Potassium Pushes Sugarcane Yields Higher

Comprehensive research to discover what holds back sugarcane productivity in northern India has revealed that crop yield can be increased by over 15% with additional potassium.

Bitter Reality of Sugarcane Production

India is the second largest sugarcane producer in the world but struggles to achieve the levels of productivity reached by others. The history of cane cultivation in India goes back over 3,000 years. Today the crop makes up about 7% of the total agricultural output value of India and is still a major part of the socio-economic development of the rural economy. Cane helps supports millions of livelihoods on the land and, through providing the raw material for more than 500 sugar factories across India, provides employment for many millions more. The contribution of cane could be significantly higher if only the yield potential could be reached.

Understanding what holds back Sugarcane Growth

Sugarcane is, in essence, a high-performance plant. It is a perennial that produces multiple stems that grow up to 6 m high. It is highly efficient at converting and storing energy from the sun, and for much of the year continues to produce huge amounts of biomass, if it has the right level of warmth, water, and nutrients.

The north Indian state of Uttar Pradesh is the leading state for sugarcane production but is second for levels of yield. Factors such changing weather patterns, and more drought and floods, can be blamed. Frequent temperature fluctuations, spiking above or dropping below the optimum for sugarcane growth, have also had an effect. Most significant of all though is the degradation of farmland soil fertility caused by the significant nutrient demands of crops, including sugarcane, and the lack of a balanced fertilizer strategy to replenish the soil.

A team from the Indian Potash Institute (with support from the International Potash Institute (IPI), Switzerland) saw that best practice of nitrogen and phosphorus application for sugarcane have already been established and shared whereas sugarcane crop and soil requirements for potassium have been almost ignored.

Their study aimed to evaluate and demonstrate the contribution of potassium application in increasing sugarcane yield and profitability. They also planned to raise awareness of growers and others of the vital need to develop balanced fertilization regimes for the crop.

Why Potassium counts so much in Sugarcane

The main value of sugarcane comes from one quality aspect: sugar content. To produce high sugar content, potassium must be available. Potassium is essential in many aspects of plant development but, as it facilitates many biochemical and physiological processes, it is particularly important in carbon assimilation, sugar production and accumulation within the cane plant.

Indian sugarcane growers in Uttar Pradesh, and other states, may not be able to control the climate or local weather patterns but they can contribute to their crop’s nutrition and provide the right nutrient balance, especially the right levels for potassium, to ensure it grows and yields as well as possible.

Investigating Right Amount and Right Time for Potassium Application

The trials to test sugarcane response to different levels of potassium application took place in seven districts of western and eastern Uttar Pradesh. There were over 160 demonstration plots in fields of different farmers in each district. In fact, each demonstration was a pair of plots, with a control area lying alongside each potassium treatment.

Detailed description of 161 potash and sugarcane demonstration plot trials in the 2014-2015 and 2015-2016 growing seasons in seven Uttar Pradesh districts.

Depending on the area, as can be seen in the table above, each pair of plots got the same fertilizer application of urea and DAP. That amounted to 150 and 175 kg nitrogen/ha and 60 and 80 kg phosphorus/ha in the western and eastern districts, respectively. In addition, eastern district plots had an application of farmyard manure. While the control plots did not receive potassium fertilizer, their paired plots were applied with potassium as muriate of potash.

During the trial, routine practices such as pest management continued as per local recommendations and the weather was monitored. The main measurement carried out was of the processable sugarcane biomass at harvest. The team also carried out economic evaluations to establish the cost benefit to the growers of investing in and applying more potassium fertilizer.

Optimizing Potassium Fertilizer Strategy for Sugarcane

The results of the experiment with sugarcane across Uttar Pradesh showed that potassium applied as muriate of potash at 150 kg/ha together with usual practice of urea, DAP, and manure, resulted in a significant increase in yield of over 15% on average. The yield difference can be seen in in the figure below. The return on nutrient investment was also significant. Growers got additional net profit of over 260,000 Indian rupees per hectare from the potassium-enriched fertilizer strategy.

Figure showing mean sugarcane yield for control and potash-applied plots. Values represent all 161 demonstration plots in seven districts of Uttar Pradesh. Bars indicate SE.

Despite these promising results, the researchers were well aware of one yield reality. Even though a substantial yield increase was achieved, to 72 Mg/ha, which for Uttar Pradesh takes it to being on a par with the best in India, it is still far below that of many other sugarcane-producing countries which, according to the United Nations Food and Agriculture Organization, usually achieve 100-130 Mg/ha. So, what is causing this yield gap? To try to find the answer, the team did a deep dive into the weather conditions during the trial.

The Impact of Weather on Sugarcane Yields

You name the weather problem and Indian sugarcane seems to suffer from it. In both regions of Uttar Pradesh where the sugarcane response to fertilizer treatments was studied, the growing season is only up to 5 months long, July-November. Before that there were spikes in temperature, much higher than the optimum range of 32-38°C, and then after it, December-January, the temperatures regularly plunge to sub-zero levels. These factors probably interrupt key growth stages such as germination, tillering and early growth.

It is not just the temperature that takes its toll on the perennial sugarcane. During the trial the monsoon period lasted two months longer in the east than in the western districts of the state.

However, even taking the local environmental conditions and negative effects on overall yield into consideration, it is still very evident from the trial that potassium application was beneficial. Applying potassium in addition to commonly applied nitrogen and phosphorus significantly increased sugarcane yield over a broad range of the plots, despite the weather.

The results gave the researchers the evidence needed to strongly recommend potassium application to sugarcane of 150 kg K₂O/ha to increase yield and profit.

For more detail about this research see the full report in the e-ifc published by the International Potash Institute (IPI).