超高产夏玉米养分限制因子及养分吸收积累规律研究

2007年和2008年通过大田试验研究了超高产夏玉米养分限制因子和植株养分吸收积累规律。结果表明:用ASI法推荐的氮、磷、钾平衡施肥产量最高,分别达到12051.2 kg/hm2和13246.3 kg/hm2,施用氮肥平均增产8.92%,钾肥平均增产7.14%,增产效果显著,氮和钾为超高产夏玉米养分主要限制因子。超高产夏玉米植株体内氮、磷、钾的积累量均随生育期的延长而增加,到成熟期达到最大值,养分积累量的大小顺序为氮钾磷,每生产100 kg经济产量吸收养分比例N∶P2O5∶K2O为2.40∶1∶2.73。拔节期至吐丝期是养分吸收的关键时期,养分吸收速率大,积累量高,吐丝后植株仍能吸收较多的氮、磷。从出苗到吐丝期,叶片是氮、磷的分配中心,生育后期茎叶中氮、磷的转运率较高,而钾转移比例较小。超高产夏玉米整个生育期能持续吸收养分,吐丝后适当追肥保证灌浆期养分充足供应对夏玉米超高产至关重要。     

Multiple-nutrient limitation of upland rainfed rice in ferralsols: a greenhouse nutrient-omission trial

Abstract

To optimize the nutrient management of upland rice production on tropical ferralsols, a greenhouse experiment was established using the multi-nutrient omission approach. A reciprocal soil origin-rice cultivar transplant experiment was also conducted to better understand the relative contributions of the soil origin and the rice cultivar in rice nutrient limitation. We tested the deficiency of seven major and secondary nutrients [nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), and silicon (Si)] and a solution of six micronutrients (B, Mn, Cu, Co, Na, Mo) likely to limit the growth of two upland rice cultivars, Chhomrong Dan and Nerica 4, on two Ferralsols from the highlands of Madagascar. We found severe multiple nutrient deficiencies. For both cultivars, P, Ca, N, Mg omission significantly depressed the shoot and root dry biomass and their amounts in plant tissues. However, the main limiting nutrients were not the same in both soils. We conclude that the multinutrient deficiencies observed for rice growth in the Ferralsols are site-specific, even though P limitation appears to be in common, and requires a holistic consideration of the mineral fertility, including micronutrients.     

不同氮磷钾处理对木薯产量、 养分积累、 利用及经济效益的影响

于2010和2011年,以木薯品种华南205（SC205）为试验材料,采用3414方案设计,研究了氮磷钾不同施肥处理对木薯产量、 养分积累利用和经济效益的影响,并通过多元回归建立红壤旱地木薯的施肥效益方程。结果表明,施肥处理的鲜薯产量显著高于不施肥处理; 缺氮处理的鲜薯产量显著低于缺磷和缺钾处理,对鲜薯产量的影响N＞K2O＞P2O5; 施肥处理中以N2P2K2处理的鲜薯产量、 鲜薯淀粉含量、 鲜生物量、 养分收获指数和经济效益最高,而产投比以N2P2K0处理最高,N1P2K1处理其次,N2P2K3处理最小。木薯植株养分积累总量K2O＞N＞P2O5,平均100 kg鲜薯养分需求量分别为1.00、 0.91和0.11 kg,平均养分收获指数分别为0.53、 0.33和0.46。相关分析表明,木薯产量与施氮量呈极显著正相关,与施钾量呈显著正相关,与施磷量相关不显著。在本试验条件下,三元二次方程拟合结果表明,达到经济最佳产量时的氮、 磷、 钾施用量分别为205.37、 65.43和311.30 kg/hm2,产投比为6.23。     

Nitrogen and phosphorus requirements of different wheat plant types under dryland and irrigated conditions 1

The wheat (Triticum aestivum L.) plant type in major producing areas of the U.S. is changing rapidly from tall cultivars to high‐yielding semidwarf cultivars. Objectives of experiments were to determine if nitrogen and phosphorus nutritional requirements differ between traditional tall cultivars and modern semidwarf cultivars under dryland and irrigated conditions. ‘Larned’, a tall cultivar; ‘Newton’, a semidwarf cultivar; and ‘Plainsman V, a high‐protein semidwarf cultivar, were grown with all combinations of three nitrogen fertilizer levels (0, 84, and 168 kg N/ha) and two phosphorus fertilizer levels (0 and 90 kg P₂O₅/ha) at Colby, Kansas for two years. Three levels of irrigation—dryland, limited irrigation, and full irrigation—were applied. Grain yields were highest with 84 kg N/ha under dryland and with 168 kg N/ha under irrigation. Phosphorus increased grain yield under dryland conditions one year, but had no effect under irrigated conditions. Cultivar X nutrition interactions from differential yield responses to fertility levels occurred under the dryland and limited irrigation regimes one year. Grain protein content was increased by nitrogen fertilization under all regimes both years and was decreased only by phosphorus fertilization under dryland conditions one year. Cultivar X nitrogen interactions for grain protein occurred under all irrigation regimes. We concluded that nutrient requirements do not differ between tall and semi dwarf wheat culti‐vars under any irrigation regime. Raising the recommended level of nutrients, particularly nitrogen, should be considered for all cultivars, both tall and semidwarf.     

Response of potatoes to different nutrient solution management in a closed hydroponic system

Ion control of nutrient solutions to control nitrogen (N), phosphorus (P), and potassium (K) was developed for Superior (medium-to-early maturing) and Atlantic (mid-late) potato cultivars grown in closed hydroponic systems in which solutions were replenished and recirculated. Results were compared with conventional nutrient solution management strategies. In the “solution replacement” treatment, nutrient solutions were completely replaced each week. In the “electrical conductivity (EC) control” treatment, water use by potato plants was compensated by adding ground water to achieve the original volume (water replenishment) and the diluted EC of the solution was adjusted to the target levels using stock solution. In “ion control” treatment, ammonium dihydrogen phosphate (NH₄H₂PO₄) and potassium nitrate (KNO₃) were added to the EC-controlled nutrient solution. The amounts increased with plant age in both cultivars. The concentrations of nitrate (NO₃), P, and K in the ion control nutrient solution could be maintained at target levels. In water replenishment, recycling of nutrient solution resulted in a progressive decrease in EC and an increase in pH. Root activity increased by 93% and 59% in the Superior and Atlantic cultivars, respectively, compared with the nutrient solution replacement. These changes decreased photosynthesis, plant growth, water use, and thus tuber growth in the Superior cultivar. Decreased growth of shoots and tubers occurred without affecting photosynthesis in the Atlantic cultivar. Although there were no significant differences in root activity, photosynthesis, or plant growth between the ion control treatment and the EC control treatment, increased tuber growth was observed in the ion control treatment, possibly as a result of the constant supply of nutrients. High tuber growth and the capability to maintain solution nutrient concentration in the ion control treatment are highly desirable for closed hydroponic systems.     

Effects of Elevated Ozone Concentrations on Thai Jasmine Rice Cultivars (Oryza Sativa L.)

This study investigated the effects of O₃ on growth, yields and physiological characteristics of Thai Jasmine rice cultivars. Rice was exposed to O₃ for 7 h day^?1 in a closed chamber for 113 days, beginning from seedling until harvest. O₃ concentration in each chambers was controlled at 0 ppb, 50 ppb, 100 ppb, 150 ppb and at the ambient level. Effects of O₃ on leaf area index (LAI) became obvious at maturity when LAI significantly decreased in the treatments under elevated O₃ concentrations. Results in shoot biomass indicated that shoot length was more affected by O₃ than shoot dry weight. Root length rather than dry weight was significantly reduced in all cultivars. The most severe damage of O₃ was found in photosynthetic components, namely chlorophyll and carotenoid contents, and rate of net photosynthesis. Yield components were also strongly affected by O₃. The highest reduction in filled seed per ear was found in the Pathumthani 1 cultivar by 78% when it was exposed to 150 ppb O₃ compared to the control (0 ppb). Similarly, 100-grain weight was also reduced as much as 12.3% in this cultivar.     

Nutrient Distribution and Stem Length in Flowering Stems of Protea Plants

A study of nutrient distribution in the flowering stem of proteas was carried out in commercial protea plantations of each of the cultivars ‘Scarlett Ribbon’, ‘High Gold’, ‘Veldfire’, and ‘Sunrise’ of Leucospermum cordifolium, and of the species L. patersonii located in a subtropical zone (La Palma Island, Canarian Archipelago). Flowering stems were cut into different parts: flower bud, leaves from half proximal stem to the flower bud, leaves from half distal stem to the flower bud, half proximal stem to the flower bud, and half distal stem to the flower bud. Nutrient content of the different parts of the flowering stems of the cultivar and the species gave significant differences in some cases, depending on the nutrient and the cultivar. Occasional dissimilarities among the levels of nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), sodium (Na), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) were determined in comparisons among half proximal stems and half distal stems, independent of the cultivar. The same trend was observed when nutrient contents of the leaves from the half distal and the half proximal stems were compared. Phosphorus exhibited the lowest concentrations of all macronutrients in the different organs. Flower buds presented the smallest levels of macro-and micronutrients, while the leaves of the half distal and half proximal stems showed the highest values. The influence of nutrients of leaves from the half proximal stems on the stems length varied among cultivars.     

在施钾条件下灌溉水稻的养分吸收和利用效率研究

Potassium is one of the most important nutrients for rice production in many areas of Asia, especially in southeast China where potassium deficiency in soil is a widespread problem. Field experiments were conducted for four consecutive years in Jinhua City, Zhejiang Province, to determine utilization of nutrients (N, P and K) by inbred and hybrid rice and rice grain yields as affected by application of potassium fertilizer under irrigated conditions. Grain yield and nutrient harvest index showed a significant response to the NPK treatment as compared to the NP treatment. This suggested that potassium improved transfer of nitrogen and phosphorus from stems and leaves to panicles in rice plants. N and P use efficiencies of rice were not strongly responsive to potassium, but K use efficiency decreased significantly despite the fact that the amount of total K uptake increased. A significant difference between varieties was also observed with respect to nutrient uptake and use efficiency. Hybrid rice exhibited physiological advantage in N and P uptake and use efficiency over inbred rice. Analysis of annual dynamic change of exchangeable K and non-exchangeable K in the test soil indicated that non-exchangeable K was an important K source for rice. Potassium application caused an annual decrease in the concentration of available K in the soil tested, whereas an increase was observed in non-exchangeable K. It could be concluded that K fertilizer application at the rate of 100 kg ha^-1 per season was not high enough to match K output, and efficient K management for rice must be based on the K input/output balance.     

Macro‐ and micronutrients removed by upland and lowland rice cultivars in West Africa

Abstract

Plant analysis is an important component of soil fertility and plant nutrition research. Plant analysis at harvest of the crop forms the basis for constructing nutrient balances and assessing the nutrient needs of production systems. Amounts of macro‐ and micronutrient elements removed by improved, upland and lowland rice cultivars were determined in field experiments at two sites in Ivory Coast. Amounts of nitrogen (N), zinc (Zn), and manganese (Mn) removed for 11 rice grain yield by upland and lowland rice cultivars were similar, but the amounts of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) removed were higher for lowland than upland rice. The nutrient element harvest indexes (amount in grain/amount in grain plus straw) varied between the cultivars, but more importantly, among nutrient elements. On average the nutrient harvest index was highest for P (69%) and lowest for K (10%). The results suggest that the nutrient requirement of rice for K can be met to a large extent through the recycling of K in rice straw. The amounts of other major nutrients, N and P in the straw were small and hence less scope for supplying these nutrients through the recycling of rice straw.     

浅层施肥对水稻苗期养分吸收及土壤养分分布的影响

采用盆栽土柱试验研究不同施肥深度对水稻秧苗生物量、养分吸收及土壤养分分布的影响,以期为水稻育秧合理施肥提供理论依据。结果表明:播种后10天,各处理水稻生物量无显著差异;播种后20天,施肥深度1 cm处理生物量与其他处理相比平均显著增加80.6%;播种后40天,施肥深度1 cm和5 cm处理与10 cm处理相比分别显著增加70.9%和30.7%。养分吸收结果与生物量表现一致,播种后20天,施肥深度1 cm处理秧苗氮、磷、钾素吸收量分别平均提高86.9%、156.9%和202.7%;播种后40天,施肥深度1 cm和5 cm处理与10 cm处理相比分别增加52.3%和24.8%、23.8%和20.4%、50.5%和43.1%。随着生育进程的推进,土壤有效养分含量均逐渐下降,且有向下迁移的趋势;其中施肥深度1 cm和5 cm处理0~10 cm土层中无机氮、速效磷、速效钾含量显著高于其他处理。适宜的浅层施肥明显促进水稻秧苗的生长发育,浅层施肥方式施入的速效养分主要集中于土壤上层,利于秧苗生长对养分的吸收,提高秧苗养分含量,增加养分吸收量,有利于提高养分资源利用效率。     

Rice straw biochar amended soil improves wheat productivity and accumulated phosphorus in grain

Abstract

Biochar is a pyrolyzed biomass produced under limited oxygen or oxygen absent conditions. Few investigations have been conducted to determine the combined effect of biochar with chemical fertilizer on growth, yield and nutrient distribution pattern in root, shoot and grain in wheat as well as changes in soil physiochemical properties. This research was designed to study the combined effect of chemical fertilizer and rice straw-derived biochar on soil physio-chemical properties, growth, yield and nutrient distribution pattern within wheat plant tissue and grain. Results showed that rice straw biochar caused a significant decrease in soil pH and increase in soil organic matter as well as nutrients like total nitrogen (TN), potassium (K), magnesium (Mg) and boron (B) due to incubation. Result also showed that root biomass and straw did not differ between Bangladesh Agricultural Research Council (BARC) and ½ BARC?+?rice straw biochar treatment. Similarly, thousand grain weight and grain yield did not differ between the same treatments. The phosphorus concentration in wheat grain was highest in ½ BARC?+?rice straw biochar as compared to other treatments. The use of rice straw biochar in addition to the chemical fertilizers in wheat production systems is an economically feasible and practical nutrient management practice. Our findings urged that reduction of chemical fertilizer application is possible with supplementation of rice straw biochar.     

Effect of elevated O3 on rhizospheric enzymatic activities of ozone sensitive and tolerant wheat cultivars

Tropospheric ozone (O₃) is considered harmful to agriculture production and soil community. Wheat cultivars HD 2987 (O₃ sensitive) and Kharchiya 65 (O₃ tolerant) were grown under ambient and elevated (ambient + 30 ppb) levels of O₃ (EO) using open top chambers, and microbial biomass and enzymatic activities were investigated in soil rhizosphere. Elevated O₃ declined soil enzymatic activities related to carbon cycling viz. β-glucosidase, cellobiohydrolase, cellulase and amylase more in sensitive cultivar compared to tolerant. Enzymatic activities linked to nitrogen cycling like N-acetyl-glucosaminidase and urease decreased while protease and glycine aminopeptidase increased. Microbial biomass carbon and nitrogen declined more in sensitive cultivar by 11.1 and 21.2%, respectively. Root biomass reduced in wheat cultivars with an increase of their phenolics contents by 34.3 and 10.2% in HD 2987 and Kharchiya 65, respectively at 60 days after germination. Non-significant changes were observed in soil organic carbon and total nitrogen in both the cultivars. Redundancy analysis suggested that soil enzymatic activities were predominantly affected by O₃ induced changes in microbial biomass carbon and root biomass. Study also showed that rhizosphere of sensitive cultivar HD 2987 was affected more under EO as compared to tolerant Kharchiya 65.     

稻-麦轮作体系不同施肥模式对氮肥利用效率和土壤有效养分平衡的影响

土壤肥力和养分利用效率是保障可持续粮食生产的基础。通过田间试验研究了稻—麦轮作体系下不同施肥模式氮肥利用效率和土壤有效养分的变化,结果表明:在减少养分总投入量的条件下,有机肥部分替代化肥处理(RF-OM和RF-S处理)水稻地上部总生物量显著高于LRF处理(P<0.05),与FP处理差异不大;小麦秸秆生物量与FP和LRF处理差异均不显著,籽粒生物量及地上部总生物量与LRF处理相差不大。水稻收获期RF-OM处理地上部主要器官含氮量与LRF处理差异不显著,氮素积累总量显著高于LRF处理(P<0.05);小麦收获期RF-OM和RF-S处理秸秆、籽粒含氮量和氮素积累量与LRF处理均无显著差异。收获期RF-OM和RF-S处理水稻糙米和稻壳、小麦秸秆和籽粒含磷量及磷素积累量与FP和LRF处理差异都不大;水稻秸秆、稻壳及小麦秸秆含钾量和钾素积累量均显著高于FP和LRF处理(P<0.05)。有机肥部分替代化肥处理水稻、小麦氮肥农学利用率、氮肥表观回收率和氮肥偏生产力与FP和LRF处理相比均显著提高(P<0.05),氮素籽粒生产效率也高于FP和LRF处理,甚至达到显著水平(P<0.05)。试验表明,水稻、小麦收获期增钾处理(RF-OM和RF-S处理)土壤速效钾、缓效钾含量显著高于FP和LRF处理(P<0.05),水稻收获期土壤碱解氮和小麦收获期土壤有效磷含量与LRF处理差异不大,同时,经1个稻—麦轮作周期后,4个施肥处理土壤有效养分(碱解氮、有效磷、速效钾、缓效钾)含量均高于供试土壤。有机肥部分替代化肥能显著提高稻麦氮肥利用效率,有利于土壤有效养分平衡,并显著提高土壤速效钾和缓效钾养分含量,是适宜的稻麦化肥减量和稳产增效施用技术。     

Effect of Two Nitrogen Forms on the Growth and Iron Nutrition of Pea Cultivated in Presence of Bicarbonate

ABSTRACT

Two cultivars of pea: ‘PS210713’ (‘PS’), sensitive to iron deficiency, and ‘Marveille de Kelvedon’ (‘MK’), tolerant, were cultivated in controlled climatic conditions during one month, on a nutrient solution containing either nitrate (NO₃ ^?, 4 mM) or ammonium (NH₄ ⁺, 4 mM) and in the presence of bicarbonate (10 mM). The effects of these nitrogen forms on the growth and the mineral nutrition, and especially iron nutrition are analyzed.

The reduction of growth by bicarbonate was approximately 30% in case of NO₃ ^? nutrition in the two cultivars, whereas in ammoniacal treatment the reduction is only 6% and 18% respectively in ‘PS’ and ‘MK’ cultivars.

In presence of bicarbonate, the plant growth is not stimulated by NO₃ ^?relatively to its growth on ammoniacal medium, as often noticed when plants are cultivated on medium without bicarbonate: In presence of this compound, the biomass production of plant pea, was not influenced by the nitrogen forms. The nitric source led to a ferric chlorosis in the sensitive cultivar plants whereas any chlorosis was noted when ammoniacal source was applied. On the other hand, nitric nitrogen form decreased the nitrogen feeding of plants and increased the potassium one, while the effect of the ammoniacal nitrogen form on these nutrients was quite the inverse. In addition, the later increased the allocation of iron towards shoots. Besides, with this nitrogen source there was not accumulation of nitrate in the plant tissues. In nitric feeding case, the nitrate is mainly accumulated in the roots of the two cultivars. It is noticeable that the sensitive cultivar (‘PS’) accumulates three times more nitrate than the tolerant one (‘MK’).

On the level of the whole plant, the iron and phosphorus nutrition seems unaltered by the nitrogen form.     

Factors determining soil nutrient distribution in a small-scaled watershed in the purple soil region of Sichuan Province, China

Determining soil nutrient distribution is critical to identify sites which are at risk of N and P loading. Equally important are determining factors that influence such distribution (e.g. land use, land management, topography, etc.). In this research, soil nutrient distribution and its influencing factors were studied in a small-scaled watershed in the purple soil region of Sichuan Province, China. The watershed is 1.3 km² with a complex land management system including agriculture and forestry. Surface soil samples (0–20 cm) from 48 sites within the watershed were collected in the spring of 1999 and analysed for chemical properties. When spatial distribution patterns of soil organic matter and soil nutrients were considered, several patterns were evident. Soil organic matter and total nitrogen coincided with high soil nutrients in the center of the watershed. Total phosphorus was linked to low soil nutrient contents on hilltops, while total potassium was characterized by low variability and high soil nutrient content throughout the watershed. Water-soluble nutrients in soils were highly variable throughout the watershed. Results of this study indicate that land use, topography and other variables play important roles in controlling the spatial distribution of most soil nutrients. However, the relative roles of these indices were nutrient specific. The relationship was therefore complex. Land use, silt, and sand content contributed to a high level of heterogeneity for soil organic matter and total nitrogen with the former being the dominant factor. Land use, particle size distribution (silt and sand) and topographic factors (slope and elevation) contributed to the variability of total phosphorus. However, particle size distribution and topographic factors were the dominant factors affecting total phosphorus. Elevation influenced the concentration of total potassium and land use controlled the concentration of dissolved phosphorous. No significant relationship was found between the studied characteristics and nitrate nitrogen.     

不同绿肥对土壤肥力及后茬水稻养分吸收的影响

为了探究不同绿肥品种之间的生长差异及其翻压后对后茬水稻养分的影响，通过选取7种不同绿肥（紫云英、白三叶草、金花菜、光叶苕子、箭筈豌豆、油菜、二月兰），以冬闲田（CK）为对照，进行大田试验，分析不同绿肥品种的生长性状、土壤肥力和水稻的产量、养分、养分累积量等指标。结果表明：不同的绿肥作物品种存在着不同的生长差异，综合来看以光叶苕子、箭筈豌豆的生物量最高，分别为46.07 t/hm2、38.74t/hm2，二者养分含量及养分累积量显著高于其他绿肥品种，适合作为苏北地区种植的绿肥品种；种植绿肥具有提高土壤肥力的潜力，促进土壤养分累积，同时对改良土壤肥力具有积极的作用。箭筈豌豆翻压后的土壤pH比CK 高出0.71%，光叶苕子翻压后有机质含量、全氮含量比CK高出1.56%、8.86%；绿肥翻压后对水稻秸秆和籽粒的氮、磷、钾含量及其累积量有了显著的增加，其中以箭筈豌豆的综合效果最好，与CK相比，箭筈豌豆翻压后水稻秸秆全氮累积量、全磷累积量分别提高15.18%、14.98%，水稻籽粒全氮累积量、全钾累积量分别提高9.98%、15.02%，水稻地上部全氮总累积量、全磷总累积量分别提高14.75%、20.42%。综上，光叶苕子、箭筈豌豆的生物量、养分累积量较高，推荐作为该地区种植的绿肥品种；光叶苕子能够对土壤肥力有一定的提高，箭筈豌豆能够促进水稻养分含量及养分累积量。研究结果可为苏北地区绿肥的利用与推广提供理论依据。     

基于养分专家系统的侧深施肥技术对宁夏引黄灌区

为了寻求合理施用肥料与改善水稻养分利用的有效措施,通过2016—2018年在宁夏引黄灌区开展的8组田间试验,研究基于养分专家系统的侧深施肥技术（NE-SD）对水稻产量与养分利用率的影响。结果表明：与农民习惯施肥（FP）处理相比,养分专家系统（NE）处理在减氮24.85%、减磷24.78%、增钾90.71%的基础上,稻谷增产4.71%;氮素、磷素、钾素累积量分别增加2.24%,4.40%,15.09%;氮肥、磷肥、钾肥利用率分别增加9.84,8.78,1.99个百分点;氮肥、磷肥、钾肥农学效率分别增加4.73,7.69,1.54 kg/kg。基于养分专家系统的侧深施肥技术,能够深化4R养分管理方法,表现出较好的应用效果。与FP处理相比,NE-SD处理稻谷增产7.53%;氮素、磷素、钾素累积量分别增加3.92%,7.87%,18.74%;氮肥、磷肥、钾肥利用率分别增加11.09,11.32,5.82个百分点;氮肥、磷肥、钾肥农学效率分别增加5.87,11.31,3.54 kg/kg。因此,在宁夏引黄灌区,NE推荐施肥与NE推荐施肥的基础上,采用侧深施肥技术 2种施肥方法均能在减少肥料投入的基础上,增加稻谷产量,增加水稻养分累积量,提高养分利用率,降低土壤氮素、磷素盈余。     

Nutrient Removal,Fertilization Needs and Yields of Protea Plants Cultivated in Subtropical Conditions

A study of nutrient removal was carried out in commercial protea plantations of each of the cultivars ‘Scarlett Ribbon,’ ‘High Gold,’ ‘Veldfire,’ and ‘Sunrise’ of Leucospermum cordifolium, and of the species L. patersonii,located in a subtropical region (La Palma, Canarian Archipelago).

Flowering stems of optimal commercial quality were taken from each of the mentioned cultivars and species, once a year (2003 and 2004) at harvest time (January to April), and the different organs were analyzed separately. Flowering stems of the cultivars ‘High Gold’ and ‘Veldfire’ presented the highest contents of most studied nutrients, whereas the opposite was observed in ‘Scarlett Ribbon’ and L. patersonii. Mean yields of flowering stems varied very much among cultivars, and the highest ones were those of ‘High Gold’ and ‘Scarlett Ribbon’. The cultivar ‘High Gold’ removed the highest quantities of studied nutrients, and the contrary was observed in L. patersonii for most of them.

Suitable rates of nitrogen (N): phosphorus (P): potassium (K) fertilizers for nutrient restitution purposes were 1:0.08:0.40 for ‘Scarlett Ribbon,’ 1:0.08:0.66 for ‘High Gold,’ 1:0.08:0.38 for ‘Veldfire,’ 1:0.09:0.75 for L. patersonii;and 1:0.18:1.11 for ‘Sunrise’.     

Amending Chemical Fertilizers with Rice Straw Compost and Clinoptilolite Zeolite and Their Effects on Nitrogen Use Efficiency and Fresh Cob Yield of Zea mays L.

A field study was carried out from April 2014 to August 2014 for two consecutive planting cycles of Zea mays L. on Nyalau Series (Typic Tualemkuts) to determine the short-term effects of co-application of chemical fertilizers, rice straw compost, and clinoptilolite zeolite on (i) ammonium adsorption and desorption, (ii) nitrogen, phosphorus, and potassium uptake and use efficiency, and (iii) yield of Zea mays L. (cobs). Amending urea with rice straw compost and clinoptilolite zeolite improved nitrogen use efficiency because of temporary adsorption and desorption of ammonium on the exchange sites of compost and clinoptilolite zeolite. Combined use of chemical fertilizers, rice straw compost, and clinoptilolite zeolite enhanced uptake of nitrogen, phosphorus, potassium, calcium, and magnesium. Co-application of chemical fertilizers, rice straw compost, and clinoptilolite zeolite can improve the availability of soil nutrients. This approach can also improve nutrient use efficiency and yield of Zea mays L.     

Study on the improvement of fertilizer dressing and soil management in the rice field

Major part of nitrogen and phosphorus in the harvested rice plants was proved to be derived from soil nutrients by our field tracer experiments using 15-N and 32-P, even under heavy dressing of ammonium sulfate and superphosphate of over 75 kg per hectare in terms of N and P₂O₅ respectively. It fits quite nicely to Japanese farmer's common understanding, that the upland crops grow on the basis of fertilizer, and paddy rice on soil fertility. The Japanese rice soils, particularly under waterlogged conditions in summer, liberate rich nutrients from the organic matter, and the fertility of soils presents continuous supply of nitrogen and phosphorus throughout the rice Plant life.