**1. Introduction**

Maize (*Zea mays* L.) is the third most important cereal crop in Pakistan after wheat and rice [1]. In Northwest Pakistan (Khyber Pakhtunkhwa province), maize ranked second after wheat in its importance [2]. Maize average yield in Northwest Pakistan is too low as compared with the

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average yield ofthe country [3, 4]. Maize is a C4 mode of carbon fixation plant efficiently utilizes inputs, shows rapid growth, producing large quantity of organic matter per unit area [5]. In Pakistan, maize was cultivated on an area of 1059.5 (000 ha) with a total production of 4220.1 (000 tones), while during the same season its area of cultivation and production in the Khyber Pakhtunkhwa Province (semiarid condition) was 463.4 (000 ha) and 858.3 (000 tones), respec‐ tively. Its average yield in Pakistan is 3983 kg ha−1, which is much lower than the other corn growing countries of the world (USA, China, Brazil, Argentina, Canada, Italy, Egypt) [6].

The major problems in the way of increasing yield at farmer's fields are the inappropriate nutrients supply [7–9]. Phosphorus unavailability and lack of organic matter under calcareous soils in semiarid climates are some of the major reasons for low crop productivity [10, 11]. Phosphorus is very important for improving crop growth and yield [12–14]. Phosphorus is a macronutrient that plays a number of important roles in plants. Adequate phosphorus results in higher grain production, improved crop quality, greater stalk strength, increased root growth, and earlier crop maturity [3, 4]. Crop phosphorus nutrition depends on the ability of the soil to replenish the soil solution with phosphorus as the crop removes it and on the ability of the plant to produce a healthy and extensive root system that has access to the maximum amount of soil phosphorus. Application of P fertilizers must be done in a way to maximize the P availability to crops and to minimize the risk that P might be lost to the environment by runoff or erosion. According to [15], phosphorus deficiency symptoms appear in the lower part of the plants and results in (1) decreased leaf number, (2) decreased leaf blade length, (3) reduced panicles/ears/spikes per plant, (4) reduced seeds per panicle/ear/spike, and (5) reduced filled seeds per panicle/ear/spike.

Phosphorus is the second most important crop nutrient after nitrogen that increases crop productivity and profitability on P-deficient soils in Khyber Pakhtunkhwa [4, 10, 11]. Phos‐ phorus has been reported to increase the strength of cereal straw, stimulate root development, promote flowering, fruit production, and formation of seeds, and it hastens maturity of the crops [16]. In most of the cropping system especially under semiarid condition, phosphorus is one of the least available mineral nutrient [17] especially in soils high in CaCO3 [18] and high soil pH [19], which reduces P availability to crops [20, 21]. Because large applied phosphorus application as fertilizer moves in to immobile pools through precipitation reaction with highly reactive Al3+ and Fe3+ in acidic, and Ca2+ in calcareous or normal soil [22]. At least 60% water soluble P fertilizer was more effective in calcareous soils because P uptake by corn plants [23]. Percent utilization fertilizer P and available P content of soil generally decreased with increasing CaCO3 concentration [24]. The use of microorganisms such as phosphate-solubi‐ lizing bacteria (PSB) as inoculants with the seed increases P availability and uptake by the plant [25] by production of organic acid, which reduces the pH of the surroundings rhizosphere [26]. Which either dissolve phosphates as a result of anion exchange or can chelate Ca, Fe, or Al ions associated with the phosphates [22].

Application of organic matter to field crops provides nutrients to the plants, also improves water holding capacity, and helps the soil to maintain better aeration for the seed germination and plant root development [27]. Therefore, the combine use of organic fertilizers along with chemical fertilizers may be utilized as an effective tool to improve growth and increase yields [28]. Applications of organic manures, such as crop residues, animal manures (AM), chicken manures, green manures, composts, farm yard manure, biochar, and ash, increase the benefi‐ cial microbes in the soil and improve soil health and sustainability. Organic fertilizers consisted of farmyard manure, poultry manure, sheep manure, and biofertilizer may be used for crop production as an alternate of inorganic fertilizers [29]. However, most of Pakistani soils comprise <1% organic matter [30], because of lower organic matter added to soils [31, 32]. Pakistan is rich in farm manures with immense livestock population. In Pakistan, about 50% AM is used as fuel and more than 50% is not consumed [33]. Poultry manure mineralizes greater than other manure such as cattle or pig dung: plant absorbed nutrient and utilized rapidly [34]. Basic nutrients required for higher growth and yield of crops contains in poultry manure and increases carbon content, water holding capacity, soil structure, and decreases bulk density [35, 36]. Subsistence farmers should apply organic manure directly to the soil as a natural means of recycling nutrients in order to improve soil fertility and yield of crops [37]. Application of cattle dung increases plant height, leaf area, pod number, pod weight in cowpeas [38] and in maize [39].

average yield ofthe country [3, 4]. Maize is a C4 mode of carbon fixation plant efficiently utilizes inputs, shows rapid growth, producing large quantity of organic matter per unit area [5]. In Pakistan, maize was cultivated on an area of 1059.5 (000 ha) with a total production of 4220.1 (000 tones), while during the same season its area of cultivation and production in the Khyber Pakhtunkhwa Province (semiarid condition) was 463.4 (000 ha) and 858.3 (000 tones), respec‐ tively. Its average yield in Pakistan is 3983 kg ha−1, which is much lower than the other corn growing countries of the world (USA, China, Brazil, Argentina, Canada, Italy, Egypt) [6].

The major problems in the way of increasing yield at farmer's fields are the inappropriate nutrients supply [7–9]. Phosphorus unavailability and lack of organic matter under calcareous soils in semiarid climates are some of the major reasons for low crop productivity [10, 11]. Phosphorus is very important for improving crop growth and yield [12–14]. Phosphorus is a macronutrient that plays a number of important roles in plants. Adequate phosphorus results in higher grain production, improved crop quality, greater stalk strength, increased root growth, and earlier crop maturity [3, 4]. Crop phosphorus nutrition depends on the ability of the soil to replenish the soil solution with phosphorus as the crop removes it and on the ability of the plant to produce a healthy and extensive root system that has access to the maximum amount of soil phosphorus. Application of P fertilizers must be done in a way to maximize the P availability to crops and to minimize the risk that P might be lost to the environment by runoff or erosion. According to [15], phosphorus deficiency symptoms appear in the lower part of the plants and results in (1) decreased leaf number, (2) decreased leaf blade length, (3) reduced panicles/ears/spikes per plant, (4) reduced seeds per panicle/ear/spike, and (5)

Phosphorus is the second most important crop nutrient after nitrogen that increases crop productivity and profitability on P-deficient soils in Khyber Pakhtunkhwa [4, 10, 11]. Phos‐ phorus has been reported to increase the strength of cereal straw, stimulate root development, promote flowering, fruit production, and formation of seeds, and it hastens maturity of the crops [16]. In most of the cropping system especially under semiarid condition, phosphorus is one of the least available mineral nutrient [17] especially in soils high in CaCO3 [18] and high soil pH [19], which reduces P availability to crops [20, 21]. Because large applied phosphorus application as fertilizer moves in to immobile pools through precipitation reaction with highly reactive Al3+ and Fe3+ in acidic, and Ca2+ in calcareous or normal soil [22]. At least 60% water soluble P fertilizer was more effective in calcareous soils because P uptake by corn plants [23]. Percent utilization fertilizer P and available P content of soil generally decreased with increasing CaCO3 concentration [24]. The use of microorganisms such as phosphate-solubi‐ lizing bacteria (PSB) as inoculants with the seed increases P availability and uptake by the plant [25] by production of organic acid, which reduces the pH of the surroundings rhizosphere [26]. Which either dissolve phosphates as a result of anion exchange or can chelate Ca, Fe, or Al

Application of organic matter to field crops provides nutrients to the plants, also improves water holding capacity, and helps the soil to maintain better aeration for the seed germination and plant root development [27]. Therefore, the combine use of organic fertilizers along with chemical fertilizers may be utilized as an effective tool to improve growth and increase yields

reduced filled seeds per panicle/ear/spike.

138 Organic Fertilizers - From Basic Concepts to Applied Outcomes

ions associated with the phosphates [22].

Biofertilizers are known to play a number of vital roles in soil fertility; crop productivity and profitability [40]. Biofertilizers are the products containing living cells of different types of beneficial microbes (bacteria, fungi, protozoa, algae, and viruses). Some of the commonly used beneficial microbes in agriculture include *Rhizobia, Mycorrhizae, Azospirillum, Bacillus, Pseudo‐ monas, Trichoderma, Streptomyces* species. According to [40], beneficial microbes are essential for decomposing organic matter in the soil and increase essential macronutrients (nitrogen, phosphorus, potassium, sulfur, calcium, and magnesium) and micronutrients (boron, copper, chlorine, iron, manganese, molybdenum, and zinc) availability to crop plants. Beneficial microbes also play significant role in solid wastes and sewage management. Beneficial microbes increase plants tolerance to different environmental stresses (drought, heat, cold, salinity etc.) and increase plant resistance to insects and diseases attacks. Beneficial microbes not only improve crop growth and productivity by increasing photosynthesis and producing hormones and enzymes but also improve crop quality by controlling different insects and various plant diseases. Beneficial microbes reduce the use of chemical fertilizers and thereby reduce environmental pollution caused by chemical fertilizers. Beneficial microbes reduce cost of production and so increase grower's income and profitability. Beneficial microbes are therefore very important for increasing crop productivity, profitability, and sustainability. PSB increase the growth and yield of different crops as reported in maize [10, 11, 41] and wheat [42]. The use of beneficial microorganisms (biofertilizers) such as PSB as inoculants with the seed increases P availability and uptake by the plants [25], which are important not only for the reduction of the quantity of chemical fertilizers and environment friendly [43] but also increased crop productivity [41].

As phosphorus and organic matter are some of the major limiting factors for crop production under semiarid condition. Therefore, the application of biofertilizer especially PSB and AM could increase phosphorus availability and crop productivity under semiarid condition. However, there is no research to investigate the interactive effects of AM × PSB × P under semiarid condition. This research work was therefore designed with the objectives (1) to find out suitable AM source, (2) to find out proper P level, (3) to find out proper combination of AM × P, (4) to find out proper combination of AM × PSB, (5) to find out proper combination of P × PSB, and (6) to find out proper combination of AM × PSB × P for improving yield and yield components of maize hybrid (CS200) under the semiarid condition at Peshawar (Paki‐ stan).
