Abstract
Agricultural waste, such as sago waste (SW), is one of the sources of pollution to streams and rivers in Sarawak, particularly those situated near sago processing plants. In addition, unbalanced and excessive use of chemical fertilizers can cause soil and water pollution. Humic substances can be used as organic fertilizers, which reduce pollution. The objectives of this study were to produce K- and ammonium-based organic fertilizer from composted SW and to determine the efficiency of the organic-based fertilizer produced. Humic substances were isolated using standard procedures. Liquid fertilizers were formulated except for T2 (NPK fertilizer), which was in solid form. There were six treatments with three replications. Organic fertilizers were applied to soil in pots on the 10th day after sowing (DAS), but on the 28th DAS, only plants of T2 were fertilized. The plant samples were harvested on the 57th DAS during the tassel stage. The dry matter of plant parts (leaves, stems, and roots) were determined and analyzed for N, P, and K using standard procedures. Soil of every treatment was also analyzed for exchangeable K, Ca, Mg, and Na, organic matter, organic carbon, available P, pH, total N, P, nitrate and ammonium contents using standard procedures. Treatments with humin (T5 and T6) showed remarkable results on dry matter production; N, P, and K contents; their uptake; as well as their use efficiency by maize. The inclusion of humin might have loosened the soil and increased the soil porosity, hence the better growth of the plants. Humin plus inorganic fertilizer provided additional nutrients for the plants. The addition of inorganic fertilizer into compost is a combination of quick and slow release sources, which supplies N throughout the crop growth period. Common fertilization by surface application of T2 without any additives (acidic and high CEC materials) causes N and K to be easily lost. High Ca in the soil may have reacted with phosphate from fertilizer to form Ca phosphate, an insoluble compound of phosphate that is generally not available to plants, especially roots. Mixing soil with humin produced from composted SW before application of fertilizers (T5 and T6) significantly increased maize dry matter production and nutrient use efficiency. Additionally, this practice does not only improve N, P, and K use efficiency, but it also helps to reduce the use of N-, P-, and K-based fertilizers by 50%.
Highlights
The main product of the sago palm (Metroxylon sagu) is starch
The selected chemical and physical properties of Bekenu series (Tipik Tualemkuts) were relatively different from those reported by Paramanathan[26] (Table 1) because this soil has been cropped for some time
Neutral pH, high organic matter, and cation exchange capacity (CEC) of the humin may have loosened the soil as well as improving nutrient retention when applied to soils
Summary
The main product of the sago palm (Metroxylon sagu) is starch. The state of Sarawak, Malaysia at present is the principal producer of sago, exporting about 25,000 to 40,000 tonnes of sago starch annually[1]. For every 100 kg of sago starch in pith (70–90 kg can be extracted), there is 10 kg of waste[2]. SW is likely to be discarded into rivers because most of the factories are built near riversides. Inefficient starch extraction will contribute to large amounts of waste[3]. This quantity may be greater if the extraction efficiency is low as sugars, proteins[2], and starches can create high BOD and COD levels in the river[4]. Some researchers have used SW as a substrate for cultivation of edible mushrooms[5], animal feed, production of enzymes[6] and absorbents[7], to reduce this waste
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