Phenotypic nutrient up-take differences in an alley cropping system in semi-arid Machakos, Kenya

Alley cropping of Cassia siamea and maize was studied in semi-arid Kenya for soil fertility improvement. Katumani composite maize was planted except in the short rains of 1988 (SR88) when a hybrid variety was sown. Therefore the grain yield per row increased differently in the alley cropped maize (CM). Sole maize (SM) and CM yields were higher in SR88 than in the long rains of 1988 (LR88) by 62nd 38°while yields from the same treatments in LR89 were only 21nd 45␘f those in SR88. These differences in relative maize yields are attributed to differences between the two maize varieties in competition under nutrient stress conditions

Evaluation of Leucaena leucocephala leaf prunings as a source of nitrogen for maize

Prunings of leucaena [Leucaena leucocephala (Lam.) De Wit] have long been regarded as a useful alternative to N fertilizer, but N use efficiency by crops is often low. The potential exists to synchronise nutrient release with crop nutrient demand through variation in the rate and placement of prunings. A 2x2x3 factorial experiment was conducted to evaluate the potential of leaves of leucaena to supply N to maize (Zea mays L.) plants grown in pots of soil (Grossarenic Paleudult) under glasshouse conditions. Factors tested were two rates of application (3 and 6 Mg ha-1), two methods of placement (surface vs incorporation), and 3 levels of N fertilizer (0, 50, and 150 kg ha-1 equivalent of urea in solution form). Surface applied prunings significantly increased maize shoot dry weight with increasing levels of N fertilizer. Although incorporation of prunings increased maize shoot dry weight, the incorporated treatments did not show any significant response to N fertilizer, indicative of adequate N supply from prunings. Both shoot and total dry weight significantly increased with increasing rates of prunings applied. Nitrogen recovery was increased by applying prunings together with N fertilizer. There was a higher N recovery with incorporation compared to surface application. Prunings applied at a rate of 3 Mg ha-1 gave higher %N recovery than 6 Mg ha-1. At the final harvest date, application of 6 Mg ha-1 of prunings produced taller plants than 3 Mg ha-1.Les emondes de leucaena (Leucaena leucocephala (Lam.) De Wit) ont longtemps ete considerees comme une alternative aux engrais azotes, mais l'utilisation efficace de N par les plantes est souvent limitee. Il existe le potentiel synchroniser la liberation des substances nutritives avec la demande des nutritifs par une variation du nombre et du placement des emondes. Une experience factorielle (2x2x3) a ete effectuee pour evaluer le potentiel des feuilles de leucaena de fournir de lte aux plantes de mas (Zea mays L.) eleves en pots de terre (Grossarenic Paleudult) en conditions de serres. Les facteurs examines etaient les suivants: taux duplication (3 et 6 Mgha-1), deux methodes de placement (surface vs incorporation), et trois niveaux de fertilisation d'azote (0,50 et 150 kg ha-1) equivalent de en forme de solution. Les emondes appliquees la surface font augmenter d'une facon significative le poids sec des pousses de mas avec des niveaux plus eleves d'engrais azotes. L'incorporation des emondes augmente le poids sec des pousses de mas, mais il n pas de reponse significante avec les engrais azotes; ceci indique que sous cette forme duplication, les emondes fournissent de lazote d'une facon efficace. Le poids sec des pousses et le poids sec total augmentaient avec des taux plus eleves dndes. La recuperation dte augmentait par une application simultanee dndes et drais azote. La recuperation d'azote etait plus importante quand les emondes incorporees etaient comparees avec une application la surface. 3 Mg ha-1 dndes appliquees donnaient une plus grande recuperation (%) d'azote que 6 Mg ha-1. Au moment de la recolte, 6 Mg ha-1 demondes appliquees produisaient des plantes de plus hautes tailles que 3 Mgha-1

Combining napier grass with leguminous shrubs in contour hedgerows controls soil erosion without competing with crops

We established hedges/barriers of calliandra (Calliandra calothyrsus Meissner), leucaena (Leucaena trichandra (Zucc.) Urban)) and napier grass (Pennisetum purpureum chumach) and combination hedges of either calliandra or leucaena with napier grass on slopes exceeding 5% to study the effect of vegetative barriers on productivity of arable steeplands in central Kenya. Hedges/barriers were pruned regularly and biomass incorporated into the plots. Hedge plots were monitored for soil fertility, soil losses and maize crop yield changes. Inorganic-N concentration in the tree hedge plots was higher than in the control and napier barrier plots after 20 months. Napier grass barriers were the most effective in reducing erosion losses across the two seasons. The effectiveness of napier grass to significantly reduce soil erosion was detectable in one year old napier barriers. Soil loss from all the other one year old vegetative treatmentswas similar to soil loss from the control. Seventeen month old combination hedge plots recorded lower soil losses than tree hedges of the same age (P = 0.012). Maize crop yields throughout the trial period were high and similar for leguminous and combination hedge plots, but lower in the napier grass and control plots. Overall, we observed that the combination hedges seemed to provide a win-win scenario of reduction in soil erosion combined with improvement of maize crop yields and soil fertility enhancement.We conclude that vegetative hedges have a potential for improving soil productivity in arable steep-lands of the central highlands of Kenya, and that in adoption of vegetative hedges for this purpose there are trade-offs between soil conservation, soil fertility and maize crop yields to be considered

Effect of incorporating Cassia siamea prunings on maize yield in an alley cropping trial in semiarid Kenya

The influence of soil-incorporated Cassia siamea prunings on nutrient status of maize leaves, grain and yield was studied in an alley cropping experiment in semiarid Machakos, Kenya, during the 1988 long and short rainy seasons. The trial was established in 1983 and in all the seasons Katumani composite B maize was sown, except in the short rains of 1988 when Hybrid 511 was planted. Plots consisted of 3 cropped alleys between cassia hedges spaced at 3.6 m apart. The hedges were lopped at the beginning of every season (on-set of rains) and the prunings incorporated into the alleys one day before maize seeds were sown. The control plots had no hedges and hence no prunings were incorporated. Incorporation of prunings into the soil increased nutrient concentration in the maize leaves, grains and soil in the treatment plots compared to the controls. Maize grain yield on a per row basis was also higher in the plots that received prunings application compared to the controls. However, on an area basis, the yield increase was insufficient to compensate for the area lost to the Cassia siamea shrubs.L'impact des emondes de Cassia siamea inorpores dans le sol sur la production et la composition minerale des feuilles de mais et des grains a ete etudie dans une experimentation de culture en couloirs. Celle-ci a ete organisee en region semi-aride de Machakos au Kenya pendant les grandes et petites saisons pluvieuses de 1988. L'essai a ete mis en place en 1983. Chaque saison, le compose B du mais connu sous le nom de Katumani etait serre, sauf pendant les petites saisons pluvieuses de 1988 lorsque l'hybride 511 etait plante. Les parcelles etaient constituees de 3 allees cultivees entre les haies de cassia distantes entre elles de 3.6 m. Les haies etaient elaguees au debut de chaque saison pluvieuse. Les emonoles etaient ensuite incorporees dans les allees un jour avant la semence des graines. Les parcelles de contrle n'avaient pas de haies; les emondes n'y etaient donc pas incorporees. L'incorporation des emondes dans le sol des parcelles de traitement augmentait la teneur des elements mineraux nutritifs dans les feuilles et les grains de mais. Cela n'etait donc pas le cas dans les parcelles de contrle. La production des grains de mais par rangee s'est egalement averee plus importante dans les parcelles ou les emondes ont ete appliquees que dans celles de contrle. Cependant, en terme de surface la croissance de la production etait insuffisante pour pouvoir compenser la perte de la surface due a la presence des arbustes de Cassia siamea

Soil nutrients and crop yield response to conservation-effective management practices in the sub-humid highlands agro-ecologies of Kenya

Crop productivity in most smallholder farming systems in Sub-Saharan Africa experience low use of soil amendment resources, low and erratic rainfall, frequent dry spells, and droughts. Rain-fed agriculture has a high crop yield potential if rainfall and soil nutrient input resources are utilized effectively. Thus, in 2011, we set up an on-farm experiment in Meru South (sub-humid) and Mbeere South (marginal sub-humid) sub-counties in upper Eastern Kenya to assess conservation-effective management (CEM) practices effects on maize (Zea Mays L.) yields response and soil nutrients. The CEM practices were; tied ridging (TR), mulching (MC), and minimum tillage (MT), with conventional tillage (CT) as a control. There were frequent dry spells and droughts during the experimental period. The experiment ran for four seasons, from the long rains season of 2011 (LR11), short rains seasons of 2011 (SR11), long rains season of 2012 (LR12), short rains 2012 (SR12), and long rains season of 2013 (LR13). In Meru South, TR and MT treatments had significantly higher phosphorus content (100% and 66%, respectively) than the control. Also, in the same site, Cu and Zn were high in MT than in CT treatments. In the Mbeere South site, the aboveground biomass yield was significantly higher in TR treatment (by 71%) than CT during SR11, while in LR12 season, it significantly increased by 72% and 46% under MC and TR treatments, respectively, than the control. The TR treatment had significantly higher aboveground biomass than the control (84% and 115%) in the SR12 and LR13 seasons. In Meru South, MC treatment had significantly higher aboveground biomass, which was significantly higher, by 39%, during the SR11 season and 46% in TR treatment in SR12 season than the control. This study highlighted tied ridging as the best-fit practice for enhancing maize crop aboveground biomass production in rain-fed farming systems of marginal lands and sub-humid regions receiving unreliable rainfall. Further, we recommend longer-term experimentation to explore CEM effects on soil nutrients

Effect of incorporating Cassia siamea prunings on maize yield in an alley cropping trial in semiarid Kenya.

(African Crop Science Journal, 1997 5(2): 201-208

Tied-ridging and soil inputs enhance small-scale maize productivity and profitability under erratic rainfall conditions in central Kenya

Deficits in soil moisture and low soil fertility are the major constraints to smallholder farming systems in the SSA (sub-Saharan Africa) region. This study evaluated the effects of tied ridging and selected soil fertility inputs on; soil water content at different depths, maize yields, and economic returns. The treatments were: Tithonia diversifolia + inorganic fertilizer, manure + inorganic fertilizer, inorganic fertilizer, and control with or without tied ridging as the soil water conservation factor. Data were subjected to analysis of variance, and the means were separated using LSD at p ≤ 0.05. Treatments with Tithonia diversifolia or manure combined with inorganic fertilizer with or without tied ridging consistently affected soil water content positively. The effect of tied ridging on soil water content was greater during the short rain season compared to the long rains. In addition, there was evidence that tied ridging and organic soil inputs resulted in greater soil moisture conservation during the critical silking and tasselling maize phenological stages during the short rain season. Treatments had significant effects on grain and stover yields during the long rain 2016 season (p < 0.0001 and p = 0.0477, respectively) and the short rain 2016 season (p < 0.0001 and p = 0.0035, respectively). The highest (4.87 Mg ha−1) maize grain yield was recorded in Tithonia diversifolia plus inorganic fertilizer under tied ridging in the long rain 2016 season, while manure + inorganic fertilizer without tied ridging gave the highest yields (1.27 Mg ha−1) in the short rain 2016 season. The highest net benefits of US$1229.90 ha−1 and US$ 171.57 ha−1 were recorded under Tithonia diversifolia plus inorganic fertilizer with tied ridging during the long and short rain seasons, respectively. Overall, the best-performing treatments in yields and profitability were those that combined organic and inorganic fertilizers, regardless of the presence or absence of tied ridging. Climate-smart agricultural strategies combining tied ridges and organic inputs should be an integral component of farmer management if losses related to soil fertility and water stress are to be minimized under erratic rainfall regimes in the semiarid farming systems of the SSA region

Soil organic C stabilization and thresholds in C saturation

J.M. Kinyangi is ILRI authorWhen building soil organic matter (SOM) contents in agricultural production systems, stabilization of both pre-existing as well as added C is important. A laboratory mineralization experiment was conducted over 374 days to evaluate the effect of pre-existing SOM on soil C mineralization after addition of organic matter (OM) using sugar cane. The SOM gradient used here stretched from 21 to 106 g C kg−1 soil and was a result of different periods of continuous cultivation of 5, 20, 35 and 105 years in comparison to a forest soil. The rate of organic C mineralization was found to be dependent on the status of pre-existing soil organic C (SOC). Highly degraded soil which had been under continuous cultivation for 35 years and more showed the highest rate of C mineralization per unit SOC (117.9 mg C g−1 C) while forest soil had the lowest amount of C mineralized per unit SOC (73.5 mg C g−1 C). Forest soil had the highest amount of increased C mineralization as a result of organic matter (OM) additions (8.0 mg C g−1 soil) followed by the highly degraded soil that had been under cultivation for 105 years (5.5 mg C g−1 soil). Additional mineralized C as a function of time after forest conversion declined progressively within the first 20 years of continuous soil use. Soil which had been under continuous cultivation for 20 years had the lowest amount of additional mineralized C (4.0 mg C g−1 soil). SOM stabilization efficiency in the studied soils appears to be highest with intermediate cultivation history of about 20 years. These soils that have been recently converted to cultivation also appear to have a greater ability to stabilize added OM than the most degraded soils investigated in this study. It is thus advisable to provide intervention strategies to reverse SOM decline for farming communities at an intermediate stage before the soils are highly depleted of SOC

Effects of selected soil and water conservation technologies on nutrient losses and maize yields in the central highlands of Kenya

Mitigating nutrient loss is a prerequisite of sustainable agriculture in the tropics. We evaluated three soil and water conservation technologies (mulching, minimum tillage and tied ridging) for two cropping seasons (long rains 2011, short rains 2011) at two sites in the central highlands of Kenya. The objectives were: to determine effects of the technologies on runoff, sediment yield and nutrient loads in sediment, and to assess influence of the technologies on maize yields. Experimental design was a randomized complete block with 3 treatments replicated thrice. At the beginning of experiment, soil was sampled at 0–15 cm depth and analyzed for pH, N, P, K, C, Ca and Mg. Mulch was applied at a rate of 5 t ha−1. Runoff was sampled, sediments extracted by drying in oven at 105 °C, and analyzed for NPK and C loads. Data were subjected to analysis of variance using SAS 9.1.3 and means separated using Fishers’ LSD at 5% level of significance. Results showed reduced nutrient losses with the technologies. In Meru South, sediment yield was reduced by 41 and 7% during long rains 2011 (p = 0.03), and by 71 and 68% during short rains 2011 (p = 0.01) under mulching and minimum tillage, respectively. Runoff and maize yields were positively influenced by mulching. In Mbeere South, sediment yield was lower under soil and water conservation technologies. Runoff was reduced by 52 and 49% during long rains 2011 and by 51 and 30% during short rains 2011 under tied ridging and mulching respectively, compared with control. Total crop failure occurred during long rains 2011 due to erratic rains. During short rains 2011 tied ridging and mulching increased maize yield by 94 and 75%, respectively, compared with control. This study highlights the importance of analyzing soil and water conservation technologies within rain-fed farming systems perspective in response to declining food production and supports a focus on tied ridging and mulching