Abstract
Ravines represent an extreme form of land degradation. Soil and moisture saving techniques (SMSTs) have been identified as effective strategies for improving the fertility of degraded lands. Three SMSTs viz., intercrop of cow pea and castor on bench terrace (SCCBT) ii) bench terrace (SBT) iii) staggered trenches on natural slope (SSTS) and iv) sapota on natural slope (Control) were imposed to observe their impact on Sapota yield and quality, runoff, soil loss, and soil properties under rain-fed conditions during 2018-20. SMSTs have significantly affected plant growth, yield and quality and soil loss-runoff in degraded ravines. The highest tree height was observed in SBT on par with SCCBT and SSTS, and lowest in SS. Similar trend was observed in case canopy spread, canopy volume and collar diameter. Among the treatments, SCCBT recorded highest yield (38.3 kg tree-1) followed by SBT, SST and lowest in SS (16.8 kg tree-1). Pulp weight (55.55 g) and vitamin C (14.69 mg) was recorded higher in SCCBT and lowest in SS. SCCBT treatment reduced runoff by 44% and it was highest in SS. Despite this SCCBT exhibited significant higher soil loss. Terracing and trenches exhibited remarkable effect on EC, SOC, available major nutrients (NPK) compared to control. SCCBT and SBT treatments significantly had higher soil moisture (%) compare to control. Hence, the cultivation of sapota after implementing terracing and staggered trenches on natural slopes proves to be a viable approach for effectively utilizing degraded ravines while promoting productivity.
Key words: Bench terraces, canopy volume, fruit quality, runoff, soil loss, soil nutrients, ravines Introduction
Ravines are often considered to be one of the most degraded forms of landscapes in drylands. In India, an estimated 4.32 M ha of land is affected by ravines (Kar et al., 2009). They are formed by water erosion that imparts soil erosion, nutrient depletion, eventually declined soil fertility and moisture retention. Stream bank erosion is one of the prime sources of land degradation in ravine areas. This erosion deteriorates drainage systems, which ultimately results in natural catastrophe such as floods, and non-point source pollution in the affected areas. Improper land use practices such as over-cultivation, tillage, and land clearance can disturb the soil structure and make the land prone soil erosion (Martínez-Hernández et al., 2017). Illicit mining activities can lead to the removal of green cover and destabilization of slopes, resulting in increased soil erosion rates (Sahu & Dash, 2011). Uncontrolled grazing can also cause soil compaction and trampling, which can damage vegetation cover and expose the soil to erosion (Sharma, 1997; Rodrigo-Comino et al., 2017). Deforestation is another major cause of soil erosion, as it can remove the protective cover provided by trees and vegetation (Keesstra, 2007; Sikka et al., 2016). Land use change, such as transformation of natural forests or grasslands to agricultural land, can also contribute to increased soil erosion rates (Navar & Synnott, 2000).
Soil erosion lead to the loss of surface-top soil, which is rich in SOM and essential nutrients, are indispensable for plant growth (Jinger & Kakade, 2019). It also changes soil texture, structure, and nutrient content, which can further affect plant growth and ecosystem function. These changes have long-term impacts on soil fertility, and soil degradation thereby. Consequently, results in reduced plant growth, crop productivity and fruit quality, and can alter the structure and function of ecosystems (Lal, 2001; Atucha et al., 2013). Nutrient and moisture deficit, soil compaction, and high summer temperatures further negatively affect plant growth and crop productivity in ravines. In addition, biotic stressors such as pest and diseases also reduce crop yields in these areas (Jinger et al., 2022). Therefore, vegetation in ravine lands faces multiple stresses both biotic and abiotic. Combination of stress events can create an uneconomical and challenging environment for farmers practicing agriculture in ravine lands. Further, effects of climatic variability, such as increased rainfall and its intensity, further exacerbate soil erosion rates in many areas including ravines, leading to additional challenges for farmers and communities (Adams et al., 2020; Blenkinsop et al., 2021; Tabari, 2020). In addition, changes in temperature and precipitation patterns can also affect vegetation growth and post monsoon soil moisture availability. This could have significant implications for global food security, as erosion can lead to reduced crop yields and soil degradation. Soil degradation, including erosion, exerts a detrimental influence on the growth of plants, their yield, and the quality of their fruits (Prakash et al., 2011; Jinger et al., 2023). Panigrahi et al., (2017) reported reduction in yield and productivity of mandarin on lands having 12% slopes under water stress areas. Therefore, enhancing productivity of such lands under changing climatic scenarios would pose serious challenges.
Soil and moisture saving techniques (SMSTs) such as bunding, terracing, trenches, and in situ water conservation etc. found potent in enhancing the productivity of ravines and improving their climate resilience (Kurothe et al., 2014). Panigrahi, et al. (2009) reported that continuous bunding, continuous trenching, and staggered trenching between rows helpful in minimizing runoff, soil loss, and nutrient loss, while enhancing growth, yield, and fruit quality of Nagpur mandarin grown in sloppy lands under drought prone areas. These measures assist in saving precious soil and water resources, improving soil quality by conserving moisture and nutrient rich top soils (Dagnachew et al., 2020; Kumar et al., 2020a; Moradi et al., 2014). Studies have shown that SMSTs are proven to mitigate surface runoff, soil and nutrients loss, and to improve vegetative growth, yield, and fruit quality (Liu et al., 2012; Mahajan et al., 2021; Moradi et al., 2014; Jinger et al., 2023).
However, there is a lack of extensive research focusing on the potential of resilient perennial fruit crops and SMSTs to enhance productivity in degraded ravines, while also improving the yield and quality of fruit crops in erosion-prone areas in sustainable manner. Existing studies have identified certain fruit crops suitable for marginal lands near ravines, but they have not specifically addressed the challenges faced by ravine slopes in rain-fed environments (Parandiyal et al., 2018; Kumar et al., 2020c). As a result, the potential of hardy perennial fruit crops and SMSTs remains largely unexplored on a large scale for ravine slopes, primarily due to the adverse conditions found in these areas. Implementation of technologies which are sustainable under these situations, have less water and nutrient demands, and potential to conserve resources like water, nutrients, and soil will provide satisfying assurance to improve the productivity and impart substitute source of remuneration to the farmers in ravines. Moreover, it is crucial to promptly identify suitable crops and SMSTs for ravine lands. Failure to address these issues may result in the encroachment of fertile and cultivable lands by ravine heads.
Sapota (Manilkara zapota L.) is hardy, perennial fruit crop having good adaptation capacity to various abiotic stresses. Increased leaf succulence, accumulation of compatible solutes, and strong root distribution makes sapota better choice different agro-ecological regions. Therefore, it flourishes well from semi-arid tropics with scanty rainfall to humid coastal regions (Rahman et al., 2019). Presence of latex and tannins in leaves and fruits makes sapota less preferred choice to wild animals. Therefore, bringing degraded ravines under cultivation of sapota with the advantages of SMSTs will help to reduce adverse impact of harsh conditions on crop growth, while improving the productivity and resilience. With this background, following objectives were set to explore the effectiveness of SMSTs in sapota.
To determine the impact of SMSTs on plant growth, fruit yield and quality of rainfed sapota grown in ravines.
To assess the effectiveness of SMSTs on soil erosion, runoff loss, soil fertility and post monsoon moisture status.