EFFECT OF WONDERGRO- A SOIL CONDITIONER FOR ENHANCING DI- AMMONIUM PHOSPHATE (DAP) USE EFFICIENCY IN MAIZE PRODUCTION

Abstract

Despite maize being considered a staple food crop in Kenya, its productivity is low mainly due to inappropriate soil fertility management, especially in smallholder systems. The continuous decline in soil fertility is a consequence of acidic conditions, nutrient imbalances, and sub-optimal fertilizer use, causing depressed maize yield. Use of balanced and adequate fertilizers while improving other soil conditions is a prerequisite for increasing fertilizer use efficiency and maize production. On-farm trials were conducted during the long and short rains seasons of 2023 & 2024 to asses’ performance of two formulations of WonderGro (WG3 & WG21)- a soil conditioner- in combination with the commonly applied Di-Ammonium Phosphate (DAP) fertilizer on maize yield and the economic return, under a range of soil pH (sub- optimal (pH<5.5) and optimal (≥5.5)) for maize production. Sixteen (16) study sites located in two agroecological zones (AEZ), of medium potential (western Kenya) and high potential (Rift Valley), with expected maize grain yields of 4.5-5t ha- 1

and 6-8t ha-1

, respectively, were selected for the on-farm trials. Each AEZ had eight (8) sites equally distributed in two (2) counties. The trials involved five treatments: 0 kg DAP ha-1 (absolute control), 133 kg DAP ha1 (full rate of recommended DAP application per ha-1

), 67 kg DAP ha-1 (half rate of recommended DAP

application per ha-1

), 67 kg DAP+WG3 ha-1

and 67 kg DAP+WG21 ha-1,

each replicated four (4) times. Maize production in the medium potential AEZ, in the sub-optimal pH category, use of half rate of DAP in combination with WG3, slightly increased yield by 3.5% from the use of the full rate of DAP (133kg DAP ha-1

), with 2.8tha-1

of maize grain yield in the long rains of 2024. While in high-potential AEZ, suboptimal pH for maize production (<5.5), applying 67 kg DAP + WG21 ha-1

slightly increases yield to 5.1t ha-1 from 5.0t h-1 with application of the full rate of DAP. In high AEZ, there was no variation in maize grain yield in optimal pH, regardless of fertilizer applied, with an average of 7.3 t ha-1 and 6.1t ha-1 for 2023 and 2024 long rains, respectively. Economically, application of 67kg DAP ha-1 +WG21 had the largest Value Cost Ratio (VCR) of 7.54 and 8.24 for long rains 2023 and 2024, respectively, in sub-optimal pH in the high-potential zone. The formulations, therefore, have the potential to boost yield and for better economic returns to the farmers.