干旱胁迫下钾素对甘薯碳水化合物及内源激素含量的影响

【目的】研究干旱胁迫下施钾量对不同生长时期甘薯碳水化合物及内源激素含量的影响,为甘薯的抗旱高产栽培提供理论依据。【方法】选用食用型甘薯品种‘泰中6号’为材料,以硫酸钾（K₂SO₄）为供试肥料,水分处理设土壤最大持水量的60%～70%和30%～40%,依次代表正常供水（W1）和干旱胁迫（W0）;钾肥设K0、K1、K2、K3四个水平,K₂O用量分别为0、120、240和360 kg/hm2。分析了不同生长时期甘薯干物质含量、淀粉和可溶性糖含量、内源激素含量及收获期块根产量。【结果】干旱胁迫下甘薯植株干物质含量、块根和淀粉产量显著降低,施钾有利于甘薯植株干物质含量的提高、块根的膨大和淀粉的生成和积累,甘薯植株和块根干物质含量、块根淀粉含量和积累量最大均为K2处理,较K0提高幅度最大分别达到31.7%、43.6%、10.6%和50.6%。相同钾用量条件下,干旱胁迫下块根单薯重显著高于正常灌水,单株结薯数显著低于正常灌水。正常灌水条件下施钾后甘薯叶片可溶性糖含量降低,而块根可溶性糖含量升高,干旱胁迫下施钾使甘薯叶片和块根可溶性糖含量增大,较K0提高幅度最高分别达到31.4%和36.0%。干旱胁迫下施钾后甘薯叶片和块根IAA、ABA、ZR和GA含量显著增大,较K0提高幅度最高分别达到12.7%、15.7%、12.0%、10.4%和21.4%、15.6%、65.7%、13.0%,促进了甘薯植株碳水化合物含量和干重的提高,块根淀粉积累速率增大。【结论】干旱胁迫下施钾促进了干物质向块根的分配,提高了甘薯块根单薯重,从而增加了单位面积甘薯块根产量。干旱胁迫下钾素提高甘薯块根和叶片内源激素（ABA、IAA、ZR、GA）含量,块根内源激素含量的增加促进了块根淀粉的合成和积累,叶片内源激素含量的增加促进了地上部茎叶生长、茎叶干物质积累和叶片可溶性糖含量的增加,增强了甘薯的抗旱性。     

施氮量对木薯养分吸收和土壤有效养分平衡的影响

从高效施肥角度出发,采用田间试验,研究施氮量对木薯干物质积累、养分吸收及土壤有效养分含量的影响。结果表明:随施氮量的增加,茎、叶干物质积累量显著增加,但块根干物质积累量先增后降,以施氮130 kg/hm~2的最高,比不施氮增加18.13%。增加施氮量,木薯各器官磷、钾积累量及茎、叶氮积累量明显增加,块根氮积累量则先增加后下降。氮肥农学利用率、生理利用率及偏生产力随施氮量的增加而显著下降,氮肥吸收利用率以施氮130 kg/hm~2的最高,比其他处理提高11.37%~25.12%。木薯收获后,随施氮量的增加,土壤碱解氮明显增加,有效磷及速效钾不同程度下降,但各处理有效磷、速效钾及施氮195 kg/hm~2处理的有效氮明显盈余。综合分析认为,本研究条件下木薯施氮130 kg/hm~2较为适宜。     

施钾对木薯产量及钾养分吸收的影响

为探索施钾对木薯生长发育、钾含量、钾积累量及钾肥利用效率的影响,采用田间试验,以我国主栽品种SC205为材料,设K_2O用量0、120、240 kg/hm~2共3个水平,于不同生育期测定木薯叶片、茎秆、细根、块根的干物质量、钾含量,并在木薯收获期调查、测定农艺性状及块根鲜薯产量(FRY)。结果表明:(1)与不施钾相比,施钾显著提高木薯株高、叶面积、叶面积指数、叶绿素含量及鲜薯产量,增幅分别为16.1%~19.0%、3.8%~8.4%、12.8%~18.2%、13.6%~17.3%、12.8%~29.4%、9.9%~25.6%,其中,K_(120)处理产量最高,达27.1 t/hm~2;(2)施钾显著提高各组织钾含量及钾积累量,K_(120)和K_(240)处理间的钾积累量无显著差异;不同组织钾含量表现为叶片茎秆细根块根;随生育期推进,钾素积累的主要组织由叶片向茎秆和块根转变;(3)木薯钾肥效率、钾素生理效率、钾素利用效率、钾素收获指数均随施钾量增加而显著降低,100 kg鲜薯需钾量随施钾量增加显著提高。综合木薯产量、钾积累量、钾肥利用效率等指标综合分析,建议木薯施钾量为120 kg/hm~2。     

钾素对食用型甘薯糖代谢相关酶活性的影响

为了探讨钾素提高甘薯块根可溶性糖含量的生理基础。选用典型的食用型甘薯品种北京553,设置不同施钾处理,于2009～2010年2个生长季在山东农业大学农学试验站进行试验。采用甘薯块根膨大过程中定期取样的方法,测定块根可溶性糖和淀粉含量及相关酶活性、功能叶蔗糖含量及相关酶活性。结果表明,与对照比较,施用钾肥能显著提高块根产量、可溶性糖及各糖组分含量,其中K2O用量为24 g/m2处理增幅最大,为最适用量。进一步研究发现,适宜供钾处理显著提高了功能叶磷酸蔗糖合成酶活性和蔗糖含量,生育期内平均增幅分别为10.31%和34.13%,同时提高了块根中蔗糖合成酶、不溶性酸性转化酶的活性,生育期内平均增幅为16.47%和3.66%,在提高源端光合产物供应的同时促进蔗糖在库端的卸载,促进块根中淀粉和可溶性糖的积累;适宜供钾处理还提高了块根中-和-淀粉酶的活性,生育期内平均增幅分别为26.06%和14.64%,促进淀粉向可溶性糖转化。此外,适宜供钾处理还显著提高了生长前期和后期块根中可溶性酸性转化酶活性、以及生长后期块根中蔗糖-蔗糖果糖基转移酶活性,促进了葡萄糖、果糖和果聚糖在块根中的积累。在甘薯收获期,块根可溶性糖和淀粉含量分别提高了13.52%和3.02%。即钾肥能够增加块根中蔗糖的供应量、促进块根对蔗糖的吸收、促进淀粉水解,是其提高块根可溶性糖含量的生理原因。     

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。     

摘叶对不同株型木薯品种产量和氮磷钾素积累分配的影响

  【目的】  叶片是作物进行光合作用的重要器官,与物质生产、养分吸收和产量形成有密切关系。研究留叶数对木薯养分积累和产量的影响,以期为木薯高产栽培和氮磷钾养分高效利用提供理论依据。  【方法】  采用裂区设计,以株型、品种、留叶数分别为主区、裂区和再裂区。试验以紧凑型品种‘华南205’(SC205)、‘桂热4号’(GR4)和伞型品种‘华南12号’(SC12)、‘华南15号’(SC15)为材料,设计12个留叶数处理(9、18、27、36、45、54、63、72、81、90、99和108片),分析了单株摘叶及成熟期单株的氮、磷、钾素积累量。  【结果】  随留叶数增多,单株摘叶的氮、磷、钾素积累量随之下降,单株鲜薯产量随之显著增加,成熟期全株和全生育期植株的氮、磷、钾素积累量随之呈显著增加或呈“单峰”或“双峰”趋势。不同品种不同元素的积累规律有差异。紧凑型品种单株摘叶的氮素积累量较伞型品种降低了4.56%,而磷、钾素积累量较伞型品种分别提高了10.23%、10.00%。紧凑型品种成熟期全株的氮、磷、钾素积累量较伞型品种分别提高了31.00%、42.48%和50.92%。在成熟期,留叶数增多,在块根和叶片中的氮、磷、钾素分配率随之提高,而在茎秆中的氮、磷、钾素分配率随之下降,氮、磷、钾素收获指数随之呈增加或“单峰”或“双峰”趋势。紧凑型品种氮、磷、钾素收获指数高于伞型品种,两株型分别为0.48、0.63、0.58和0.42、0.60、0.55。随着留叶数增多,成熟期全株的氮、磷、钾素分配率随之提高,而单株摘叶的氮、磷、钾素分配率随之下降。紧凑型品种在成熟期全株中的氮、磷、钾素分配率较伞型品种分别提高了7.33、5.45和4.36个百分点。  【结论】  木薯留叶数越多,摘叶的数量和干物质量越少。随着留叶数增加,木薯产量随之增加,成熟期全株的养分积累量和块根、叶片的养分分配率随之提高。木薯摘叶后,叶片光合产物优先满足地上部生长。在本试验条件下,块根膨大期适宜的留叶数为81～90片,有利于确保木薯产量和养分积累利用。     

木薯SBEI基因片段克隆及块根特异性反义表达载体的构建

为了抑制木薯支链淀粉的合成,提高直链淀粉含量,改变木薯淀粉结构,培育工业用燃料酒精型木薯品种,本研究利用RT-PCR方法,用木薯块根cDNA克隆获得支链淀粉合成的关键酶基因SBEI的部分片段,对其进行序列分析表明与GenBank序列高度同源,同源性为99.22％;并以pBI121为基础,构建了以块根特异性表达启动子Sporamin驱动的SBEI基因反义结构的植物表达载体。     

干旱胁迫与正常供水钾肥影响甘薯光合特性及块根产量的差异

【目的】干旱胁迫影响甘薯叶片光合特性及块根产量,研究通过施肥缓解干旱胁迫机理可为甘薯抗旱高产栽培提供理论依据。【方法】选用食用型甘薯品种“泰中6号”为材料,以硫酸钾(K2SO4)为供试肥料,水分处理设为土壤最大持水量的60%~70%(正常供水W1)和30%~40%(干旱处理W0); 钾肥设K0、 K1、 K2、 K3四个水平,K2O用量分别为0、 12.0、 24.0和36.0 g/m2。分析不同钾肥用量对不同生长时期甘薯叶片相对含水量、 叶绿素荧光参数、 光合特性及收获期块根产量的影响。【结果】在干旱胁迫和正常灌水条件下,施钾处理均显著增加了甘薯叶面积和叶片叶绿素含量,提高净光合速率(Pn),增加光合产物的生产和积累,提高块根产量和收获指数。两种水分条件下,块根产量均以K2处理最高, 干旱胁迫下K2与K3处理差异显著,正常灌水处理不显著。两种水分条件下,甘薯叶片光合参数对钾肥的响应存在显著差异,干旱胁迫下施钾使叶片水分利用效率(WUE)增大,气孔导度(Gs)降低,气孔阻力增大,蒸腾速率(Tr)和胞间CO2浓度(Ci)降低,水分蒸腾量减少; 而正常灌水条件下上述指标对钾肥的响应趋势相反。两种水分条件下施钾均可以增大叶片相对含水量(RWC),提高实际光化学效率(ΦPSII)和最大光化学效率(Fv/Fm),但是干旱胁迫下施钾增幅较大。【结论】干旱胁迫下适量施钾可以提高甘薯的抗旱性,增加甘薯产量,过量施钾使甘薯产量显著降低,而正常水分供应时,稍多钾肥对产量影响不显著。干旱胁迫与正常灌水条件下施钾对叶片光合参数的调控效应存在显著差异。施用钾肥可增大叶面积,提高叶绿素含量和光合性能,调节叶片气孔关闭,增大叶片气孔阻力,减少水分蒸腾损失,增加叶片相对含水量,提高水分利用效率和净光合速率; 施钾还能提高叶片PSⅡ原初光能转换效率和实际光化学效率,减少过剩激发能对光合机构的破坏,提高甘薯叶片的光合能力。干旱条件下钾肥的调节功能优于正常水肥供应。     

Nitrogen,Phosphorus and Potassium Interactions in Upland Rice

Upland rice is an important crop in South America, including Brazil. Nutrient interactions are important in determining crop yields. A greenhouse experiment was conducted to evaluate interaction among nitrogen (N), phosphorus (P), and potassium (K) in upland rice production. The treatments applied to upland rice grown on an Oxisol were three levels of N (N₀, N₁₅₀ and N₃₀₀ mg kg^?1), three levels of P (P₀, P₁₀₀ and P₂₀₀ mg kg^?1) and three levels of K (K₀, K₁₀₀ and K₂₀₀ mg kg^?1). These treatments were tested in a 3 × 3 × 3 factorial arrangement. Grain yield, shoot dry weight, plant height, root dry weight, maximum root length, panicle number, 1000-grain weight, and grain harvest index were significantly influenced by N, P, and K treatments. The treatment that did not receive P fertilization did not produce panicle or grain. Hence, P was most yield-limiting nutrient compared to two other nutrients. At the N₀P₀K₀ treatment, rice did not produce grains, indicating severe deficiency of these nutrients in Brazilian Oxisols. Maximum grain yield was obtained with the N₃₀₀P₂₀₀K₂₀₀ treatment. Grain yield had significant positive association with plant height, shoot dry weight, root dry weight, maximum root length, 1000-grain weight, panicle number, and grain harvest index. Among these growth and yield components, shoot dry weight had the highest positive association with grain yield and root length minimum positive association with grain yield. Hence, adopting adequate soil and crop management practices can improve growth and yield components and increase grain yield of upland rice.     

Comparing Application Methods for Boron Fertilizer on the Yield and Quality of Tobacco (Nicotiana tabacum L.)

The present study is based on the hypothesis that different methods of supplying boron (B) may have different effects on the yield and quality performance of tobacco crop. A field experiment was conducted to study the effect of different methods of B fertilization on the yield, quality, and leaf composition of flue-cured Virginia tobacco (cv. K-399) in 2007 at the Pakistan Tobacco Research Station, Mansehra. Three different methods (i.e., foliar spray, soil application, and root dipping at the rates of 0.25 kg ha^–1, 1 kg ha^–1, and 0.5 mg B L^–1, respectively) in the form of boric acid along with a control (where no B was applied) were used in a randomized complete block design and replicated four times. Results revealed that different methods of B application significantly affected tobacco yield, quality, and nutrient uptake compared to the control. Maximum leaf area of 707 cm², green leaf yield of 18553 kg ha^–1, cured leaf yield of 2314 kg ha^–1, grade index of 79%, nicotine content of 2.54%, and sugar content of 18.35% were noted in the treatment plot where B was applied as a foliar spray; however, in a few cases, there was no significant difference found among different methods of B application. Chloride and potassium contents were not significantly affected by any method of B fertilization. The B fertilization increased the concentration of this element in tobacco leaf, and a maximum concentration of B 48.55 mg kg^–1 was noted in the foliar spray treatment. Moreover, fertilizer-use efficiency for different methods of B application revealed that foliar spray is more efficient as compared to soil application and root-dipping methods. Nutrient ratios to B such as potassium (K) / B and chloride (Cl) / B considerably decreased in tobacco leaf with increases in the concentration of B in leaves. These ratios provided some indication of the interrelationship of B with these nutrients in tobacco plants. Results also revealed that K/B and Cl/B ratios closely correlated with the grade index of tobacco leaf, and good grades of tobacco were found to be at a K/B ratio of 682 and a Cl/B ratio of 148 under the experimental conditions. The overall results indicated that the B foliar spray at the rate of 0.25 kg ha^–1 significantly increased the yield, quality, and the nutrient uptake by the tobacco crop under the prevailing conditions and was more effective than other methods of B application.     

Carrot root size distribution in response to biostimulant application

In 2009–2011, in Poland (53°13′N, 17°51′E), field experiments were conducted concerning the influence of biostimulants Kelpak SL and Asahi SL on the size grades of yield of carrot cv. ‘Karotan’. Kelpak SL is produced from seaweed Ecklonia maxima; Asahi SL is composed of nitrophenols. Biostimulants were sprayed from fourth-leaf stage of carrot, once, twice or three times in growing period. Seaweed extract was used at total doses of: 0, 2, 3, 4, 5, 6 and 7?l?ha^?1, while Asahi SL at 1?l?ha^?1. It was found that biostimulants had a favourable effect on total and commercial root yield, but this effect was dependent on the type of preparation, the dose, the time and the number of treatments. The best results in increasing the commercial yield were achieved after a single application of Kelpak SL at doses 2 or 3?l?ha^?1 at the fourth-leaf stage (13.1% and 12.4% respectively, compared to the control). Both biostimulants Kelpak SL and Asahi SL positively affected the root size distribution by increasing the yield of medium roots (1.9–3.8?cm in diameter) as well as large roots (3.8–5.0?cm), by 30.5% and 15.8%, respectively.     

Soil Test and Plant Tissue Analysis as Diagnostic Tools for Fertilizer Recommendations for Cassava in an Ultisol

Soil- and plant-based fertilizer recommendations hold promise for increasing farmers’ incomes with high-input crops such as cassava. Considering the significance of cassava for the food, nutritional, and economic security of a half billion people globally and the positive response of the crop to fertilizer and manure applications in terms of tuber yield and quality through starch improvement and cyanogenic glucoside reduction, these recommendations were validated and popularized in two districts of Kerala State. Soil and plant samples from nine major cassava-growing districts of Kerala were analyzed for soil reaction, organic carbon, and essential nutrients, which formed the basis for the recommendation. The soil-test-based recommendation [nitrogen (N)–phosphorus (P)–potassium (K)–zinc (Zn) at 82:6.3:68:2 kg ha^?1 along with farmyard manure (FYM) at 6.25 t ha^?1] resulted in the greatest benefit–cost ratio of 1.75 with improvements in tuber and soil quality.     

Yield Maximization in Cassava through a Systematic Approach in Fertilizer Use

Abstract

Maximum yield research (MYR) and maximum economic yield systems (MEY) are important under the present situation of increased demographic changes, which have reduced the per capita availability of both land and food. Among root and tuber crops, cassava is found in a variety of production systems and performs well under various levels of management from low‐input to high‐input systems. A systematic approach in fertilizer use involves the determination and elimination of soil nutrient constraints for balanced supply of all potentially deficient essential nutrients for sustainable high yield. In the systematic approach of determining optimal fertilizer for cassava (Manihot esculenta Crantz) in a Typic Kandiustult soil of Kerala, India, studies on critical levels of nutrients, original nutritional status of the soil, its sorption capacity, and greenhouse/screenhouse nutrient survey were carried out. The critical levels of phosphorus (P) and potassium (K) were determined as 8.23 and 43.5 µg g^?1, respectively. The preliminary analysis of the soil of the experimental site revealed the overall fertility status as very poor. The sorption studies conducted for P, K, copper (Cu), zinc (Zn), manganese (Mn), sulfur (S), and boron (B) indicated P, K, S, and B were limiting in this particular soil. The quantities of these nutrients needed to optimize the soil nutrient status were determined from the preliminary soil analysis, critical levels of nutrients, and sorption curves and found to be 136 µg mL^?1 P, 0.338 meq 100 mL^?1 K, 20 µg mL^?1 S, and 6.025 µg mL^?1 B, respectively. From the greenhouse nutrient survey, N, P, K, and calcium (Ca) were seen as limiting nutrients for this soil; therefore the optimum treatment for cassava was fixed as N‐P‐K at 100:300:300 kg ha^?1, respectively. Field experiments were conducted for two seasons with different levels of the optimum treatment using a short duration (6–7 months) cassava variety, Sree Vijaya. The optimum treatment gave a yield of 43.41 t ha^?1, whereas the yield under the existing practice recommendations was 20–25 t ha^?1. Economic analysis showed this optimum treatment as the best in terms of highest gross return (Rs 1,31,125/‐), net return (Rs 83,150/‐), added return (Rs 70, 178/‐), added profit (Rs 56,142/‐), and benefit cost ratio (BCR) (2.73).     

不同氮肥施用方式下春玉米根系时空分布特征

通过剖析不同氮肥施用方式下,玉米根系统随生育进程在0～ 60 cm不同土层内分布特征及地上部产量和氮累积量的变化,以期为氮肥合理施用提供理论依据.以先玉335为供试品种,进行了4年田间定位试验.设3个处理:无氮区(N0);氮肥一次性基施200kg/hm2 (N1);氮肥分次施用(N2),基肥50 kg/hm2,拔节期1...     

腐植酸钾对食用甘薯品种钾吸收、利用和块根产量的影响

甘薯属于喜钾作物,增施钾肥是提高甘薯块根产量的重要措施之一;而腐植酸具有促进作物生长、提高肥料利用率等作用。为探讨腐植酸与钾肥配合施用对食用甘薯钾吸收利用以及块根产量的影响,本研究利用自行制备的两种腐植酸钾肥料,选用食用甘薯品种“北京553”于2005年在山东农业大学农学试验站进行了研究。试验采用块根膨大过程定期取样和收获期测产相结合的方法,观察了块根膨大过程中植株地上部鲜重/块根鲜重（T/R）比值、叶片和块根含氮量/含钾量（N/K）比值以及块根膨大速率的变化及其与块根产量的关系,同时分析了钾素生产效率和钾肥利用率在处理之间的差异。结果表明,施用适量钾肥可以降低植株T/R比值以及叶片和块根的N/K比值,提高块根膨大速率,提高收获期生物产量及其干物质在块根中的分配率,增产24.18%。但是,施用钾肥降低了钾素生产干物质和块根的效率。施用适量腐植酸可以降低块根N/K比值,提高叶片N/K比值,提高块根膨大速率以及收获期的生物产量,增产5.70%。同时,施用腐植酸提高了钾素产干物质和块根的效率。与等量氧化钾对照比较,在块根膨大前、中期,施用腐植酸钾可以降低植株T/R比值以及叶片和块根的N/K比值,提高块根膨大速率;块根产量提高8.11%～9.50%。同时,腐植酸钾肥料的吸收利用率和农学利用率都显著提高。     

Effect of Sheep Manure and Its Produced Vermicompost and Biochar on the Properties of a Calcareous Soil after Barley Harvest

ABSTRACT

Conversion of manures to vermicompost and biochar may alleviate some negative effects of manure application to soil but the efficiency of the produced vermicompost and biochar as compared to their feedstocks is not well-known. In the current investigation, we compared the effects of sheep manure and its derived vermicompost and biochar (pyrolyzed at 400°C for 4 h) on the properties of a calcareous soil that planted with five cultivars of barley (Behrokh, Khatam, Reyhaneh03, Fajr 30 and Nimrooz) for 60 days. Different soil properties and availability of nutrients and barley yield were determined after plant harvest. The biochar significantly increased barley yield rather than control (4.20 vs. 3.57 g pot^?1), but sheep manure and vermicompost had no effect on it (3.51 and 3.37 g pot^?1, respectively). Fajr 30 and Nimrooz (3.52 and 3.42 g pot^?1, respectively) had significantly lower yield than other cultivars. Biochar increased soil pH up to 8.2. Soil salinity was increased by application of all organic materials (increase to 16–36%). Cation exchange capacity (CEC) and organic matter content of soil were also increased by all organic materials application (0.4–0.9 cmol kg^?1 and 0.33–0.50%, respectively). All organic materials increased total nitrogen (N), but this increase was the highest with sheep manure application (53%). The availability of phosphorus (P) and potassium (K) was increased significantly by application of all organic materials, and this increase was the highest with biochar application (19 and 309 mg kg^?1, respectively). Biochar application had no effect on the availability of micronutrients, but application of sheep manure and vermicompost increased the availability of iron (Fe) (0.62 and 0.48 mg kg^?1, respectively) and zinc (Zn) (0.18 and 0.37 mg kg^?1, respectively). Generally, organic materials may change the status of soil nutrients via change in soil pH, organic matter content, release of nutrients, increase in soil CEC and formation of soluble complex with nutrients.     

The effect of vesicular-arbuscular mycorrhizal inoculation on nutrient uptake and yield of alley-cropped cassava in a degraded Alfisol of southwestern Nigeria

Leaf and root (tuber) nutrient uptake patterns of cassava (Manihot esculenta Crantz) alley-cropped with gliricidia (Gliricidia sepium), leucaena (Leucaena leucocephala), and senna [(Senna (syn. Cassia) siamea] as influenced by vesicular-arbuscular mycorrhizal (VAM) inoculation in a degraded Alfisol were investigated in consecutive years. The cassava plants were mulched with fresh prunings of each hedgerow tree species at 2-month intervals in the second and third years of alley cropping. While VAM inoculation significantly influenced the root uptake of nutrients, the leaf uptake was not affected except for the uptake of P. In most cases, there was no difference in the nutrient concentration between inoculated and uninoculated plants, either in the leaf or in the root, indicating that the productivity of cassava was regulated by the amount of nutrients the roots could absorb. In spite of similar total soil N in all inoculated and uninoculated alley-cropped cassava plots and similar exchange-able soil K contents in inoculated and uninoculated alley-cropped cassava plots with leucaena and senna, greater uptake of N, P, and K and greater concentrations of K were observed in roots of inoculated alley-cropped cassava with gliricidia and leucaena than with senna. These results indicated that greater mineralization and availability of nutrients to cassava roots from prunings of nodulating gliricidia and leucaena than from non-nodulating senna may be important, particularly with efficient VAM inoculation, in these alley-cropping systems. Also, for similar nutrients in the inoculated and uninoculated cassava soils alley-cropped with each hedgerow species, VAM inoculation significantly enhanced cassava root dry weights, indicating that an effective VAM fungus can be an agent of greater nutrient uptake in a competitive environment.     

土壤通气性对甘薯养分吸收、~(14)C同化物分配及产量的影响

选用鲁薯 7号和徐薯 1 8为材料 ,研究了土壤通气性对甘薯无机养分吸收、14 C 同化物分配和块根产量的影响。结果表明 :改善土壤的通气性可以增加叶片中钾、钙、锰、硼和锌的含量 ,增加块根中钾和钙的含量 ,减少块根中锰、硼和锌的含量 ,促进14 C 同化物由叶片向块根的运转和分配 ,提高块根中淀粉含量 ,极显著地提高了块根的产量。本文讨论了矿质元素在促进14 C 同化物由叶片向块根运输中的作用     

Root distribution patterns of white yam (Dioscorea rotundata Poir.): a field study

Abstract

The productivity of white yam (Dioscorea rotundata Poir) must increase to sustainably meet the demand of the increasing populations in the developing world where this is a staple crop. Although this could be achieved through the use of mineral fertilizers, reports indicate limited effects of these inputs on tuber yield. We hypothesized (i) that D. rotundata has a small and shallow root system and (ii) that this root system does not respond to mineral fertilizer application. Two field experiments were conducted in Côte d'Ivoire in year 1 and in year 2 to test these hypotheses. In the first field experiment we measured biomass production, as well as root density during plant growth in fertilized and unfertilized plots while in the second experiment, we analysed the distribution pattern of roots in horizontal and vertical root profiles in fertilized plots. The root system of D. rotundata consisted of seminal, adventitious and tubercular roots. Only the adventitious roots remained alive until the end of the growth cycle. The root length density was very low with a maximum of 0.25 cm cm^?3. No roots were observed in the 15–30 cm horizon at 50 cm from the plant's crown. The horizontal and vertical root maps revealed that roots were mostly distributed in clumps, and there was a good correlation between the two methods of root sampling for this species. Fertilizer application had no significant effect on plant biomass, fresh tuber yield or on root growth. However, thinner and longer roots and higher tuber yields were observed in year 1 than in year 2. The different weather conditions and more specifically the higher soil temperature might explain the results obtained in year 1. Therefore, it could be recommended to farmers not to fertilize D. rotundata.     

Nutrient use efficiency and harvest index of cassava decline as fertigation solution concentration increases

Response of cassava (Manihot esculenta Crantz) to fertigation as a form of nutrient delivery is unknown. The objectives of this study were to establish a balanced nutrition and to enhance agronomic nutrient use efficiency (ANUE) of cassava under fertigation. This study was conducted in the greenhouse and in the field. In both, the results showed a similar trend. There were six fertigation concentrations and three cassava varieties, selected for their duration of growth in the field. Shoot biomass of the long‐duration variety (Nalumino) was the highest, even though its dry root yield was the lowest (10.18 t ha^?1) among the varieties. In contrast, the medium‐duration variety (Kampolombo) produced the highest dry root yield (20.34 t ha^?1) and a lower shoot biomass. The highest root yield of the shortest‐duration variety (Mweru) was achieved at 200 mg N, 30 mg P, and 200 mg K L^?1 (155.0, 23.3, 155.0 kg N, P, K ha^?1), while Nalumino's was at 70 mg N, 7 mg P, and 70 mg K L^?1 (54.3, 5.4, 54.3 kg N, P, K ha^?1). ANUE and harvest index of these varieties declined as the fertigation concentrations increased. Additionally, the correlation between concentrations of N in the youngest fully expanded leaf (YFEL) blades and dry root yields was the lowest (R² = 0.5488), whereas P and K were R² = 0.7237 and R² = 0.8006, respectively, an indication that nutrient concentrations in the leaf, especially N, cannot easily be used to predict root yield. When cassava reaches nutrient sufficiency, mainly N, its accumulation in the leaf continues without significant increase in the root yield.