral fertilizer. Nevertheless, the provision of balanced nutrients and the eco-friendliness of applying organic fertilizer favoured the preference for the use of compost for promoting increased popcorn production.