Fertilization of K is very important to increase product agriculture besides fertilization of N and P. In this time usage fertilizer not yet proportional and rational, such as those which happened in usage rice field fertilizer of K for the crop of paddy tend to excessively. The other way in the upland needing more fertlizer but fertilized slimmer or is not fertlized K. Proportional and rational fertilization can reach if pay attention the nutrients dynamics and soil status, and also requirement of nutrient for this crop to reach optimum production. This approach can be executed better and profit if fertilization recommendation based on by result of research soil testing. Research goal to to determine requirement of K fertilizer for maize in Typic Kandiudox. The experiments used split-plot design, as main plot are five status nutrients and as sub plot are five treatments of K levels, three replications. The levels of K treatment were 0, 20, 40, 80, and 160 kg K/ha from KCl fertilizer and as indicator crop was maize cultivar P-12. The result showed that NH4OAc. pH 4,8, NH4OAc. pH 7,0, and HCl 25% were selected extraction methode to estimate K fertilizer requirement for Maize (Zea mays L.) in Typic Kandiudox and NH4OAc. 1 N pH 4,8 was the best extractan, because get highest coefisien corelation. The K status can be grouped into three classes of availability of K are low, medium, and high with the critical limit for each extractan are 5,0; 10,0; dan 130 mg kg-1 K2O for NH4OAc. 1 N pH 4,8, NH4OAc. 1 N pH 7,0, and HCl 25 % extractants respectively. Optimum dosages of K fertilizer was 150 kg ha-1 and 75 kg ha-1 KCl each for the low and medium status and do not be fertilized for the high status.
Total content of potassium in smectitic soils is commonly high, however its availability for plant growth is frequently problem because it is fixed at interlayer space of 2:1 type of clay mineral. The research was aimed to study the sorption and effect of Na+, NH +, and Fe3+ on soil available K at smectitic soils. It was conducted in Laboratory of Research and Soil Test, Indonesian Soil Research Institute by using four of soil samples taken from Bogor (Typic Hapludalfs), Cilacap (Chromic Endoaquerts), Ngawi (Typic Endoaquerts), and Blora (Typic Haplustalfs). Incubation experiment used Randomized Completely Block Design, 4 treatments, and 5 replications. The treatment consisted of without cation, application of Na+, NH +, and Fe3+ from NaCl, NH Cl, and FeCl respectively at 50% of maximum adsorption level. The results showed that soil sorption, buffering capacity, and maximum sorption of Fe3+ were higher than NH + and Na+, while the variables of NH + were similar with those of Na+. Among the treatments,bond energy constant was in order of Na+ > Fe3+ > NH + at Alfisols and it was in order of Fe3+ > Na+ > NH + at Vertisols. Among the soils, the soil sorption, buffering capacity, and maximum sorption were in order of Vertisols > Alfisols. The application of Na+ significantly increased soil soluble-K at Chromic Endoaquerts and Typic Endoaquerts; NH + significantly increased soil exchangeable K at Typic Hapludalfs, Chromic Endoaquerts, and Typic Endoaquerts; while Fe3+ significantly increased both variables in all tested soils.
The research objective was to determine the best soil P extraction method for shallot plants in Ultisols. This study used a single location approach. The selected location was in Kentrong village, Malangsari Village, Cipanas, Lebak, Banten Province. The research was conducted from March 2015 to May 2016, consisting of two stages, namely the creation of P nutrient status and correlation testing through planting in polybags in a greenhouse. Preparation of soil P nutrient status using phosphoric acid (H3PO4) from very low to very high (0X, 1 / 4X, 1 / 2X, 3 / 4X, and X), where X is half of the maximum absorption of 1033.3 kg P ha−1 . Fertilizer P was incubated for three months, then taking soil samples in each plot for analysis of soil P content. Soil P content analysis used five different extraction methods, namely Bray I (0.025 N HCl + 0.03 N NH4F solution), Bray II (NH4F 0.03 N + HCl 0.10 N), Mehlich I (0.0125 M H2SO4 + 0.05 M HCl), Morgan Wolf (NaC2H2H3O2.3H2O; pH 4.8), and Truog (0.02 N H2SO4 + (NH4) 2SO4). The planting of shallots in polybags was carried out in the greenhouse of Jakarta Assessment Institute for Agricultural Technology, using a completely randomized design (CRD), with five replications. The results showed that the best soil P nutrient extraction method for shallot plants in Ultisols was the Truog method with a correlation coefficient of 0.77 and 0.84 for the correlation between soil P content and relative yields of plant dry weight and the correlation between soil P content and Uptake P. The results of this study can be used to determine recommendations for P fertilization on shallots in an Ultisol soil.
The P calibration test was carried out from March 2015 to January 2016, the selected location was in Kentrong Village, Malangsari Village, Cipanas, Lebak, Banten Province. The research objective was to determine the recommendation for P fertilization of shallot plants in Ultisols using soil testing, with a single location approach. The study used a split-plot design with 5 replications.The main plot treatment was the soil P nutrient status, namely 0X, 1 / 4X, 1 / 2X, 3 / 4X, and X, where X is half the value of nutrient absorption P of 1033.3 kg P ha−1. The P application used phosphoric acid (H3PO4), the dosages of each level were 0, 258.3, 516.65, 775, and 1033.3 kg P ha−1, equivalent to 0, 0.97, 1.94, 2.9, and 3.87 kg P plot−1. Fertilization of P in subplots using SP-36, the doses of P fertilizer for subplots were 0, 591.6, 1183.3, 1774.9, and 2366.6 kg P2O5 ha−1, equivalent to 0, 0.44, 0.89, 1.33, and 1.77 kg P2O5 plot−1. The results showed that the interval limits for the availability of P nutrients extracted with Truog for very low, low, medium, high and very high classifications were <1, 1 - <9, 9 - <28, ≥ 28 ppm P. Maximum requirement for P fertilizer for shallot plants in ultisol soils in low and medium nutrient availability classes are 1850 kg P2O5 ha−1 and 1310 kg P2O5 ha-1. The optimum requirement for P fertilizer is 1315 kg P2O5 ha−1 and 765 kg P2O5 ha−1
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