Combined Effects of Legumes with Phosphorus Fertilizer on Nutrient Balances and Gross Margins in Maize (Zea mays L.) systems of Kabete sub-County, Kenya

Calculation of soil nutrient balances and gross margins (GM) is imperative in ascertaining effect of innovative technologies on soil fertility and farm profitability. A field experiment to evaluate effect of combined legumes and phosphorus fertilizer on soil N, P and K balances and crop GM in maize (Zea mays L.) systems was set up in Kabete Division, Kenya, in the long and short rainy seasons of 2012. The experimental set up was a randomized complete block design (RCBD) with a split plot arrangement. The main plots comprised cropping systems; (i) monocropping (sole maize), (ii) intercropping [white lupin (Lupinus albus L.)/maize (L/M) and chickpea (Cicer arietinum L.)/maize (CP/M)], and (iii) rotation [white lupin-maize (L-M) and chickpea-maize (CP-M)]. The split plots were phosphorus (P) fertilizers; Minjingu phosphate rock (MPR) and triple superphosphate (TSP), and (iii) no P fertilizer applied (CTRL). Soil N, P and K balances and gross margins were analyzed at plot level using NUTrient MONitoring (NUTMON - now known as MonQi) Tool box. Nutrient balances were negative across cropping systems and P sources except for K in M/CP (CTRL and TSP) intercrop. Significantly less negative N balances were obtained in maize monocrop (MPR), CP/M (CTRL) intercrop, CP-M (TSP) rotation, and L/M (MPR) intercrop. L/M (CTRL and TSP) intercrop and L-M (CTRL and TSP) rotation recorded more negative (highest losses) N balances. Across P sources, the maize monocrop, M/L intercrop and L-M rotation had significantly more negative P balances, than CP-M rotation and M/CP intercrop. P balances, across P fertilizers, were significantly less negative in M/CP compared to M/L intercrop. Less negative P balances were recorded in CTRL treatment compared to TSP and MPR across cropping systems. M/L (CTRL and TSP) intercrop system had pronounced negative K balances. In the rotation systems, significantly less negative balances were observed when maize was rotated with chickpea compared to lupin across all P sources. Pronounced GMs were realized in M/L intercrop (TSP) followed by L-M (TSP) and lowest in M/L (TSP and CTRL). The N, P and K nutrient balances in response to P sources and cropping systems exhibited a negative relationship with crop GM. The positive GMs obtained were thus at the expense of soil nutrient mining as treatments with high nutrient losses, case for N and P, had the highest GMs. Considering nutrient balance studies alongside economic analysis has thus demonstrated the hidden environmental costs in the positive crop GMs and by extension the efficiency of such production systems. As a result, increased GMs under introduced technologies are not sustainable unless the same is matched with adequate nutrient replenishments to balance those lost through harvested products and other nutrient loss pathways. Farmers would, actually, go for those technologies that not only maximize yields but also accrue high profits. In the context of this study, and in order of GM (from highest) analysis, M/L intercrop, maize monocrop and L-M rotation with application of TSP are such technologies. In the long-run however these technologies will prove untenable due to nutrient mining. Nonetheless to guarantee efficient production and sustainable maize systems, following application of P fertilizer and legume integration, it is important that profits accrued from farm sales be used to purchase fertilizers and/or support practices geared towards replenishing mined soil nutrients. This way farm profits realized will not be at the expense of nutrient mining. Keywords: Cropping systems; gross margins; Kabete sub-County; MonQi; Nutrient Balances; Rock phosphates

White Lupin (Lupinus albus L. cv. Amiga) Increases Solubility of Minjingu Phosphate Rock, Phosphorus Balances and Maize Yields in Njoro Kenya

Exudation of high amounts of citrate in white lupin (Lupinus albus L. cv. Amiga) has the advantage of being effective in mobilization of a wide range of sparingly soluble P sources. To improve cultivation system of maize, a field experiment was conducted to assess effectiveness of white lupin (Lupinus albus L. cv. Amiga) in increasing solubility of minjingu phosphate rock (MPR), phosphorus balances and maize yields in Njoro sub-County, Kenya. The randomized complete block design experiment was conducted for four seasons; short (October – February) and long rain seasons (March-September) of 2010 and 2011. The treatments were; (i) fallow (F) – maize (M) rotation with triple superphosphate (TSP) applied (MTSP- F), (ii) fallow - maize rotation with MPR applied (MMPR –F), (iii) lupin (L) – maize rotation with MPR applied (MMPR- L) and (iv) maize/lupin intercrop with MPR applied (M/LMPR – F). Soil and plant P and maize grain yield were higher in M/LMPR – F (with additional lupin grain yield) and MTSP– F treatments. All treatments resulted in positive P balances at the end of two years with highest values in MTSP– F treatment and lowest in M/LMPR – F. Intercropping lupin with maize amid application of MPR is recommended for enhanced maize performance in the farming systems of resource poor farmers. Measurement of available soil nitrogen and comparison of lupin with other legumes in solubilizing MPR is recommended

Comparative Effects of Soil Amendments on Phosphorus Use and Agronomic Efficiencies of Two Maize Hybrids in Acidic Soils of Molo County, Kenya

The deficiency of P and the shortened growing seasons due to climate change are identified constraints in the production of commonly grown long maturing maize hybrid (H614) in the acid soils of Molo County, Kenya. The current study therefore investigated (i) the effect of soil amendments; lime (L), minjingu phosphate rock (MPR) and manure (FYM) on soil available P and its uptake, phosphorus use efficiency (PUE) and maize grain yield of long (H614) and short (H513) maturing maize hybrids and (ii) the relative agronomic efficiency (RAE) of MPR. Field experiments were set up at the Kenya Agricultural Research Institute, Molo during the long rain seasons of 2009 and 2010. A randomized complete block design with a 23 factorial arrangement was used for the first objective. The factors, each at two levels, were L (0 and 3 t ha-1), MPR (0 and 60 kg P ha-1) and FYM (0 and 5 t ha-1) giving a total of eight treatments; C (control), L, MPR, FYM, L+MPR, L+FYM, FYM+MPR and L+FYM+MPR. The relative agronomic efficiency (RAE) of MPR was determined in a parallel experiment laid out in randomized complete block design with a split plot arrangement and replicated thrice. Maize hybrid H513 and H614 were the test crops in both experiments and constituted the main plots. The split plots were control (0 kg P ha-1), triple super phosphate (60 kg P ha-1) and MPR (60 kg P ha-1). Soil available P and its uptake, PUE, RAE and maize yields were the parameters measured. The application of soil amendments increased soil available P and its uptake, PUE and maize yields over the control for both maize hybrids. Highest values of the measured parameters were recorded in the L+FYM+MPR treatment and for maize hybrid H614. The two year mean values of relative agronomic efficiency RAE (%) of MPR were 60 (H513) and 66.7 (H614), and significantly higher for the maize hybrid H614. The combined application of soil amendments could thus improve maize productivity and is recommended for the acid soils of Molo County. The maize hybrid H513 though with lower yields, matured faster than H614 and would thus come in handy as an adaptation strategy in the face of climate change and variability. Moreover, it has a low P requirement and a short growth cycle thus making it an ideal variety, economically, for smallholder farmers

Influence of Amendments Added to Acid Soils on Biochemical Properties, Nitrogen Uptake and Hybrid Maize Yields in Nakuru County, Kenya

Aim: The current study investigated effect of soil amendments; lime (L), manure (FYM) and minjingu phosphate rock (PR) added to soils on soil microbial biomass carbon and nitrogen (SMB-C and SMB-N), available soil nitrogen (N), crop N uptake and grain yields of two maize hybrids (H513 and H614). Study Design: Two experiments, one for each maize hybrid as test crop, were laid out in a randomized complete block design with a 23 factorial arrangement. The factors each at two levels were L (0 and 3 t ha-1), PR (0 and 60 kg P ha-1) and FYM (0 and 5 t ha-1) giving a total of eight treatments; L, RP, FYM, L+RP, L+FYM, RP+FYM, L+RP+FYM and control (nothing applied). Methods: Soil and plant samples for the determination of SMB-C and SMB-N, available soil N, and crop N uptake were collected at maize seedling, tasseling and physiological maturity. Place and Duration of the Study: The experiment was conducted in Molo district of Nakuru County, Kenya during the long rain seasons of 2009 and 2010. Results: SMB-C and N levels were higher in 2010 than 2009, with lower levels obtained at maize tasseling for both maize hybrids. Available soil N and crop N uptake were higher at maize seedling and declined towards maturity. Statistically significant (P<.05) increases in SMB-C and SMB-N and available soil N and uptake were obtained with the application of soil amendments over the control. In all treatments, H513 had lower N uptake than H614 at tasseling and maturity stages of maize growth and correspondingly higher available N in soil. Maize yields (t ha-1) were higher in 2010 than 2009 and in H614 than H513. The H614 yields were significantly higher (P<.05) in L+PR+FYM (3.9) and, L+PR+FYM (4.1) and L+PR (3.9) treatments in 2009 and 2010, respectively. For H513, yields were significantly higher in L+PR+FYM (2.1 and 2.4) and L+PR (1.9 and 2.1) treatments in 2009 and 2010, respectively. Conclusion: The L+PR+FYM treatment is a feasible acid soil amendment for its superiority in the measured soil and crop parameters. The H513 matured faster than H614 and because of this attribute, is a viable option in response to the diminishing rainfall amounts and unpredictable weather patterns experienced in the County

Effects of Watering Regimes and Planting Density on Taro (Colocasia esculenta) Growth, Yield, and Yield Components in Embu, Kenya

Taro (Colocasia esculenta (L.) Schott) is one of the most underutilized crops in sub-Saharan Africa and an important staple food in the tropics. Understanding its growth response under selected watering regimes and planting densities underpins this research. A study was conducted at the Kenya Agricultural and Livestock Research Organization (KALRO), Embu Research Centre, during the long rains (LR) in 2021 and the short rains (SR) in 2021–2022. A factorial experiment with a split-plot layout arranged in a completely randomized block design was used. The main factor was the irrigation levels, while the subfactor was the planting density, with three replications. The three irrigation levels were at 100%, 60%, and 30% based on the field capacity (FC). The planting densities used were 0.5 m × 0.5 m (40,000 plants ha−1), 1 m × 0.5 m (20,000 plants ha−1), and 1 m × 1 m (10,000 plants ha−1), representative of high, medium, and low planting densities, respectively. Time and season (P<0.05) significantly influenced taro growth components (plant height, leaf area, leaf area index, and vegetative growth index) and yield components (corm length, corm diameter, corm mass, yield, and total biomass). Planting density influenced the leaf area and the leaf area index (P<0.05). The watering regime did not affect taro growth or yield components. Corm mass (0.59 kg), total biomass (49.8 t/ha), and yield (13.38 t/ha) were all the highest in the 30% FC. The 1 m × 0.5 m spacing produced the highest corm mass (0.62 kg). The high planting density (0.5 m × 0.5 m) resulted in the highest total biomass (70.2 t/ha), yield (20.84 t/ha), and harvest index (30.44%). As a result, the 0.5 m × 0.5 m planting density and 30% FC watering regime are recommended to farmers in the area for increased yields and food security

Climate Change and Variability: Farmers’ Perception, Experience and Adaptation Strategies in Makueni County, Kenya

A better understanding of climate change and variability (CCV) from the farmer’s perspective is a key to prioritizing measures to address and prepare for its consequences. A survey involving 150 farmers was thus conducted in Makueni County, Kenya to document farmers’; perception, experience and adaptation strategies to CCV. About 86% of farmers perceived CCV as a major challenge with 53% indicating that significant changes in climate would manifest in 10-20 years. Significant changes in rainfall amounts and distribution had occurred over the years and were rated by 60% of farmers as the frequently experienced aspect of CCV. About 33% of farmers had heard of but not used decision support tools (DST) to inform their agricultural activities. Workshops and seminars were reported by 67% of farmers as principal sources of information on CCV. Additionally, 50% of farmers relied on traditional knowledge for weather prediction. Only 20% of farmers had alternative strategies; agroforestry and growing drought tolerant crops particularly sorghum and cowpea, to minimize effects of CCV. Another 67% of farmers prioritized; terracing, ridging and water harvesting as adaptation strategies to minimize negative effects of CCV. The farmers were thus aware of CCV and through experience, backed with traditional technical knowledge, had gained prerequisite skills for addressing its negative effects. Nevertheless farmers’ agricultural practices could be improved by use of forecasted weather data and application of DST. Consequently enhancing farmers’ preparedness to tackle challenges posed by CCV

Effect of excessive and minimal soil moisture stress on agronomic performance of bush and climbing bean (Phaseolus vulgaris L.)

Water stress is a major crop production constraint for common bean (Phaseolus vulgaris L). The response of bush and climbing bean to excessive and minimal soil moisture at various plant growth stages was investigated under greenhouse for two growing periods; September-February 2016 and March-July 2016. The control consisted in watering with recommended rates for each plant growth stage. Two bean genotypes RWR2245 (bush bean) and MAC44 (climbing bean) were used for this study. The minimal soil moisture (drought stress) treatment consisted of withholding water supply, from the on-set of emergence, vegetative, flowering, pod setting and seed filling growth stages, up to the wilting point of plants. The excessive soil moisture (waterlogging stress) was achieved by saturating the soil on a daily basis for five successive days, starting from the on-set of the aforementioned plant growth stages. For each genotype, these treatments were replicated four times and arranged in a Completely Randomized Design. Drought stress accelerated the number of days to maturity whilst waterlogging stress tended to increase the number of days to maturity. Both stresses reduced the agronomic performance of both genotypes. However, pod setting and flowering were the most sensitive stages to drought stress and waterlogging stress, respectively