Comparative performance of seventeen upperstorey tree species associated with crops in the highlands of Uganda

Trials were established at three sites in Uganda to test the suitability of multipurpose trees (MPTs) as upperstorey in crop lands to provide poles, small timber and fuelwood. The three sites were Kachwekano District Farm Institute (1°16 S, 29°57 E, 2000 m.a.s.l.) in Kabale District, Kabanyolo University Farm (0°28 N, 32°27 E, 1250 m.a.s.l.) in Mpigi District and Bushenyi District Farm Institute (0°34 S, 30°13 E, 1610 m.a.s.l.) in Bushenyi District. The MPTs were planted in single rows at intra spacing of 2 m and each plot contained seven or nine trees. On both sides of the tree row, crops were raised. Data on crop yields were collected every season, while data on the growth of the trees were collected four times each year.In terms of tree growth,Grevillea robusta, Casuarina cunninghamiana andAlnus acuminata performed well with height growth of 1.8–2.4 m per year at Kachwekano, while at BushenyiGrevillea robusta, Casuarina junghuhniana, Cupressus lusitanica andCedrela serrulata averaged 1.6–2.0 m height per year. At Kabanyolo,Melia azedarach, Cassia siamea, Jacaranda mimosifolia, Grevillea robusta andMaesopsis eminii had height increments ranging from 1.8–2.7 m annually. Crop yields were affected by the presence of the MPTs, withMaesopsis eminii being the most competitive (averaging 60% reduction, over five seasons). The crop rows nearest to the tree line were the most affected. OnlyAlnus acuminata seems to have had a positive effect on crop yields. The installation of a root mesh to reduce tree root competition for nutrients and water in four species increased yields in plots with MPTs by 5% (Melia azedarach) to 152% (Maesopsis eminii), but the control plot still had significantly higher bean yields, suggesting that shading could also be important. In the case of maize, suppression seems to be due mainly to root competition because after its elimination yields obtained thereafter did not differ significantly from those of the control except for the Maesopsis plots. The negative influence of the MPTs could, therefore, be minimized by periodically pruning the tree crowns and roots.     

渭北旱塬沟壑区不同立地条件刺槐林生长分析

渭北高原沟壑区主要立地类型土壤水分变化及对刺槐生长影响分析结果表明：土壤水分与刺槐生长之间关系密切,说明水分是影响刺槐生长的主要因素,地形和土壤则是划分渭北旱塬立地类型的主要因子。不同立地类型间刺槐高、地径生长量由大到小的序列为：沟底塌积土〉塬面黄土〉梁顶黄土〉沟底石砾土〉阳坡下部黄土〉阳坡上部黄土〉梁坡上部姜石粗骨土〉冲风口黄土〉梁顶姜石粗骨土〉沟坡中下部阳向黄土〉红胶土。     

水肥耦合对矮化富士苹果幼树的促长促花作用研究

采用311-A最优混合设计,以有机肥、无机肥(N:P2O5：K2O=1：0．7:1)和补充灌水量为主要因子,对无病毒矮化红富士幼树的生长发育和早实性进行了研究。结果表明,在渭北旱塬南缘,采取合理的水肥组合与管理措施,可显著改善矮化红富士幼树的营养状况,促进新梢生长和提早开花结实。在平水年,降水可满足幼树生长需要,补充灌水虽可促进春梢生长,但对提早开花结实有负作用;不施肥或施肥不足,则成为影响红富士幼树生长、发育和早实性的主要限制因子。增施有机肥(混合厩肥)24536kg／hm^2,无机肥N、K2O各459．86kg／hm^2、P2O5 321．90kg／hm^2,补充灌水35．86mm可使春梢生长量达到最大,对迅速扩冠成形极为有利;同时该施肥、灌水水平亦可使栽后第三年开花株率达70．1％。     

渭北黄土坮塬区苹果园土壤养分状况分析

采用常规方法测定了渭北黄土坮塬区110个苹果园的土壤养分含量,结果表明苹果园0～30 cm土层土壤有机质含量8.9～12.1 mg·kg-1,平均为10.05 mg·kg-1,属较低水平;有效氮、磷、钾供应状况大约为钾＞氮＞磷,按照农田土壤养分丰缺指标衡量,果园土壤普遍缺磷,约40％土壤缺氮,而钾素含量较为丰富;有效铁、锌、锰含量大部分在边缘值以下,其比例分别为铁64.5％、锌83.4％、锰91.3％,缺乏程度依次为Mn＞Zn＞Fe,远远不能满足苹果优质、高产之需要.     

陕西渭北地区苹果树腐烂病发生情况调查

为明确近年来陕西省苹果主产区腐烂病发生动态,于2009-2011年在渭北7个县区对不同树龄、不同品种的525个苹果园进行系统调查。结果表明,这些果园苹果树腐烂病发生普遍,平均病株率55%、单株平均新生病疤数1.5个、病情指数25、侧枝发病率14%,年份间除侧枝外,其他发病率没有明显性差异。不同树龄的富士苹果树发病情况调查显示,其平均侧枝发病率、病情指数差异显著,树龄大发病严重,16～20a树龄比6～10a树龄的果园发病率和单株平均新生病疤数分别高出58.89%和46.21%;富士、嘎啦和秦冠3个品种发病情况调查显示,其平均侧枝发病率差异显著,以秦冠发病最轻,且平均病株率和病情指数也明显低于其他品种;不同地域富士发病情况差异显著,渭北台塬西部区的腐烂病发生最为严重,渭北台塬东部区次之,渭北高原沟壑区发病最轻;栽植密度对富士果园发病影响显著,栽植密度大的果园其平均病株率、单株平均新生病疤数、病情指数、侧枝发病率均明显高于栽植密度小的果园。     

微生物有机无机复混肥对陕北苹果产量及品质的影响

通过在陕西渭北旱塬红富士苹果园设置肥效对比试验,探讨施用微生物复混肥与施用传统肥料对红富士苹果产量、品质的影响。结果表明：施用微生物研究所研制的苹果专用微生物复混肥后,产量与对照相比均有提高,最高增长幅度为28.82%,最低为3.06%;单果重平均为233.88 g,平均提高15.83%;商品果率平均为80.80%,平均提高8.67%;糖度平均为13.52%,平均提高4.79%;硬度平均为9.61 kg/cm2,平均提高3.58%。说明施用微生物复混肥在提高产量尧改善苹果品质方面效果显著。     

渭北旱塬不同秸秆覆盖量对土壤水分和春玉米产量的影响

为了探明不同秸秆覆盖量对渭北旱塬土壤水分及春玉米产量的影响,于2008－2009年在陕西合阳县旱农试验站进行了3个水平的秸秆覆盖量（4 500、9 000和13 500 kg/hm2）试验,以不覆盖为对照（CK）。2 a结果表明,3个处理0～200 cm土层平均土壤贮水量较CK均显著提高,分别增加16.52、25.52和34.04 mm（P＜0.05）;播后0～60 d,农田蒸散量较CK分别减少4.43、8.23（P＜0.05）和6.96 mm（P＜0.05）;9 000 kg/hm2处理2年平均籽粒产量及水分利用效率表现最优,较CK分别提高11.03%（P＜0.05）和9.25%（P＜0.05）,13 500 kg/hm2处理次之,4 500 kg/hm2处理最差。本研究表明,渭北旱塬春玉米生育期降水量低于390 mm时,不同秸秆覆盖量处理蓄水保墒及增产效应明显,且以9 000 kg/hm2覆盖量为宜。     

渭北旱塬结合夏闲地翻耕施肥效应

为了避免秋季施肥时多次翻耕土壤而损失水分,提高肥水利用率和生产率,对渭北旱塬结合夏闲地翻耕施肥效应（在７月中旬和８月中旬）进行了研究。结果表明,该施肥方式能提高小麦产量、增加土壤ＮＯ３＾－－Ｎ的积累和提高肥水利用率及生产效率,同时也能缓解秋播劳力紧张的矛盾,有利于适时适墒播种。     

Infiltration rates, surface runoff, and soil loss as influenced by grazing pressure in the Ethiopian highlands

Abstract. The effect of grazing pressure on infiltration, runoff, and soil loss was studied on a natural pasture during the rainy season of 1995 in the Ethiopian highlands. The study was conducted at two sites with 0–4% and 4–8% slopes at the International Livestock Research Institute (ILRI) Debre Zeit research station, 50 km south of Addis Ababa. The grazing regimes were: light grazing stocked at 0.6 animal-unit-months (AUM)/ha; moderate grazing stocked at 1.8 AUM/ha; heavy grazing stocked at 3.0 AUM/ha; very heavy grazing stocked at 4.2 AUM/ha; very heavy grazing on ploughed soil stocked at 4.2 AUM/ha; and a control with no grazing. Heavy to very heavy grazing pressure significantly reduced biomass amounts, ground vegetative cover, increased surface runoff and soil loss, and reduced infiltrability of the soil. Reduction in infiltration rates was greater on soils which had been ploughed and exposed to very heavy trampling. It was observed that, for the same % vegetative cover, more soil loss occurred from plots on steep than gentle slopes, and that gentle slopes could withstand more grazing pressure without seriously affecting the ground biomass regeneration compared to steeper slopes. Thus, there is a need for developing 'slope-specific' grazing management schedules particularly in the highland ecozones rather than making blanket recommendations for all slopes. More research is needed to quantify annual biophysical changes in order to assess cumulative long-term effects of grazing and trampling on vegetation, soil, and hydrology of grazing lands. Modelling such effects is essential for land use planning in this fragile highland environment.     

渭北地膜覆盖小麦最佳种植模式及微生境效应研究

以露地小麦为对照,对膜上穴播和膜侧沟播两种模式进行比较研究。两地多年试验结果表明,起垄覆膜沟播模式在小麦生育期具有聚水、保墒、增温、透光等作用,是符合渭北自然条件的旱地小麦高产、稳产最佳模式;其微生境效应,除冬前增温效果没有膜上穴播模式明显外,其它诸如聚水保墒效果、土壤微生物数量、土壤养分吸收以及水分利用效率等均好于膜上穴播模式。