Plant and Soil Science

Indonesia possesses a rich biodiversity with abundant natural resources such as tropical rain and peat swamp forests, oil and gas deposits, and fertile soils just to name a few. The state policies on natural resource management were decentralized and the power and local autonomy rights were given to provincial and district governments. This resulted in an enormous expansion of oil palm plantations across the country especially over the last three decades. On the one hand it boosted the country's economy by bringing foreign money reserves, but on the other hand has led to severe deforestation, shifting cultivation, peat swamp forests conversion and land degradation. Thus, due to the severity of these environmental consequences and associated climate change implications, oil palm development has received significant attention from all stakeholders and is the subject of global debate. This paper aims to discuss the results of various studies regarding emissions of GHGs from oil palm plantations in Indonesia and highlights the fundamental methodologies Rehman et al.; IJPSS, 4(1): 1-17, 2015; Article no. IJPSS.2015.001 2 followed in assessing GHGs emissions. We found throughout contradictions in the reported rates of oil palm encroachment over peatland and GHG emissions. The former because of diverse methodologies followed in each study i.e. different amounts of time spent in the field, scales of study area, analytical techniques in GIS (data sets and supplementary remote sensing); and the later because of both differences in instrumentation and underlying principles; such as indirect GHG assessments from subsurface drainage(level of water table), subsidence, soil and biomass carbon stock differences, autotrophic and heterotrophic respiration, close chamber methods, eddy covariance techniques and utilization of micrometeorological stations. Finally, the review concludes that almost all studies demonstrate a linear increase in oil palm plantations and proclaim a net negative climate change impact due to conversion from peat swamp forests to oil palm plantations. Therefore, it is being suggested that the pre-existing GHG inventories data should be further worked out to developa 'standard carbon sequestration model for peatlands', supported by updated countrywide peatlands mapping and policy reforms which should address both economic development from the oil palm sector and consider mitigation of GHG emissions from peatlands conversion.

The present study aims to assess the biodiversity of arbuscular mycorrhizal fungi (AMF) associated with cashew (Anacardium occidentale L.) cultivars characteristics in Benin (West Africa). 108 soil samples were collected at 0-20, 20-40 and 40-60 cm depth under cashew trees at Glazoué in the centre Benin. Cashew's cultivars characteristics regarding nut and apple size, apple colors and classes of Diameter at Breast Height (DBH) were the treatments. Soil chemical properties, AMF spores' density and the diversity of AMF in the soil were assessed. Plantation of cashew improved the stock of soil organic carbon (11.24±0.63 and 10.93±0.71 g/kg for 0-20 cm soil depth respectively for cultivars producing big nuts and big apples and cultivars producing small nuts and small apples) and total nitrogen content (1.29±0.11 and 1.21±0.12 g/kg for 0-20 cm soil depth respectively for cultivars producing big nuts and big apples and cultivars producing small nuts and small apples) but it depletes available phosphorus (36.86±6.53 and 41.42±9.22 mg/kg for 0-20 cm soil depth respectively for cultivars producing big nuts and big apples and cultivars producing small nuts and small apples) and exchangeable potassium (0.93±0.10 and 0.79±0.04 cmol/kg for 0-20 cm soil depth respectively for cultivars producing big nuts and big apples and cultivars producing small nuts and small apples). Seven species of AMF (Scutelospora gregarine, Acaulospora colossica, Acaulospora lacunosa, Enthrophospora infrequens, Glomus hoi, Glomus geosporum and Glomus sp.) were identified. They belong to three families and four genera. The species belonging to Glomeracea family were dominants (91.8%) against 5.5% and 2.7% respectively for the Gigasporaceae and Acaulosporaceae. In general, the average numbers of AMF spores were 5.63±0.26; 3.54±0.19 and 1.94±0.15 per gramme of dry soil respectively for 0-20, 20-40 and 40-60 cm depth. The community of AMF was fairly diversified in the soil under cashew's trees. There was an equitable distribution of AMF genera associated with cashew's cultivars characteristics tree.

Amending soil with animal wastes can be useful in food production as well as a means of waste disposal. It has been found to enhance physico-chemical properties and enhance yield. Poultry manure (PM), swine waste (SW), cow dung (CD), and sewage sludge (SS) were added to a hydromorphic ultisol (sandy loam, typic haplusult at the rate of 10 tha-1 (12 kgplot-1)). Maize hybrid (Oba super II) was used as test crop. Randomized Complete Block Design (RCBD) with four replications was used in laying the experiment. Data collected were analyzed using analysis of variance (ANOVA) and means were separated using Fishers' Least Significant Difference (F-LSD). Physical properties of soil influenced by animal wastes include bulk density, total porosity, hydraulic conductivity, gravimetric moisture contents, aggregate stability, and rheological characteristics. Amendments also enhanced soil organic matter, total nitrogen, available phosphorus, potassium, calcium, magnesium and sodium, pH, exchangeable acidity, cation exchange capacity, and base saturation were all higher relative to the unamended plots. Productivity studies revealed that maize growth was significantly affected by amendments especially PM. This was observed in height, leaf area index and yield higher relative to the control. Generally, the increase followed the order PM>SW>SS>CD. Animal wastes especially from poultry sources are recommended for soil amelioration and for increased crop yield in the area.

The objective of this work was to study the interactive effect of biochar and plant growth-promoting endophytic bacteria containing 1-aminocyclopropane-1-carboxylate deaminase and exopolysaccharide activity on mitigating salinity stress in maize (Zea mays L.). The plants were grown in a greenhouse under controlled conditions, and were subjected to separate or combined treatments of biochar (0% and 5%, w/w) and two endophytic bacterial strains (Burkholderia phytofirmans (PsJN) and Enterobacter sp. (FD17)) and salinity stress. The results indicated that salinity significantly decreased the growth of maize, whereas both biochar and inoculation mitigated the negative effects of salinity on maize performance either by decreasing the xylem Na + concentration ([Na + ] xylem ) uptake or by maintaining nutrient balance within the plant, especially when the two treatments were applied in combination. Moreover, in biochar-amended saline soil, strain FD17 performed significantly better than did PsJN in reducing [Na + ] xylem . Our results suggested that inoculation of plants with endophytic baterial strains along with biochar amendment could be an effective approach for sustaining crop production in salt-affected soils.

Diversity, structure and productivity of above-ground compartment of terrestrial ecosystems have been generally considered as the main drivers of the relationships between diversity and ecosystem functioning. More recently it has been suggested that plant population dynamics may be linked with the development of the below-ground community. The biologically active soil zone where root-root and rootmicrobe communications occur is named "Rhizosphere" where root exudates play active roles in regulating rhizosphere interactions. Root exudation can regulate the soil microbial community, withstand herbivory, facilitate beneficial symbioses, modify the chemical and physical soil properties and inhibit the growth of competing plant species. In this review, we explore the current knowledge assessing the importance of root exudates in plant interactions, in communications between parasitic plants and their hosts and how some soil microbial components could regulate plant species coexistence and change Plant Soil (relationships between plants. This review will be focussed on several well documented biological processes regulating plant-plant communications such as exotic plant species invasions, negative root-root communication (allelopathy) and parasitic plant / host plant interactions and how some soil microbial components can interfere with signal traffic between roots. The reported data show that the overall effect of one plant to another results from multiple interacting mechanisms where soil microbiota can be considered as a key component.

ABSTRAK Tanah jerlus adalah suatu masalah yang telah lama dihadapi oleh pesawah-pesawah di kawasan Kedah dan Perlis. Tanah jerlus dicirikan oleh nilai kekuatan struktur lapisan tanah keras (hardpan) yang rendah. Sebanyak lima plot telah disediakan untuk ujikaji yang terletak di dalam wilayah Lembaga Kemajuan Pertanian Muda (MADA), Alor Senibong, Langgar, Kedah. Kelima plot ini dibahagikan kepada empat plot yang terdapat masalah tanah jerlus (Plot A, Plot B, Plot C dan Plot D) dan satu plot tanah normal/tidak jerlus (Plot E) sebagai kawalan. Objektif kajian adalah untuk mencirikan nilai kekerasan struktur lapisan keras dan ciri fizik tanah jerlus di kawasan kajian. Nilai kekerasan tanah diukur pada kedalaman 0-100 cm dan sampel profil tanih jerlus diambil daripada setiap titik jerlus bagi penentuan ciri fizik tanih. Hasil kajian menunjukkan bahawanilai kekerasan tanah didapati paling rendah pada kedalaman 0-30 cm iaitu Plot C (0.26 MPa), Plot A (0.28 MPa),Plot B (0.31 MPa)danPlot D (0.34 MPa), manakala Plot E tertinggi dengan nilai 0.84 MPa. Peratus kandungan air tanih adalah lebih tinggi pada Plot C (47.22 %) diikuti oleh Plot A (44.16 %), Plot B (42.60 %), Plot D (41.78 %) dan Plot E (28.88 %). Ketumpatan pukal tanih mengikut susunan menurun adalah Plot E (1.036 gcm-3) > Plot D (1.008 gcm-3) > Plot B (1.006gcm-3) > Plot A (1.003gcm-3) > Plot C (1.002gcm-3). Nilai kekerasan tanah dapat dikaitkan dengan peratus kandungan air dan ketumpatan pukal tanih yang merupakan elemen penting dalam proses pemadatan tanah. Nilai purata kekerasan tanah di kawasan kajian berkorelasi positif dengan ketumpatan pukal tanih (n=15, r=0.78) dan berkorelasi negatif dengan kandungan air tanih (n=15, r=-0.77). Tanah jerlus di kawasan kajian dikelaskan dalam kelas sederhana lembut (0.20-0.40 MPa). Kata kunci: Kekuatan Struktur Lapisan Keras (Hardpan), Ciri Fizik Tanah Jerlus PENGENALAN Tanah jerlus umumnya terjadi disebabkan oleh keadaan tanah yang sentiasa terendam air dan penggunaan tanah secara berterusan tanpa tempoh rehat menjadi faktor utama yang menyebabkan tanah tidak boleh kembali mengeras ke tahap normal. Sehingga tahun 2012, pihak Lembaga Kemajuan Pertanian Muda (MADA) telah pun merekodkan sebanyak 8,107 hektar daripada 96,000 hektar tanah sawah di Kedah dan Perlis terjejas teruk akibat daripada masalah tanah jerlus (New Straits Times 2013). Penjenteraan sawah padi merupakan satu faktor penting dalam pengeluaran padi berhasil tinggi secara komersial. Asas penjenteraan adalah kebolehlalulintasan jentera di atas sawah padi. Oleh itu, kekuatan tanah untuk menampung berat jentera adalah sangat penting. Kekerasan tanah atau lapisan keras tanah (hardpan layer) mestilah sekurang-kurangnya 0.40 MPa supaya dapat menampung berat jentera yang bekerja (Azizul 2008). Tanah lembut atau jerlus yang berpunca dari air bertakung, saliran tidak sempurna dan permukaan tanah yang tidak rata menyebabkan kawasan sawah tidak dapat dikeringkan (Yea dan Ahmad 2008). Oleh itu, beberapa langkah penyelesaian yang telah dilakukan oleh pihak MADA ialah dengan pembinaan parit jari, struktur kecil saliran dan jalan ladang, namun masalah tanah jerlus masih berlarutan sehingga kini. Berdasarkan uraian diatas dapat disimpulkan bahawa kekerasan hardpan tanah merupakan elemen penting yang

A comparison was made between a long-term rice–wheat cultivation with fertilizer nitrogen–phosphorus–potassium (NPK) or added organics [farmyard manure (FYM), paddy straw (PS), green manure (GM)] and a permanent fallow on bulk density (BD), saturated hydraulic conductivity (Ksat), available water capacity (AWC), maximum water-holding capacity (MWHC), aggregation, and soil organic carbon (SOC) dynamics on an Inceptisol of humid subtropics of eastern India. Continuous cropping caused a net decrease in SOC content. Undisturbed fallow was comparable to soils with FYM, PS, and GM amendments in structural and hydrophysical properties. Maximum WHC and AWC values were in the order of FYM followed by PS, GM, fallow, NPK, and control. The relative efficacy of the organics for physical buildup was FYM > PS > GM, which increased structural indices. This study represents further steps toward understanding the ecological importance of fallow management and integrated use of balanced fertilizer and organics.

Background. Faba bean is an important starch-based protein crop produced worldwide. Soil acidity and aluminium toxicity are major abiotic stresses affecting its production, so in regions where soil acidity is a problem, there is a gap between the potential and actual productivity of the crop. Hence, we set out to evaluate acidity and aluminium tolerance in a range of faba bean germplasm using solution culture and pot experiments. Methods. A set of 30 accessions was collected from regions where acidity and aluminium are or are not problems. The accessions were grown in solution culture and a subset of 10 was grown first in peat and later in perlite potting media. In solution culture, morphological parameters including taproot length, root regrowth and root tolerance index were measured, and in the pot experiments the key measurements were taproot length, plant biomass, chlorophyll concentration and stomatal conductance. Result. Responses to acidity and aluminium were apparently independent. Accessions Dosha and NC 58 were tolerant to both stress. Kassa and GLA 1103 were tolerant to acidity showing less than 3% reduction in taproot length. Aurora and Messay were tolerant to aluminium. Babylon was sensitive to both, with up to 40% reduction in taproot length from acidity and no detectable recovery from Al 3+ challenge. Discussion. The apparent independence of the responses to acidity and aluminium is in agreement with the previous research findings, suggesting that crop accessions separately adapt to H + and Al 3+ toxicity as a result of the difference in the nature of soil parent materials where the accession originated. Differences in rankings between experiments were minor and attributable to heterogeneity of seed materials and the specific responses of accessions to the rooting media. Use of perlite as a potting medium offers an ideal combination of throughput, inertness of support medium, access to leaves for detection of their stress responses, and harvest of clean roots for evaluation of their growth.