## 1 Introduction  
Phosphorus is a macronutrient and plays a vital role in metabolism of plants, roots growth, and plants development. It promotes plant flowering, seed and root development, crop quality, and maturation because of accumulation, transfer, and release of energy in different cellular metabolic processes during degradation and biosynthesis. Phosphorus is absorbed by plants in the form of monovalent (H\({}_{2}\)PO\({}_{4}\)\({}^{-}\)) and divalent (HPO\({}_{4}\)\({}^{2-}\)) orthophosphate anions, primarily during vegetative growth and re-translocation during reproductive stage into fruits and seeds [1]. Low absorption of P at initial growth of most plants causes stunting and slow growth of plant leaves. This process reduces photosynthesis [2]. Phosphorus deficiency in maize causes distinct reddish or purple colors on leaves and vegetative tissues of maize plants because of formation of anthocyanin and concentration of chlorophyll. Additionally, P deficiency begins with older leaves because of movement of P compounds to newer leaves. Severe P deficiency impedes plant root growth and P uptake such that crop yield and quality are statistically reduced [3]. Phosphate availability and use efficiency are very poor in acidic soils especially in Malaysia where most soils are high in Al and Fe [4; 5]. Conventionally, significant amounts of lime and P fertilizers (TSP and rock phosphates) are applied to acid soils to saturate Al and Fe ions in addition to ensuring maintenance of enough plant P available [5; 6]. However, this approach is not economically viable because of increase in plant production cost and leaching of P partly because of unbalanced use of P fertilizers. Excessive use of P fertilizers in agriculture had been implicated in eutrophication of water bodies. Hence, there is a need to amend tropical acid soils with organic materials. Organic amendments have been used in the tropics to increase nutrient uptake [7; 8]. [PERSON] et al. reported that organic matter and soil pH influenced availability of plant P uptake [9]. The CLB used this present study was produced by combusting chicken waste under no oxygen or limited oxygen conditions. Biochars are recalcitrant partly because of their high C and degree of aromatic graphene sheets. The surface chemistry, pore size, and particle size distribution of biochars depend on feedstock type and type of pyrolysis (mainly temperature) used [10; 11]. The CLB used in this present study is reputed of reducing soil acidity because of its relatively high pH and liming effect. Furthermore, because of their high affinity for Al and Fe ions, they fix these ions to stop them from being hydrolyzed to produce more hydrogen ions. This chemical reaction unlocked fixed P to make them available but some of the available P are temporarily trapped in the pores structure of CLB and are adsorbed by the functional groups on the outer surface of the graphene sheets and pores. When a tropical acid soil was amended with CLB, soil total P, available P, organic P, and inorganic fractions of P (soluble-P, Al-P, Fe-P, redundant soluble-P, and Ca-P) increased but soil exchangeable acidity, Fe, and Al ion reduced [12] because of the high reactive surface area of this organic amendment which is known to electrostatically bind exchange cations and anions. The anion exchange capacity of biochars prevents anionic nutrients such as phosphates from being excessively leached into water bodies and this minimizes eutrophication. The high affinity of CLB for Al and Fe ion also minimizes P fixation [12; 13]. Moreover, the high pH of CLB increases soil pH to reverse P fixation by Al and Fe ions besides improving soil CEC and nutrient availability [14]. Although [PERSON] et al. used biochar to improve P availability of TSP, their study did not optimize the use of both biochar and TSP because these materials were not varied [12]. Their study focused only on fixed amounts of TSP and biochar. Hence, there is a need to determine economic rates of biochar and TSP.