Outputs: Potassium Losses from Agricultural Systems

Potassium (K) outputs comprise removals in harvested crops and losses via a number of pathways. No specific environmental issues arise from K losses to the wider environment, and so they have received little attention. Nevertheless, K is very soluble and so can be leached to depth or to surface waters. Also, because K is bound to clays and organic materials, and adsorbed K is mostly associated with fine soil particles, it can be eroded with particulate material in runoff water and by strong winds. It can also be lost when crop residues are burned in the open. Losses represent a potential economic cost to farmers and reduce soil nutritional status for plant growth. The pathways of loss and their relative importance can be related to: (a) the general characteristics of the agricultural ecosystem (tropical or temperate regions, cropping or grazing, tillage management, interactions with other nutrients such as nitrogen); (b) the specific characteristics of the agricultural ecosystem such as soil mineralogy, texture, initial soil K status, sources of K applied (organic, inorganic), and rates and timing of fertilizer applications. This chapter provides an overview of the main factors affecting K removals in crops and losses through runoff, leaching, erosion, and open burning.

Pengelolaan dan Pemupukan Fosfor dan Kalium pada Pertanian Intensif Bawang Merah di Empat Desa di Brebes

ABSTRACTThe management and fertilization of shallot cultivation in Brebes is very intensive. The purpose of this research was to study crop management and phosphorus (P) and potassium (K) fertilizations of shallot cultivation by smallholder farmers in four villages in Brebes. The data were collected through survey method, interview, and questionnaires to 14 respondent farmers, and analysis of P and K content of farmer's soil samples. The results showed that the cropping index (IP) was 400-500% comprised of three to four times of shallot cultivation and one rice cultivation. The fertilizations of P and K were 22-171 kg of P2O5 ha-1 and 22-213 kg K2O ha-1, respectively, while the recommended rates were 54 kg P2O5 ha-1 and 78 kg K2O ha-1, respectively. This varied fertilizations were not significantly correlated with productions, except fertilization of K with production in rainy season that was significantly correlated at P < 0.05 (n = 14, r = 0.532). The soil P status was very high at all locations and at all depths (0 - 80 cm), while the soil K status ranged from medium to very high. Keywords: nutrient accumulation, nutrient availability, nutrient residue, nutrient status, smallholder farmersABSTRAKPengelolaan dan pemupukan pada budidaya bawang merah di Brebes sangat intensif. Tujuan penelitian ini ialah mengkaji pengelolaan pertanaman dan pemupukan fosfor (P) dan kalium (K) bawang merah yang dilakukan petani di empat desa di Brebes. Pengumpulan data dilaksanakan melalui metode survei, wawancara, dan pengisian kuisioner kepada 14 petani responden, dan analisis kadar P dan K sampel tanah lahan petani responden. Hasil penelitian menunjukkan bahwa indeks pertanaman (IP) adalah 400-500% dengan pertanaman bawang merah tiga sampai empat kali dan satu kali pertanaman padi. Pemupukan P dan K berturut-turut berkisar 22–171 kg P2O5 ha-1 dan 22–213 kg K2O ha-1, sementara rekomendasi Distan Brebes berturut-turut adalah 54 kg P2O5 ha-1 dan 78 kg K2O ha-1. Pemupukan bervariasi ini tidak berkorelasi nyata dengan produksi, kecuali pemupukan K dengan produksi pada musim hujan yang berkorelasi nyata pada taraf 5% (n=14, r=0.532). Status P tanah sangat tinggi pada semua lokasi dan pada semua kedalaman (0 – 80 cm), sementara status K tanah lebih bervariasi, yaitu dari sedang sampai sangat tinggi.Kata kunci: akumulasi hara, ketersediaan hara, petani kecil, residu hara, status hara

Fertility map and horizontal soil potassium status of north-eastern region of Haryana

Considering soil fertility evaluation of any area for sustainable production, an experiment was conducted to investigate the horizontal soil potassium status (K) of the soil surface of north-eastern region of Haryana. The study indicated that available K of surface soil samples ranged from 44 to 867 kg/ha with a mean value of 148 kg/hain Ambala district. In panchkula district it ranged from 44 to 865 kg/ha with a mean value of 138 kg/ha where as in Yamunanagar district K content varied from 62 to 441 kg/ha with a mean value of 147 kg/ha. Maximum K deficient samples were observed at Panchkula district that is 60.5 % followed by Yamunanagar and Ambala, 36.3 and 30.2 % respectively with an overall 41.3% K deficient samples. In case of Ambala 62.8% soil samples were mediumin K fertility and in case of Yamunanagar 52% soil samples were medium in K fertility. Nutrient index value for K was found 1.77, 1.76 and 1.47 in Ambala, Yamunanagar and Panchkula districts, respectively. On the basis of available surface soil K status a horizontal fertility map was prepared using GPS data. K fertilization is strongly suggested with recommended dose to check further depletion of soil available K of the surface layer.

Pengaruh Varietas, Status K-Tanah, dan Dosis Pupuk Kalium terhadap Pertumbuhan, Hasil Umbi, dan Serapan Hara K Tanaman Bawang Merah

ABSTRAK. Pemupukan sebaiknya didasarkan pada kebutuhan tanaman dan kesuburan lahan agar diperoleh hasil yang optimal. Adanya keragaman tanah dan lingkungan yang cukup tinggi di Indonesia menyebabkan kebutuhan pupuk berbeda dari satu lokasi ke lokasi lainnya. Penelitian bertujuan untuk mendapatkan dosis pupuk K optimum untuk dua varietas bawang merah pada status K-tanah yang berbeda. Metode penelitian terdiri atas survei status K-tanah yang dilakukan di sentra produksi bawang merah di dataran rendah Jawa Barat dan Jawa Tengah, dan percobaan pot yang dilakukan di Rumah Kasa Balai Penelitian Tanaman Sayuran Lembang dari Bulan Maret sampai dengan Desember 2008. Rancangan percobaan yang digunakan untuk percobaan pot ialah petak terpisah dengan tiga ulangan. Petak utama ialah bawang merah varietas Bangkok dan Kuning. Anak petak ialah status hara K-tanah, yaitu status K-tanah rendah (&lt;20 ppm K2O), sedang (21–40 ppm K2O), dan tinggi (&gt;41 ppm K2O). Anak-anak petak ialah dosis pupuk K terdiri atas 0, 60, 120, 180, dan 240 kg/ha K2O. Pupuk N (150 kg/ha) dan P (150 kg/ha P2O5) diberikan sebagai pupuk dasar. Hasil penelitian menunjukkan bahwa tidak terjadi interaksi antara varietas, status K-tanah, dan dosis pupuk K terhadap bobot kering tanaman, luas daun, hasil bobot umbi segar, dan bobot umbi kering eskip bawang merah. Namun serapan hara K tanaman dan residu pupuk K dalam tanah dipengaruhi oleh interaksi ketiga faktor tersebut. Hubungan antara hasil umbi bawang merah varietas Bangkok dan Kuning dengan dosis pupuk K pada semua status K-tanah bersifat kuadratik. Dosis pupuk K optimum untuk varietas Bangkok ialah 126,67 kg/ha K2O pada status K-tanah rendah, 170,00 kg/ha K2O pada status K-tanah sedang, dan 1,5 kg/ha K2O pada status K-tanah tinggi, sedangkan dosis pupuk K optimum untuk varietas Kuning ialah 214,29 kg/ha K2O pada status K-tanah rendah, 216,67 kg/ha K2O pada status K-tanah sedang, dan 106,50 kg/ha K2O pada status K-tanah tinggi. Hasil umbi dan serapan hara tanaman varietas Bangkok dan Kuning pada status K-tanah tinggi nyata lebih tinggi dibandingkan pada status K-tanah rendah dan K-tanah sedang. Makin tinggi status K-tanah dan dosis pupuk K, maka makin tinggi pula residu K dalam tanah.<br /><br />ABSTRACT. Sumarni, N, Rosliani, R, Basuki, RS, and Hilman, Y 2012. Effects of Varieties, Soil-K Status, and K Fertilizer Dosages on Plant Growth, Bulb Yield, and K Uptake of Shallots Plant. In order to get the optimum yield, fertilization should be based on plant need of nutrient and nutrient content of soil. The presense of high diversities of soil and environment in Indonesia cause the fertilizer needed are different from one location to another. This research methodologies were survey of soil-K status on some shallots production areas in lowland of West and Central Java, and pot experiment that was carried out at Screenhouse of Indonesian Vegetable Research Institute from March to December 2008. The aim of this experiment was to find out the optimum dosage of K fertilizer for two shallots varieties on several soil fertility level (soil-K status). A split-split plot design with three replications was used in this experiment. As main plots were shallots varieties, consisted of Bangkok and Kuning varieties. Subplots were the content/status of soil-K, consisted of low (&lt;20 ppm K2O), medium (21–40 ppm K2O), and high (&gt;41 ppm K2O). Sub-subplots were K fertilizer dosages, consisted of 0, 60, 120, 180, and 240 kg/ha K2O. N fertilizer (150 kg/ha N) and P fertilizer (150 kg/ha P2O5) were applied as basic fertilizers. The results showed that there were no interaction between varieties, soil-K status, and K fertilizer dosages on plant leaf area, plant dry weight, fresh and dry weight of bulb yield of shallots. But K uptake by shallots plant and residual of K fertilizer in soil were affected by the three those factors. The curves of the relationship between K fertilizer dosages and bulb yield of Bangkok and Kuning varieties on all soil-K status were quadratics. The optimum dosage of K fertilizer for Bangkok variety were 126.67 kg/ha K2O on low of soil-K status, 170.00 kg/ha K2O on medium of soil-K status, and 1.50 kg/ha K2O on high of soil-K status; whereas for Kuning variety were 214.29 kg/ha K2O on low of soil-K status, 216.67 kg/ha K2O on medium of soil-K, and 106.50 kg/ha K2O on high of soil-K status.The bulb yield and K uptake of Bangkok and Kuning varieties were significantly higher on high soil-K status than on low and medium of soil-K status. The more higher of K fertilizer dosages and soil-K status gave the more higher of K residual of K fertilizer in soil.<br /><br />

Availability of soil potassium and diagnostic soil tests

Thirty-seven surface (0–0.10 or 0–0.20 m) soils covering a wide range of soil types (16 Vertosols, 6 Ferrosols, 6 Dermosols, 4 Hydrosols, 2 Kandosols, 1 Sodosol, 1 Rudosol, and 1 Chromosol) were exhaustively cropped in 2 glasshouse experiments. The test species were Panicum maximum cv. Green Panic in Experiment A and Avena sativa cv. Barcoo in Experiment B. Successive forage harvests were taken until the plants could no longer grow in most soils because of severe potassium (K) deficiency. Soil samples were taken prior to cropping and after the final harvest in both experiments, and also after the initial harvest in Experiment B. Samples were analysed for solution K, exchangeable K (Exch K), tetraphenyl borate extractable K for extraction periods of 15 min (TBK15) and 60 min (TBK60), and boiling nitric acid extractable K (Nitric K). Inter-correlations between the initial levels of the various soil K parameters indicated that the following pools were in sequential equilibrium: solution K, Exch K, fast release fixed K [estimated as (TBK15 – Exch K)], and slow release fixed K [estimated as (TBK60 – TBK15)]. Structural K [estimated as (Nitric K – TBK60)] was not correlated with any of the other pools. However, following exhaustive drawdown of soil K by cropping, structural K became correlated with solution K, suggesting dissolution of K minerals when solution K was low. The change in the various K pools following cropping was correlated with K uptake at Harvest 1 (Experiment B only) and cumulative K uptake (both experiments). The change in Exch K for 30 soils was linearly related to cumulative K uptake (r = 0.98), although on average, K uptake was 35% higher than the change in Exch K. For the remaining 7 soils, K uptake considerably exceeded the change in Exch K. However, the changes in TBK15 and TBK60 were both highly linearly correlated with K uptake across all soils (r = 0.95 and 0.98, respectively). The slopes of the regression lines were not significantly different from unity, and the y-axis intercepts were very small. These results indicate that the plant is removing K from the TBK pool. Although the change in Exch K did not consistently equate with K uptake across all soils, initial Exch K was highly correlated with K uptake (r = 0.99) if one Vertosol was omitted. Exchangeable K is therefore a satisfactory diagnostic indicator of soil K status for the current crop. However, the change in Exch K following K uptake is soil-dependent, and many soils with large amounts of TBK relative to Exch K were able to buffer changes in Exch K. These soils tended to be Vertosols occurring on floodplains. In contrast, 5 soils (a Dermosol, a Rudosol, a Kandosol, and 2 Hydrosols) with large amounts of TBK did not buffer decreases in Exch K caused by K uptake, indicating that the TBK pool in these soils was unavailable to plants under the conditions of these experiments. It is likely that K fertiliser recommendations will need to take account of whether the soil has TBK reserves, and the availability of these reserves, when deciding rates required to raise exchangeable K status to adequate levels.

Potassium depletion under long-term fertilization in a semi-arid soil in India

SUMMARYIn 12-year (1975–87) fertilizer trial on a pearl millet-wheat rotation, there were no responses to applied K and exchangeable K decreased from 620 to 200 kg/ha. In spite of progressively diminishing exchangeable K, removal of K by crops was independent of soil K status, indicating that exchangeable K had no relation to K uptake in this soil. Thus, nonexchangeable K made a major contribution to plant K, up to 90% in untreated plots and > 70% in K-treated plots. A significant (r = -·708) relationship between nonexchangeable K and K fixation capacity was found. Nonexchangeable K was also significantly but negatively correlated (r = -0·583) with free energy exchange (ΔGr). Potassium supply values, expressed by pK-½p (Ca + Mg), were positively and significantly correlated with K removal by crops in 1987 and with the K saturation values of the exchange phase, so that both these measures can be successfully used to test soil K availability. The results of this study suggested that on this soil, under a pearl millet-wheat crop system, inclusion of K in the fertilizer programme may soon be needed.

Effects of N and K Fertilizers on Cynodon IB.8 and on Soil K in Southern Nigeria

SUMMARYCynodon IB.8 was subjected to (i) various levels of N under cutting management, and (ii) various levels of K under grazing management. The results indicated significantly higher DM and CP production with 168 kg./ha. of N under cutting management, with resultant significant reduction in exchangeable and non-exchangeable soil K. Under grazing management, increased K application increased K content in the herbage, but showed a negative correlation with Ca uptake. Results indicated that the initial soil K status was adequate to supply the requirements of Cynodon, and that under grazing management the soil K status could be maintained at adequate levels to support lengthy cropping.

Factors influencing the sodium content of meadow grass.

Sodium content of grass was largely determined by Na content and K number of the soil. At a given Na content of soil, the Na content of grass decreased with increasing K number of the soil but the decrease was small where K number was >30. Na content of grass increased with increasing soil Na; the increase was higher at low- than at high soil-K status. K fertilizing lowered grass Na at low soil-K status. Soil-Na content can be used in the Netherlands as a basis for Na-fertilizer recommendations, since K number has generally reached a level at which it has an almost constant effect on Na content of grass. Influences of the K and Na status of the soil on the Na content of grass can be expressed as the ratios (15 X K number)/(Na2O+6) for sandy soils and (25X K number)/(Na2O + 14) for clay soils, the numerator at K numbers > 30 being the same as that at K number=30. With increasing ratios, the Na content of grass decreases. The influence on herbage -Na level of a given amount of Na in K fertilizers is correlated to these ratios. The influence of N fertilizers on Na content of grass was not clear and the influence of Mg fertilizers was negligible. Chile nitrate and Nad affected the Na of grass similarly, but Chile nitrate differed from NaCl in decreasing the Ca content; both fertilizers slightly lowered the Mg content of grass. Herbs and clovers contained more Na than grass does. (Abstract retrieved from CAB Abstracts by CABI’s permission)