Silicon is a beneficial element for rice plants and is one of the major factors affecting the sustainability of rice production. We investigated silica (Si) availability and dynamics in soils of sawah, other land uses, and also in river and canal water in two watersheds in Citarum and Kaligarang, Java Island, Indonesia. The term sawah refers to a leveled and bounded rice field with an inlet and an outlet for irrigation and drainage, respectively. In the present study, we examined Si content in soils, plants and river water in relation to factors influencing the Si content, such as parent material and land use. The available Si content in sawah was found to be deficient at two sites and low at 10 sites out of 16 sites investigated in the Citarum watershed. In the Kaligarang watershed, no sawah site was classified as deficient and nine out of the 15 sawah sites were determined to be low for rice plant growth. A survey of Si content in rice flag leaves in some selected rice fields showed that seven out of 12 samples had contents less than 125 g SiO 2 kg -1 ; these rice samples with low Si contents were those in sawah classified as low in Si contents. In the Citarum watershed, sawah soils developed from the accumulation of lake and clay sediment contained relatively little available Si, while sawah soils in the Kaligarang watershed that were mainly developed from tuff and volcanic ash contained relatively more available Si. In the Citarum watershed, the type of land use influenced Si availability in the soils via a large amount of litter accumulation of pine trees in the case of pine plantations, and acidification in the soils in the case of tea plantations and maize fields. In general, the Si content in river and canal water was higher in the Kaligarang watershed than in the Citarum watershed, and this appears to be affected by the type of parent material. In addition to the type of parent material, Si depletion occurring in dams might also influence Si content in the lower stream of river or canal water in the Citarum watershed.
Nitrogen fertilizer application rates in intensive vegetable production in (South) East Asia have increased exponentially over the past decades, including in the low income countries. While there have been reports of excessive N inputs from e. g. Vietnam, Thailand and Indonesia, very little quantitative knowledge exists on the real extent of the problem. We calculated N balances and agronomic N use efficiencies (ANUE) for a number of typical intensive vegetable rotations in the highlands of Central Java, Indonesia, on fertile Andisols, both for individual cropping cycles (short term) as for 6 consecutive cropping cycles (long term). This was done for farmers practice (FP) treatments, and improved practice (IP) treatments, where N fertilization was significantly reduced. Yields were in general similar in FP and IP, but tended to be slightly higher in IP, with some significant differences. Both the short and long term N balances were always positive and usually very high. Short term N balances ranged from 9 to 559 kg N ha(-1) and 219 to 885 kg N ha(-1) in IP and FP, respectively, while short term ANUE ranged from 8 to 67 and 4 to 39% in IP and FP, respectively. Long term N balances ranged from 627 to 1,885 kg N ha(-1) and 962 to 3,808 kg N ha(-1) in IP and FP, respectively, indicating a massive excess of N supply especially in FP. N balances can thus be drastically reduced with no negative impacts on yield, on the contrary. Soil mineral N in the 0-25 cm layer was in general not very high (6.5-38.8 mg N kg(-1) soil) and not systematically different between IP and FP, probably as a result of excessive NO(3)(-) leaching. Therefore, topsoil mineral N seems to have only limited indicator value under these conditions. Because denitrification losses in these soils are not very high, most N in excess of the crop requirements will be lost by leaching. Quantitative data on N balances as obtained here may be used to sensitize policy makers and farmers about the threat of current farming practices to the environment, and to improve economic performance
<p><strong>Abstrak</strong>. Beras merupakan makanan pokok bagi bangsa Indonesia dan strategis bagi keamanan pangan nasional. Produksi beras dapat ditingkatkan melalui ektensifikasi lahan, peningkatan mutu intensifikasi dan indeks pertanaman padi. Lahan sawah tadah hujan berpotensi besar untuk menjadi lahan pertanian produktif jika tingkat kesuburan tanahnya ditingkatkan melalui penerapkan pemupukan berimbang sesuai karakteristik tanahnya. Lahan sawah non irigasi seluas 3,30 juta ha, salah satunya adalah sawah tadah hujan. Pengembangan lahan sawah tadah hujan menjadi sangat relavan dengan peningkatan kebutuhan pangan nasional. Makalah ini bertujuan untuk menelaah pengelolaan lahan sawah tadah hujan untuk meningkatkan produksi padi nasional. Faktor pembatas yang sering dihadapi antara lain ketersediaan air hujan yang sulit diprediksi serta kesuburan tanah yang rendah akibat kandungan C-organik dan N-total yang rendah. Kegagalan panen dapat terjadi akibat akibat kekurangan air pada awal tanam musim hujan maupun saat menjelang panen pada musim kedua. Perbaikannya dapat dilakukan dengan tanam gogo rancah pada musim tanam pertama, dan sistem culik pada musim tanam ke dua. Pemberian bahan pembenah tanah seperti kompos jerami, pupuk kandang, <em>biochar</em> dan kapur pertanian/dolomit terutama untuk tanah yang bereaksi masam ditujukan untuk meningkatkan kesuburan tanah sebelum dilakukan pemupukan. Teknologi pemupukan berimbang yang dapat diterapkan pada lahan sawah tadah hujan, antara lain Urea 250-300 kg ha<sup>-1</sup>, SP-36 50-75 kg ha<sup>-1</sup>, dan KCl 50 kg ha<sup>-1</sup>, pemberian bahan organik minimal 2 t ha<sup>-1</sup>, serta pengembalian jerami sisa hasil panen ke dalam tanah. Pemupukan berimbang dapat meningkatkan hasil padi dari 1,8-3,5 t ha<sup>-1 </sup>menjadi 5,0-5,8 t ha<sup>-1</sup>.</p><p> </p><p><strong>Abstract</strong>. Rice is a staple food for the Indonesian people and a strategic comodity for national food security. Rice production can be increased through land extensification, improved quality of intensification and rice cropping index. Rainfed lowland rice fields could be very potentially productive for agriculture when the level of soil fertility is improved by applying balanced fertilization that based on the soil characteristics. Non-irrigated rice field area is 3.30 million ha, including the rainfed rice fields. The development of rainfed rice fields is very relevant to the increasing national food needs. The goal of this paper is to examine the management of rainfed lowland rice fields to increase the national rice production. Some of the limiting factors are the unpredictable rainwater availability and low soil fertility due to low C-organic and N-total content. Harvesting failures could be caused by water stress at the beginning of the planting stage in the rainy season or just before harvesting in the second season. This could be prevented by planting upland scaffolding in the first planting season, and the kidnap system in the second growing season. The application of soil enhancers is intended to increase soil fertility before fertilizer application, such as straw compost, manure, biochar and agricultural lime or dolomite especially for acidic soils. Balanced fertilization technology that can be applied to rainfed lowland rice fields are Urea 250-300 kg ha<sup>-1</sup>, SP-36 50-75 kg ha<sup>-1</sup>, and KCl 50 kg ha<sup>-1</sup>, providing organic material at least 2 t ha<sup>-1</sup>, and the return of the remaining crop straw to the ground. Balanced fertilization can increase rice yield from 1.8-3.5 t ha<sup>-1</sup> to 5.0-5.8 t ha<sup>-1</sup>.</p>
Intensive vegetable production systems throughout South East Asia are characterised by large nutrient inputs and low nitrogen (N) use efficiencies. In Indonesia, intensive vegetable production is concentrated on volcanic highland soils starting from an altitude of around 700 m above sea level. We measured potential N mineralisation from soil organic matter and from several representative organic materials in Andisols and Inceptisols with andic properties from Central Java, Indonesia. Unamended soils and soils amended with crop residues, animal manures, and compost were incubated during 3-4 months at 25 degrees C in the laboratory, then we monitored N mineralisation. Relative N mineralisation was significantly smaller in the Andisols (average 3.6 +/- 1.0%) than the Inceptisols (7.4 +/- 2.9%), and was negatively related to oxalate-extractable aluminium (Al-ox) (r = -0.749) and soil organic carbon (r = -0.705). This is probably due to the strong protection of organic matter (and organic N) by binding to active Al compounds. Net N mineralisation from the added organic materials was highly variable (ranging from 68.1% for the broccoli residues to 2.6% for tithonia compost), and was best related to the organic N content (r = 0.476). There were no significant correlations between net N mineralisation and biochemical fractions, which we attribute to the large variety of materials used in this study compared with previous studies. The data generated here on N mineralisation potential from soil organic matter, and from a variety of plant materials and animal manures that are commonly used in these intensive vegetable rotations, will allow for the rapid and efficient introduction of N fertiliser advice systems based on balance sheets
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.
The soil cation ratio is the result of the interaction of various factors, including soil acidity, organic C content, clay minerals, and cultivation management. This paper aims were to study the cation ratio in lowland rice in Java and its relationship with the other nutrients. Soil chemical data were collected from survey for soil maps, soil nutrient status maps, and previously published data. The results showed that the average of cation saturation ratio in lowland rice in Java was 70.8:24.5:1.5 for Ca:Mg:K. The Ca, Mg, K, and Na nutrient contents vary by provinces, and there is a high content of Ca, especially in those soils derived from the calcareous parent materials. This high Ca of >50.0 cmol(+) kg−1 has noticed in Grobogan, Bojonegoro, and Gunung Kidul regencies. The domination of Ca cations in the soil can be seen when the Ca saturation >70%, spreading in 36 districts. Ca saturation is positively correlated with pH, P-Bray, and CEC, and negatively correlated with organic C, N-total, Mg, K, and Na saturation. Based on the regression there is a significant negative relationship between Ca and Mg saturations with R2 = 0.92 and a weak negative relationship between K and Na saturations.
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