ABSTRACT
Acidic soils pose a major challenge for crop production in heavily weathered tropical soils, especially due to the high toxicity of aluminum (Al), low cation exchange capacity, and low availability of phosphorus (P) to plants. Lime application was recommended to alleviate soil acidity problems. Granular CaCO3 lime was introduced into the Kenyan market as an alternative to powdered CaCO3 and CaO-lime for small Kenyan farms, providing uniform distribution and efficient application. The aim of this study was therefore to investigate the effectiveness of different types of powdered and granular lime individually and in combination with mineral fertilizers in improving soil properties and maize yield. The study was conducted at two sites, Kirege (extremely acidic) and Kangutu (moderately acidic). Experiments were conducted in a randomized complete block design repeated four times in two consecutive seasons: long rain (LR) in 2016 and short rain (SR) in 2016. Three types of lime were applied before planting. Selected chemical properties of the soil were analyzed before and after the experiment. Maize and stover yield data were collected and analyzed. Results showed that lime application significantly increased soil pH and decreased exchangeable acidity. Powdered calcium carbonate (CaCO3) showed the highest pH increase in both extreme (+19%) and moderate (+14%) acid sites. All types of lime and fertilizer applications alone significantly increased the available soil P at both the seasonal and site levels. However, maize grain yield was lower with fertilizer alone or lime alone than with lime and fertilizer combination. Powdered CaCO3+ fertilizer was found to give the highest grain yields on both very acidic (5.34 t ha-1) and moderately (3.71 t ha-1) acid sites. In the study, combining powdered CaCO3 lime with fertilizers was most effective in improving acidic soils by decreasing soil acidity and increasing available phosphorus, which ultimately increased grain yield. The results of this study recommend the use of powdered CaCO3 as an effective and practical solution for farmers facing soil acidification problems.
ABSTRACT
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.
ABSTRACT
Soil acidity and phosphorus deficiency are some of the constraints hampering agricultural production in tropical regions. The prevalence of soil acidity is associated with phosphorus (P) insufficiency and aluminum saturation. We conducted a two-seasons experiment to evaluate soil phosphorus availability and exchangeable aluminum in response to phosphate rock and organic inputs in acidic humic nitisols. The field experiment was installed in Tharaka Nithi County in the Central Highlands of Kenya. The experimental design was a randomized complete block design with treatments replicated thrice. The treatments were: Green manure (Tithonia diversifolia Hemsl.) (60 kg P ha-1), phosphate rock (60 kg P ha-1), goat manure (60 kg P ha-1), Tithonia diversifolia (20 kg P ha-1) combined with phosphate rock (40 kg P ha-1), manure (20 kg P ha-1) combined with phosphate rock (40 kg P ha-1), Triple Super Phosphate combined with Calcium Ammonium Nitrate (TSP + CAN) (60 kg P ha-1) and a control (no input). During the long rains of the 2018 season (LR2018), Tithonia diversifolia + phosphate rock had a significantly higher reduction (67%) of exchangeable aluminum than the sole use of Tithonia diversifolia. Grain yield under TSP + CAN was the highest, followed by the sole organics during the LR2018. Tithonia diversifolia + phosphate rock resulted in a 99% and a 90% increase in NaHCO3-Pi compared to sole phosphate rock and sole Tithonia diversifolia, respectively. Tithonia diversifolia led to 14% and 62% higher resin-Pi and NaOH-Pi, respectively, compared to manure in the short rains of 2017 (SR2017). The increase in NaOH-Po after the two seasons was statistically significant in sole TSP + CAN. Based on the observed reduced exchangeable aluminum and additional nutrients like Ca, Mg, and K in the soil, sole organic inputs or in combination with phosphate rock treatments are feasible alternatives for sustaining soil phosphorus. Our findings underscore an integrated approach utilizing organic amendments combined with phosphate rock in acidic humic nitisols' phosphorus nutrient management.
ABSTRACT
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 62% and 38%, while yields from the same treatments in LR89 were only 21% and 45% of those in SR88. These differences in relative maize yields are attributed to differences between the two maize varieties in competition under nutrient stress conditions.
