Agronomic evaluation of unacidulated and partially acidulated Minjingu and Chilembwe phosphate rocks for clover production in Ethiopia

• Published in: European journal of agronomy Vol. 10; no. 1; pp. 37 - 47
• Main Authors: Haque, I., Lupwayi, N.Z., Ssali, H.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 1999; Elsevier Science
• Subjects: ACIDULANT; ACIDULANTES; ACIDULANTS; Agronomy. Soil science and plant productions; Annual clover; APPROPRIATE TECHNOLOGY; Biological and medical sciences; EFFICACITE; EFFICIENCY; EFICACIA; ETHIOPIA; ETHIOPIE; ETIOPIA; FOSFATO MINERAL; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; HIGHLANDS; Nitrogen, phosphorus, potassium fertilizations; Partial acidulation; Phosphare rock; PHOSPHATE NATUREL; Phosphorus fertilization; REGION D'ALTITUDE; RENDEMENT; RENDIMIENTO; ROCK PHOSPHATE; Soil-plant relationships. Soil fertility. Fertilization. Amendments; SUPERFOSFATO; SUPERPHOSPHATE; TECHNOLOGIE APPROPRIEE; TECNOLOGIA APROPIADA; TRIFOLIUM; Tropics; VERTISOL; VERTISOLES; VERTISOLS; YIELDS; ZONA DE MONTANA; East Africa; Sub-Saharan Africa; Ethiopia; Africa; Phosphare rock; Tropics; Annual clover; Partial acidulation; Vertisol; Plant production; Macronutrient(mineral); Tropical zone; Available nutrient; Phosphorus; Phosphate fertilizer; Phosphorus fertilization; Solubilization; Tropical soil; Vertisols; Leguminosae; Dicotyledones; Phosphate rock; Angiospermae; Spermatophyta; Yield; Fodder crop; Acid medium
• ISSN: 1161-0301; 1873-7331
• DOI: 10.1016/S1161-0301(98)00048-3

Most soils in sub-Saharan Africa are P deficient, but the high cost of water-soluble P fertilizers limits the use of P fertilizers by resource-poor farmers. A low-cost alternative is to apply phosphate rocks. We evaluated the effectiveness of unacidulated (PR), 25% partially acidulated (PAPR25), and 50% partially acidulated (PAPR50) Minjingu and Chilembwe phosphate rocks relative to triple superphosphate (TSP) on
Trifolium quartinianum grown on a Vertisol in the Ethiopian highlands. The fertilizers were applied once at 0–80
kg P
ha
−1 and their effects were followed in four consecutive clover crops. In the Minjingu phosphate rock experiment, clover DM yields without applied P were below 1
t DM
ha
−1 in all except the first of four consecutive crops. With P application, herbage yields reached as high as 14
t
ha
−1. Significant (
P<0.05) effects of P on clover DM and P uptake were observed at least up to crop 3. Over all the four crops, PR was 114%, PAPR25 was 113% and PAPR50 was 107% as effective as TSP in increasing clover herbage yields. The corresponding relative responses in P uptake were: 128, 121 and 112% for PR, PAPR25 and PAPR50, respectively. The substitution rates in herbage yields were: 130% for PR, 128% for PAPR25 and 114% for PAPR50 while those for P uptake were 164% for PR, 146% for PAPR25 and 125% for PAPR50. In the Chilembwe phosphate rock experiment, clover DM yields without applied P were below 1.3
t DM
ha
−1 in the five years of the study. With P application, herbage yields reached as high as 7
t
ha
−1. Significant effects of P on clover DM and P uptake were observed only in the first two crops. Over all the five crops, PR was 27%, PAPR25 was 57% and PAPR50 was 73% as effective as TSP in increasing clover herbage yields. The corresponding relative responses in P uptake were 18, 49 and 59% for PR, PAPR25 and PAPR50, respectively. The substitution rates in herbage yields were 7% for PR, 32% for PAPR25 and 53% for PAPR50 while those for P uptake were 3% for PR, 24% for PAPR25 and 35% for PAPR50. It was concluded that raw Minjingu phosphate rock is highly effective on clover in these Vertisols and partial acidulation is not necessary, but raw Chilembwe phosphate rock is ineffective and 50% partial acidulation is recommended.