Syuhada et al. Biochar as soil amendment to a sandy Podzol. A study was conducted toinvestigate the impact of biochar amendment on chemical properties and corn nutrient uptake in a sandy Podzol soil. Four rates of biochar (0, 5, 10, and 15 g kg -1 ) and two rates of inorganic fertilizer (0, and local recommendation rate for corn) were randomly applied to a completely randomized design with four replicates. Corn was grown for 45 days in a glasshouse using sandy Podzol. The increase in pH of the soil was concomitant with decrease of exchangeable Al. The fertilized soil significantly increased total N with concomitant decrease in soil pH due to N nitrification. Positive changes did occur in the soil due to biochar application, leading to significant increase in dry matter yield and corn height. Corn N and K uptakes were significantly increased by the addition of biochar, but the same was not true for Ca and Mg. However, it was found that concentration of N, Ca and Mg in the corn tissue was still lower than their critical level. Our results demonstrate that application of biochar alone is not able to supply enough nutrients for the healthy growth of corn.

Nitrous oxide (N20) contributes to global climate change and agricultural soils seem to be the major source. Lack of information led to this study on the influence of different amounts and sources of nitrogen on N2O emission from a maize (Zea mays L.)-groundnut (Arachis hypogae L.) crop rotation in an Ultisol of the humid tropics. The treatments were: inorganic N + crop residues (NC), inorganic N only (RN), and half of inorganic N + crop residues + chicken manure (NCM). The corresponding amount of N applied was 322, 180, and 400 kg ha(-1) yr(-1), respectively. The N2O emissions depended on the amounts and types of N. A maximum peak (9,889 +/- 2,106 microg N2O-N m(-2) d(-1)) was detected at 2 wk before maize sowing amended with chicken manure, showing a persistent influence on N transformations and N2O release. The mineral N from either applied source became low by 2 to 4 wk, coinciding with the small N2O fluxes or its consumption to a few isolated instances. The N2O flux significantly correlated with the mineral N and water-filled pore spaces. The direct annual N2O emission was 3.94 +/- 0.23, 1.90 +/- 0.08, and 1.41 +/- 0.07 kg N2O-N ha(-1) from the NCM, NC, and RN treatments, respectively. The corresponding N2O-N loss of the applied N plus N fixed by groundnut was 0.83, 0.49, and 0.59%. Overestimations of direct annual N2O emission using the Intergovernmental Panel on Climate Change (IPCC) methodology suggest a location-specific emission factor for variable N sources to be considered.

The use of composted oil palm wastes in the oil palm nursery as an organic component of growing medium for oil palm seedlings seems promising in sustainable oil palm seedling production. This study was conducted to investigate the effects of six oil palm waste compost rates (0, 20, 40, 60, 80, and 100%) on the growth performance of oil palm seedling and nutrient uptake in the prenursery stage (0–3 months). The addition of oil palm compost reduced the soil bulk density (1.32 to 0.53 g cm−3) and increased soil pH (4.7 to 5.1) of growth media. Oil palm waste compost treatment produced positive growth performance up to 70%. A regression analysis indicated in 72% of compost and topsoil mixture as a polybag growth medium was optimum in producing best growth performance of oil palm seedling in the prenursery stage. Foliar analysis implied highest nutrients uptake (N, P, K, Mg, Ca, Fe, Zn, and Cu) for seedlings grown in 60 to 100% compost media.

Recycling of crop residues is essential to integrated and sustainable agricultural management system. Thus, it is of crucial importance to study the decomposition of these residues particularly in the humid-tropics. A litterbag experiment was carried out on an acid soil of the humid tropics of Malaysia. Haulm from groundnut and stover from were placed inside nylon 2 mm mesh bags (20 cm £ 20 cm) and placed on the soil surface in the field with a groundnut -maize rotation system. A total of 21 bags for maize and an equal number for groundnut residues were placed in a field plot. Three bags of each residue type were retrieved at 1, 3, 5, 7, 9, 11 and 13 weeks of decomposition. The decomposed tissue was analyzed for remaining dry matter weight (DMW), nitrogen (N), carbon (C), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) contents. Dry matter 609 ORDER REPRINTS disappearance rate constant (0.158% week 21 ) from groundnut haulm was significantly ðP ¼ 0:01Þ faster than that from maize stover (0.099% week 21 ). A 50% loss of residue N was found after 2 weeks for maize residues and only 1.5 weeks for groundnut residues. Generally, nutrient loss from both residues was in the order of K $ P ¼ N ¼ Mg $ Ca. The results indicated that sowing time of subsequent crop after residue application is crucial to synchronize nutrient release with plant uptake.

Rice plants have been reported to affect methane (CH4) emission from rice fields. The objectives of this study were to determine the effect of rice cultivars on CH4 emission from flooded rice and to develop crop management strategies with low emitting rice cultivars while sustaining high yield. The four rice cultivars studied were Memberamo, Cisadane, IR64, and Way Apoburu. The CH4 emissions were determined in the wet season of 2001/2002 (November-February) using an automated closed chamber technique in an irrigated field condition. Farmyard manure at the rate of 5 t ha-1 was given to the plots to ensure carbon was not limited. Root weight, root length, biomass, and number of tillers were determined at 17, 36, and 57 days after transplanting (DAT). The results showed that the mean CH4 emission was highest in the plot planted with Cisadane (94.8 kg CH4 ha-1), and the lowest with IR64 (37.7 kg CH4 ha-1). The plots treated with emberamo and Way Apoburu resulted an intermediate CH4 emission at the average of 61.1 and 58.9 kg CH4 ha-1, respectively. There was no significant difference in yield between the cultivars tested. The yield of Memberamo, Cisadane, IR64, and Way Apoburu were 5.882, 5.764, 5.873 and 6.065 t ha-1, respectively. Statistical analysis showed that there were no significant differences in the root weight and root length among cultivars. However, Cisadane gave the highest dry matter weight (222 g hill-1) at 57 DAT compared to the other cultivars (175-190 g hill-1). Plant tillers did not show significant differences between the cultivars. Regression analysis showed that CH4 flux was significantly related with root weight, root length, aboveground biomass, and number of plant tillers. This finding shows that the use of selected cultivars, such as IR64, can potentially lower CH4 emission without scarifying yield.

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Low soil organic matter (OM) characterizes most soils of the humid tropics because crop residues are not returned to the field. A two-year (1997)(1998)(1999) field experiment was carried out in an Ultisol to determine the contribution of crop residue application in sustaining yields of maize (Zea mays L.) and groundnut (Arachis hypogaea) in a crop rotation system. Three management practices were compared, inorganic fertilizer with crop residues (T1), inorganic fertilizer without crop residue (T2) and half dose of inorganic fertilizer with crop residues combined with chicken manure (CM) (T3), in a randomized block design. During five crops cycle 1841 of continuous application of crop residues with inorganic fertilizers or combined with CM, 43% of the observed maximum yield of the maize was sustained compared to 21% in plots where crop residues were removed. Nitrogen (N) and potassium (K) uptake by the subsequent crops were significantly higher in crop residue treatments whereas phosphorus (P), calcium (Ca), and magnesium (Mg) were not significantly affected by application of crop residues. In the highly weathered soils of the tropics, incorporation of crop residues appeared to be a beneficial management practice for sustaining crop yields.

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