Organic production system as an alternative to reduce dependence on mineral fertilizers in macunde bean (Vigna unguiculata L.) cultivation on arenosols in the suburban agricultural zone of Luanda

Abstract

The Macunde bean (Vigna unguiculata L.) is a strategic staple food in the diet of the Angolan population, playing a crucial role in food security. This study aimed to demonstrate to producers that, given the scarcity and high cost of mineral fertilizers, satisfactory grain yields can be achieved through the partial replacement of these inputs with locally available organic fertilizers (cattle manure, chicken manure, and plant residue). A field experiment was therefore conducted in Camama, Luanda, using a randomized complete block design (RCBD) with eight treatments and three replications: T1 (plant residue + 100 kg ha⁻¹ NPK); T2 (cattle manure + 100 kg ha⁻¹ NPK); T3 (chicken manure + 100 kg ha⁻¹ NPK); T4 (plant residue only); T5 (cattle manure only); T6 (chicken manure only); T7 (200 kg ha⁻¹ NPK — reference fertilization); and T8 (control, no fertilization). The experiment was conducted on a sandy-textured Arenosol (90% sand, 5% silt, and 5% clay) characterized by low organic matter content (1.54%), a pH in H₂O of 5.52, and a very low available phosphorus content (2.51 mg dm⁻³). The agronomic data collected were subjected to analysis of variance (ANOVA), and means were grouped using the Scott–Knott test at 5% significance. The results showed that treatments combining organic fertilizer with half the NPK dose (T1, T2, and T3) did not differ statistically from the exclusive mineral fertilization reference (T7). This synergistic behavior was evident in grain yield, which exceeded 1.2 t ha⁻¹ in the combinations with cattle and chicken manure, as well as in the other parameters evaluated (plant height, number of pods, and shoot dry matter). It is concluded that integrated organomineral management represents a viable agronomic and economic strategy for Angolan family farmers, reducing production costs without compromising crop productivity.